Allow DbViewModel work on things other than lists.

and use it for blogs

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -30,6 +30,7 @@ import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.android.account.DozeHelperModule;
 import org.briarproject.briar.android.account.LockManagerImpl;
 import org.briarproject.briar.android.account.SetupModule;
+import org.briarproject.briar.android.blog.BlogModule;
 import org.briarproject.briar.android.contact.ContactListModule;
 import org.briarproject.briar.android.forum.ForumModule;
 import org.briarproject.briar.android.introduction.IntroductionModule;
@@ -85,6 +86,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		ContactListModule.class,
 		IntroductionModule.class,
 		// below need to be within same scope as ViewModelProvider.Factory
+		BlogModule.class,
 		ForumModule.class,
 		GroupListModule.class,
 		GroupConversationModule.class,

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -11,10 +11,8 @@ import org.briarproject.briar.android.account.SetupActivity;
 import org.briarproject.briar.android.account.UnlockActivity;
 import org.briarproject.briar.android.blog.BlogActivity;
 import org.briarproject.briar.android.blog.BlogFragment;
-import org.briarproject.briar.android.blog.BlogModule;
 import org.briarproject.briar.android.blog.BlogPostFragment;
 import org.briarproject.briar.android.blog.FeedFragment;
-import org.briarproject.briar.android.blog.FeedPostFragment;
 import org.briarproject.briar.android.blog.ReblogActivity;
 import org.briarproject.briar.android.blog.ReblogFragment;
 import org.briarproject.briar.android.blog.RssFeedImportActivity;
@@ -85,7 +83,6 @@ import dagger.Component;
 @ActivityScope
 @Component(modules = {
 		ActivityModule.class,
-		BlogModule.class,
 		CreateGroupModule.class,
 		GroupInvitationModule.class,
 		GroupMemberModule.class,
@@ -152,8 +149,6 @@ public interface ActivityComponent {
 
 	void inject(BlogPostFragment fragment);
 
-	void inject(FeedPostFragment fragment);
-
 	void inject(ReblogFragment fragment);
 
 	void inject(ReblogActivity activity);

briar-android/src/main/java/org/briarproject/briar/android/blog/BaseController.java

@@ -1,48 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.controller.handler.ExceptionHandler;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-import org.briarproject.briar.api.blog.BlogPostHeader;
-
-import java.util.Collection;
-
-import javax.annotation.Nullable;
-
-import androidx.annotation.UiThread;
-
-@NotNullByDefault
-interface BaseController {
-
-	@UiThread
-	void onStart();
-
-	@UiThread
-	void onStop();
-
-	void loadBlogPosts(GroupId g,
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler);
-
-	void loadBlogPost(BlogPostHeader header,
-			ResultExceptionHandler<BlogPostItem, DbException> handler);
-
-	void loadBlogPost(GroupId g, MessageId m,
-			ResultExceptionHandler<BlogPostItem, DbException> handler);
-
-	void repeatPost(BlogPostItem item, @Nullable String comment,
-			ExceptionHandler<DbException> handler);
-
-	@NotNullByDefault
-	interface BlogListener {
-
-		@UiThread
-		void onBlogPostAdded(BlogPostHeader header, boolean local);
-
-		@UiThread
-		void onBlogRemoved();
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/BaseControllerImpl.java

@@ -1,209 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import org.briarproject.bramble.api.db.DatabaseExecutor;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.identity.IdentityManager;
-import org.briarproject.bramble.api.identity.LocalAuthor;
-import org.briarproject.bramble.api.lifecycle.LifecycleManager;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.controller.DbControllerImpl;
-import org.briarproject.briar.android.controller.handler.ExceptionHandler;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-import org.briarproject.briar.api.android.AndroidNotificationManager;
-import org.briarproject.briar.api.blog.Blog;
-import org.briarproject.briar.api.blog.BlogCommentHeader;
-import org.briarproject.briar.api.blog.BlogManager;
-import org.briarproject.briar.api.blog.BlogPostHeader;
-import org.briarproject.briar.util.HtmlUtils;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-
-import androidx.annotation.CallSuper;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logDuration;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.LogUtils.now;
-import static org.briarproject.briar.util.HtmlUtils.ARTICLE;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-abstract class BaseControllerImpl extends DbControllerImpl
-		implements BaseController, EventListener {
-
-	private static final Logger LOG =
-			Logger.getLogger(BaseControllerImpl.class.getName());
-
-	protected final EventBus eventBus;
-	protected final AndroidNotificationManager notificationManager;
-	protected final IdentityManager identityManager;
-	protected final BlogManager blogManager;
-
-	private final Map<MessageId, String> textCache = new ConcurrentHashMap<>();
-	private final Map<MessageId, BlogPostHeader> headerCache =
-			new ConcurrentHashMap<>();
-
-	BaseControllerImpl(@DatabaseExecutor Executor dbExecutor,
-			LifecycleManager lifecycleManager, EventBus eventBus,
-			AndroidNotificationManager notificationManager,
-			IdentityManager identityManager, BlogManager blogManager) {
-		super(dbExecutor, lifecycleManager);
-		this.eventBus = eventBus;
-		this.notificationManager = notificationManager;
-		this.identityManager = identityManager;
-		this.blogManager = blogManager;
-	}
-
-	@Override
-	@CallSuper
-	public void onStart() {
-		eventBus.addListener(this);
-	}
-
-	@Override
-	@CallSuper
-	public void onStop() {
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void loadBlogPosts(GroupId groupId,
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler) {
-		runOnDbThread(() -> {
-			try {
-				Collection<BlogPostItem> items = loadItems(groupId);
-				handler.onResult(items);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	Collection<BlogPostItem> loadItems(GroupId groupId) throws DbException {
-		long start = now();
-		Collection<BlogPostHeader> headers =
-				blogManager.getPostHeaders(groupId);
-		logDuration(LOG, "Loading headers", start);
-		Collection<BlogPostItem> items = new ArrayList<>(headers.size());
-		start = now();
-		for (BlogPostHeader h : headers) {
-			headerCache.put(h.getId(), h);
-			BlogPostItem item = getItem(h);
-			items.add(item);
-		}
-		logDuration(LOG, "Loading bodies", start);
-		return items;
-	}
-
-	@Override
-	public void loadBlogPost(BlogPostHeader header,
-			ResultExceptionHandler<BlogPostItem, DbException> handler) {
-
-		String text = textCache.get(header.getId());
-		if (text != null) {
-			LOG.info("Loaded text from cache");
-			handler.onResult(new BlogPostItem(header, text));
-			return;
-		}
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				BlogPostItem item = getItem(header);
-				logDuration(LOG, "Loading text", start);
-				handler.onResult(item);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	@Override
-	public void loadBlogPost(GroupId g, MessageId m,
-			ResultExceptionHandler<BlogPostItem, DbException> handler) {
-
-		BlogPostHeader header = headerCache.get(m);
-		if (header != null) {
-			LOG.info("Loaded header from cache");
-			loadBlogPost(header, handler);
-			return;
-		}
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				BlogPostHeader header1 = getPostHeader(g, m);
-				BlogPostItem item = getItem(header1);
-				logDuration(LOG, "Loading post", start);
-				handler.onResult(item);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	@Override
-	public void repeatPost(BlogPostItem item, @Nullable String comment,
-			ExceptionHandler<DbException> handler) {
-		runOnDbThread(() -> {
-			try {
-				LocalAuthor a = identityManager.getLocalAuthor();
-				Blog b = blogManager.getPersonalBlog(a);
-				BlogPostHeader h = item.getHeader();
-				blogManager.addLocalComment(a, b.getId(), comment, h);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	private BlogPostHeader getPostHeader(GroupId g, MessageId m)
-			throws DbException {
-		BlogPostHeader header = headerCache.get(m);
-		if (header == null) {
-			header = blogManager.getPostHeader(g, m);
-			headerCache.put(m, header);
-		}
-		return header;
-	}
-
-	@DatabaseExecutor
-	private BlogPostItem getItem(BlogPostHeader h) throws DbException {
-		String text;
-		if (h instanceof BlogCommentHeader) {
-			BlogCommentHeader c = (BlogCommentHeader) h;
-			BlogCommentItem item = new BlogCommentItem(c);
-			text = getPostText(item.getPostHeader().getId());
-			item.setText(text);
-			return item;
-		} else {
-			text = getPostText(h.getId());
-			return new BlogPostItem(h, text);
-		}
-	}
-
-	@DatabaseExecutor
-	private String getPostText(MessageId m) throws DbException {
-		String text = textCache.get(m);
-		if (text == null) {
-			text = HtmlUtils.clean(blogManager.getPostText(m), ARTICLE);
-			textCache.put(m, text);
-		}
-		return text;
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/BasePostFragment.java

@@ -1,121 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import android.content.Intent;
-import android.os.Bundle;
-import android.os.Handler;
-import android.os.Looper;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ProgressBar;
-
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.fragment.BaseFragment;
-
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-
-import androidx.annotation.CallSuper;
-import androidx.annotation.UiThread;
-
-import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
-import static android.view.View.INVISIBLE;
-import static android.view.View.VISIBLE;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
-import static org.briarproject.briar.android.util.UiUtils.MIN_DATE_RESOLUTION;
-
-@UiThread
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-abstract class BasePostFragment extends BaseFragment {
-
-	static final String POST_ID = "briar.POST_ID";
-
-	private static final Logger LOG =
-			getLogger(BasePostFragment.class.getName());
-
-	private final Handler handler = new Handler(Looper.getMainLooper());
-
-	protected MessageId postId;
-	private ProgressBar progressBar;
-	private BlogPostViewHolder ui;
-	private BlogPostItem post;
-	private Runnable refresher;
-
-	@CallSuper
-	@Nullable
-	@Override
-	public View onCreateView(LayoutInflater inflater,
-			@Nullable ViewGroup container,
-			@Nullable Bundle savedInstanceState) {
-		// retrieve MessageId of blog post from arguments
-		byte[] p = requireArguments().getByteArray(POST_ID);
-		if (p == null) throw new IllegalStateException("No post ID in args");
-		postId = new MessageId(p);
-
-		View view = inflater.inflate(R.layout.fragment_blog_post, container,
-				false);
-		progressBar = view.findViewById(R.id.progressBar);
-		progressBar.setVisibility(VISIBLE);
-		ui = new BlogPostViewHolder(view, true, new OnBlogPostClickListener() {
-			@Override
-			public void onBlogPostClick(BlogPostItem post) {
-				// We're already there
-			}
-
-			@Override
-			public void onAuthorClick(BlogPostItem post) {
-				if (getContext() == null) return;
-				Intent i = new Intent(getContext(), BlogActivity.class);
-				i.putExtra(GROUP_ID, post.getGroupId().getBytes());
-				i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-				getContext().startActivity(i);
-			}
-		}, getFragmentManager());
-		return view;
-	}
-
-	@CallSuper
-	@Override
-	public void onStart() {
-		super.onStart();
-		startPeriodicUpdate();
-	}
-
-	@CallSuper
-	@Override
-	public void onStop() {
-		super.onStop();
-		stopPeriodicUpdate();
-	}
-
-	@UiThread
-	protected void onBlogPostLoaded(BlogPostItem post) {
-		progressBar.setVisibility(INVISIBLE);
-		this.post = post;
-		ui.bindItem(post);
-	}
-
-	private void startPeriodicUpdate() {
-		refresher = () -> {
-			LOG.info("Updating Content...");
-			ui.updateDate(post.getTimestamp());
-			handler.postDelayed(refresher, MIN_DATE_RESOLUTION);
-		};
-		LOG.info("Adding Handler Callback");
-		handler.postDelayed(refresher, MIN_DATE_RESOLUTION);
-	}
-
-	private void stopPeriodicUpdate() {
-		if (refresher != null) {
-			LOG.info("Removing Handler Callback");
-			handler.removeCallbacks(refresher);
-		}
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/BaseViewModel.java

@@ -0,0 +1,199 @@
+package org.briarproject.briar.android.blog;
+
+import android.app.Application;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveResult;
+import org.briarproject.briar.api.android.AndroidNotificationManager;
+import org.briarproject.briar.api.blog.Blog;
+import org.briarproject.briar.api.blog.BlogCommentHeader;
+import org.briarproject.briar.api.blog.BlogManager;
+import org.briarproject.briar.api.blog.BlogPostHeader;
+import org.briarproject.briar.util.HtmlUtils;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+
+import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.LogUtils.now;
+import static org.briarproject.briar.util.HtmlUtils.ARTICLE;
+
+@NotNullByDefault
+abstract class BaseViewModel extends DbViewModel implements EventListener {
+
+	private static final Logger LOG = getLogger(BaseViewModel.class.getName());
+
+	private final EventBus eventBus;
+	protected final IdentityManager identityManager;
+	protected final AndroidNotificationManager notificationManager;
+	protected final BlogManager blogManager;
+
+	protected final MutableLiveData<LiveResult<ListUpdate>> blogPosts =
+			new MutableLiveData<>();
+
+	BaseViewModel(Application application,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
+			EventBus eventBus,
+			IdentityManager identityManager,
+			AndroidNotificationManager notificationManager,
+			BlogManager blogManager) {
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
+		this.eventBus = eventBus;
+		this.identityManager = identityManager;
+		this.notificationManager = notificationManager;
+		this.blogManager = blogManager;
+		eventBus.addListener(this);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		eventBus.removeListener(this);
+	}
+
+	@DatabaseExecutor
+	protected List<BlogPostItem> loadBlogPosts(Transaction txn, GroupId groupId)
+			throws DbException {
+		long start = now();
+		List<BlogPostHeader> headers =
+				blogManager.getPostHeaders(txn, groupId);
+		logDuration(LOG, "Loading headers", start);
+		List<BlogPostItem> items = new ArrayList<>(headers.size());
+		start = now();
+		for (BlogPostHeader h : headers) {
+			BlogPostItem item = getItem(txn, h);
+			items.add(item);
+		}
+		logDuration(LOG, "Loading bodies", start);
+		return items;
+	}
+
+	@DatabaseExecutor
+	protected BlogPostItem getItem(Transaction txn, BlogPostHeader h)
+			throws DbException {
+		String text;
+		if (h instanceof BlogCommentHeader) {
+			BlogCommentHeader c = (BlogCommentHeader) h;
+			BlogCommentItem item = new BlogCommentItem(c);
+			text = getPostText(txn, item.getPostHeader().getId());
+			item.setText(text);
+			return item;
+		} else {
+			text = getPostText(txn, h.getId());
+			return new BlogPostItem(h, text);
+		}
+	}
+
+	@DatabaseExecutor
+	private String getPostText(Transaction txn, MessageId m)
+			throws DbException {
+		return HtmlUtils.clean(blogManager.getPostText(txn, m), ARTICLE);
+	}
+
+	LiveData<LiveResult<BlogPostItem>> loadBlogPost(GroupId g, MessageId m) {
+		MutableLiveData<LiveResult<BlogPostItem>> result =
+				new MutableLiveData<>();
+		runOnDbThread(true, txn -> {
+			long start = now();
+			BlogPostHeader header = blogManager.getPostHeader(txn, g, m);
+			BlogPostItem item = getItem(txn, header);
+			logDuration(LOG, "Loading post", start);
+			result.postValue(new LiveResult<>(item));
+		}, e -> {
+			logException(LOG, WARNING, e);
+			result.postValue(new LiveResult<>(e));
+		});
+		return result;
+	}
+
+	protected void onBlogPostAdded(BlogPostHeader header, boolean local) {
+		runOnDbThread(true, txn -> {
+			BlogPostItem item = getItem(txn, header);
+			txn.attach(() -> onBlogPostItemAdded(item, local));
+		}, this::handleException);
+	}
+
+	@UiThread
+	private void onBlogPostItemAdded(BlogPostItem item, boolean local) {
+		List<BlogPostItem> items = addListItem(getBlogPostItems(), item);
+		if (items != null) {
+			Collections.sort(items);
+			blogPosts.setValue(new LiveResult<>(new ListUpdate(local, items)));
+		}
+	}
+
+	void repeatPost(BlogPostItem item, @Nullable String comment) {
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor a = identityManager.getLocalAuthor();
+				Blog b = blogManager.getPersonalBlog(a);
+				BlogPostHeader h = item.getHeader();
+				blogManager.addLocalComment(a, b.getId(), comment, h);
+			} catch (DbException e) {
+				handleException(e);
+			}
+		});
+	}
+
+	LiveData<LiveResult<ListUpdate>> getBlogPosts() {
+		return blogPosts;
+	}
+
+	@UiThread
+	protected List<BlogPostItem> getBlogPostItems() {
+		LiveResult<ListUpdate> value = blogPosts.getValue();
+		if (value == null) return null;
+		ListUpdate result = value.getResultOrNull();
+		return result == null ? null : result.getItems();
+	}
+
+	static class ListUpdate {
+
+		@Nullable
+		private final Boolean postAddedWasLocal;
+		private final List<BlogPostItem> items;
+
+		ListUpdate(@Nullable Boolean postAddedWasLocal,
+				List<BlogPostItem> items) {
+			this.postAddedWasLocal = postAddedWasLocal;
+			this.items = items;
+		}
+
+		@Nullable
+		public Boolean getPostAddedWasLocal() {
+			return postAddedWasLocal;
+		}
+
+		public List<BlogPostItem> getItems() {
+			return items;
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogActivity.java

@@ -16,6 +16,9 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import androidx.appcompat.widget.Toolbar;
+import androidx.lifecycle.ViewModelProvider;
+
+import static java.util.Objects.requireNonNull;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -23,7 +26,16 @@ public class BlogActivity extends BriarActivity
 		implements BaseFragmentListener {
 
 	@Inject
-	BlogController blogController;
+	ViewModelProvider.Factory viewModelFactory;
+
+	private BlogViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(BlogViewModel.class);
+	}
 
 	@Override
 	public void onCreate(@Nullable Bundle state) {
@@ -31,32 +43,36 @@ public class BlogActivity extends BriarActivity
 
 		// GroupId from Intent
 		Intent i = getIntent();
-		byte[] b = i.getByteArrayExtra(GROUP_ID);
-		if (b == null) throw new IllegalStateException("No group ID in intent");
-		GroupId groupId = new GroupId(b);
-		blogController.setGroupId(groupId);
+		GroupId groupId =
+				new GroupId(requireNonNull(i.getByteArrayExtra(GROUP_ID)));
+		viewModel.setGroupId(groupId);
 
 		setContentView(R.layout.activity_fragment_container_toolbar);
 		Toolbar toolbar = setUpCustomToolbar(false);
 
 		// Open Sharing Status on Toolbar click
-		if (toolbar != null) {
-			toolbar.setOnClickListener(v -> {
-				Intent i1 = new Intent(BlogActivity.this,
-						BlogSharingStatusActivity.class);
-				i1.putExtra(GROUP_ID, groupId.getBytes());
-				startActivity(i1);
-			});
-		}
+		toolbar.setOnClickListener(v -> {
+			Intent i1 = new Intent(BlogActivity.this,
+					BlogSharingStatusActivity.class);
+			i1.putExtra(GROUP_ID, groupId.getBytes());
+			startActivity(i1);
+		});
+
+		viewModel.getBlog().observe(this, blog ->
+				setTitle(blog.getBlog().getAuthor().getName())
+		);
+		viewModel.getSharingInfo().observe(this, info ->
+				setToolbarSubTitle(info.total, info.online)
+		);
 
 		if (state == null) {
 			showInitialFragment(BlogFragment.newInstance(groupId));
 		}
 	}
 
-	@Override
-	public void injectActivity(ActivityComponent component) {
-		component.inject(this);
+	private void setToolbarSubTitle(int total, int online) {
+		requireNonNull(getSupportActionBar())
+				.setSubtitle(getString(R.string.shared_with, total, online));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogCommentItem.java

@@ -8,7 +8,9 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
-// This class is not thread-safe
+import javax.annotation.concurrent.NotThreadSafe;
+
+@NotThreadSafe
 class BlogCommentItem extends BlogPostItem {
 
 	private static final BlogCommentComparator COMPARATOR =

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogController.java

@@ -1,46 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-
-import java.util.Collection;
-
-import androidx.annotation.UiThread;
-
-@NotNullByDefault
-public interface BlogController extends BaseController {
-
-	void setGroupId(GroupId g);
-
-	@UiThread
-	void setBlogSharingListener(BlogSharingListener listener);
-
-	@UiThread
-	void unsetBlogSharingListener(BlogSharingListener listener);
-
-	void loadBlogPosts(
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler);
-
-	void loadBlogPost(MessageId m,
-			ResultExceptionHandler<BlogPostItem, DbException> handler);
-
-	void loadBlog(ResultExceptionHandler<BlogItem, DbException> handler);
-
-	void deleteBlog(ResultExceptionHandler<Void, DbException> handler);
-
-	void loadSharingContacts(
-			ResultExceptionHandler<Collection<ContactId>, DbException> handler);
-
-	interface BlogSharingListener extends BlogListener {
-		@UiThread
-		void onBlogInvitationAccepted(ContactId c);
-
-		@UiThread
-		void onBlogLeft(ContactId c);
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogFragment.java

@@ -1,9 +1,7 @@
 package org.briarproject.briar.android.blog;
 
-import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
-import android.os.Parcelable;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuInflater;
@@ -12,33 +10,25 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Toast;
 
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.activity.BriarActivity;
-import org.briarproject.briar.android.blog.BlogController.BlogSharingListener;
-import org.briarproject.briar.android.controller.SharingController;
-import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
+import org.briarproject.briar.android.blog.BaseViewModel.ListUpdate;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.sharing.BlogSharingStatusActivity;
 import org.briarproject.briar.android.sharing.ShareBlogActivity;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
-import org.briarproject.briar.api.blog.BlogPostHeader;
-
-import java.util.Collection;
+import org.briarproject.briar.android.widget.LinkDialogFragment;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
-import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AlertDialog;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView.LayoutManager;
 
@@ -49,30 +39,22 @@ import static com.google.android.material.snackbar.Snackbar.LENGTH_LONG;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_SHARE_BLOG;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_WRITE_BLOG_POST;
-import static org.briarproject.briar.android.controller.SharingController.SharingListener;
 
 @UiThread
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class BlogFragment extends BaseFragment
-		implements BlogSharingListener, SharingListener,
-		OnBlogPostClickListener {
+		implements OnBlogPostClickListener {
 
 	private final static String TAG = BlogFragment.class.getName();
 
 	@Inject
-	BlogController blogController;
-	@Inject
-	SharingController sharingController;
-	@Nullable
-	private Parcelable layoutManagerState;
+	ViewModelProvider.Factory viewModelFactory;
 
 	private GroupId groupId;
-	private BlogPostAdapter adapter;
-	private LayoutManager layoutManager;
+	private BlogViewModel viewModel;
+	private final BlogPostAdapter adapter = new BlogPostAdapter(false, this);
 	private BriarRecyclerView list;
-	private MenuItem writeButton, deleteButton;
-	private boolean isMyBlog = false, canDeleteBlog = false;
 
 	static BlogFragment newInstance(GroupId groupId) {
 		BlogFragment f = new BlogFragment();
@@ -87,8 +69,8 @@ public class BlogFragment extends BaseFragment
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
-		blogController.setBlogSharingListener(this);
-		sharingController.setSharingListener(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(BlogViewModel.class);
 	}
 
 	@Nullable
@@ -103,95 +85,75 @@ public class BlogFragment extends BaseFragment
 
 		View v = inflater.inflate(R.layout.fragment_blog, container, false);
 
-		adapter = new BlogPostAdapter(requireActivity(), this,
-				getFragmentManager());
 		list = v.findViewById(R.id.postList);
-		layoutManager = new LinearLayoutManager(getActivity());
+		LayoutManager layoutManager = new LinearLayoutManager(getActivity());
 		list.setLayoutManager(layoutManager);
 		list.setAdapter(adapter);
 		list.showProgressBar();
 		list.setEmptyText(getString(R.string.blogs_other_blog_empty_state));
 
-		if (savedInstanceState != null) {
-			layoutManagerState =
-					savedInstanceState.getParcelable("layoutManager");
-		}
-
+		viewModel.getBlogPosts().observe(getViewLifecycleOwner(), result ->
+				result.onError(this::handleException)
+						.onSuccess(this::onBlogPostsLoaded)
+		);
+		viewModel.getBlogRemoved().observe(getViewLifecycleOwner(), removed -> {
+			if (removed) finish();
+		});
 		return v;
 	}
 
 	@Override
 	public void onStart() {
 		super.onStart();
-		sharingController.onStart();
-		loadBlog();
-		loadSharedContacts();
-		loadBlogPosts(false);
+		viewModel.blockAndClearNotifications();
 		list.startPeriodicUpdate();
 	}
 
 	@Override
 	public void onStop() {
 		super.onStop();
-		sharingController.onStop();
+		viewModel.unblockNotifications();
 		list.stopPeriodicUpdate();
 	}
 
-	@Override
-	public void onDestroy() {
-		super.onDestroy();
-		blogController.unsetBlogSharingListener(this);
-		sharingController.unsetSharingListener(this);
-	}
-
-	@Override
-	public void onSaveInstanceState(Bundle outState) {
-		super.onSaveInstanceState(outState);
-		if (layoutManager != null) {
-			layoutManagerState = layoutManager.onSaveInstanceState();
-			outState.putParcelable("layoutManager", layoutManagerState);
-		}
-	}
-
 	@Override
 	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
 		inflater.inflate(R.menu.blogs_blog_actions, menu);
-		writeButton = menu.findItem(R.id.action_write_blog_post);
-		if (isMyBlog) writeButton.setVisible(true);
-		deleteButton = menu.findItem(R.id.action_blog_delete);
-		if (canDeleteBlog) deleteButton.setEnabled(true);
-
+		MenuItem writeButton = menu.findItem(R.id.action_write_blog_post);
+		MenuItem deleteButton = menu.findItem(R.id.action_blog_delete);
+		viewModel.getBlog().observe(getViewLifecycleOwner(), blog -> {
+			if (blog.isOurs()) writeButton.setVisible(true);
+			if (blog.canBeRemoved()) deleteButton.setEnabled(true);
+		});
 		super.onCreateOptionsMenu(menu, inflater);
 	}
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		switch (item.getItemId()) {
-			case R.id.action_write_blog_post:
-				Intent i = new Intent(getActivity(),
-						WriteBlogPostActivity.class);
-				i.putExtra(GROUP_ID, groupId.getBytes());
-				startActivityForResult(i, REQUEST_WRITE_BLOG_POST);
-				return true;
-			case R.id.action_blog_share:
-				Intent i2 = new Intent(getActivity(), ShareBlogActivity.class);
-				i2.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-				i2.putExtra(GROUP_ID, groupId.getBytes());
-				startActivityForResult(i2, REQUEST_SHARE_BLOG);
-				return true;
-			case R.id.action_blog_sharing_status:
-				Intent i3 = new Intent(getActivity(),
-						BlogSharingStatusActivity.class);
-				i3.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-				i3.putExtra(GROUP_ID, groupId.getBytes());
-				startActivity(i3);
-				return true;
-			case R.id.action_blog_delete:
-				showDeleteDialog();
-				return true;
-			default:
-				return super.onOptionsItemSelected(item);
+		int itemId = item.getItemId();
+		if (itemId == R.id.action_write_blog_post) {
+			Intent i = new Intent(getActivity(), WriteBlogPostActivity.class);
+			i.putExtra(GROUP_ID, groupId.getBytes());
+			startActivityForResult(i, REQUEST_WRITE_BLOG_POST);
+			return true;
+		} else if (itemId == R.id.action_blog_share) {
+			Intent i = new Intent(getActivity(), ShareBlogActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			i.putExtra(GROUP_ID, groupId.getBytes());
+			startActivityForResult(i, REQUEST_SHARE_BLOG);
+			return true;
+		} else if (itemId == R.id.action_blog_sharing_status) {
+			Intent i =
+					new Intent(getActivity(), BlogSharingStatusActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			i.putExtra(GROUP_ID, groupId.getBytes());
+			startActivity(i);
+			return true;
+		} else if (itemId == R.id.action_blog_delete) {
+			showDeleteDialog();
+			return true;
 		}
+		return super.onOptionsItemSelected(item);
 	}
 
 	@Override
@@ -201,7 +163,6 @@ public class BlogFragment extends BaseFragment
 
 		if (request == REQUEST_WRITE_BLOG_POST && result == RESULT_OK) {
 			displaySnackbar(R.string.blogs_blog_post_created, true);
-			loadBlogPosts(true);
 		} else if (request == REQUEST_SHARE_BLOG && result == RESULT_OK) {
 			displaySnackbar(R.string.blogs_sharing_snackbar, false);
 		}
@@ -212,35 +173,25 @@ public class BlogFragment extends BaseFragment
 		return TAG;
 	}
 
-	@Override
-	public void onBlogPostAdded(BlogPostHeader header, boolean local) {
-		blogController.loadBlogPost(header,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						adapter.add(post);
-						if (local) {
-							list.scrollToPosition(0);
-							displaySnackbar(R.string.blogs_blog_post_created,
-									false);
-						} else {
-							displaySnackbar(R.string.blogs_blog_post_received,
-									true);
-						}
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				}
-		);
+	private void onBlogPostsLoaded(ListUpdate update) {
+		adapter.submitList(update.getItems(), () -> {
+			Boolean wasLocal = update.getPostAddedWasLocal();
+			if (wasLocal != null && wasLocal) {
+				list.scrollToPosition(0);
+				displaySnackbar(R.string.blogs_blog_post_created,
+						false);
+			} else if (wasLocal != null) {
+				displaySnackbar(R.string.blogs_blog_post_received,
+						true);
+			}
+			list.showData();
+		});
 	}
 
 	@Override
 	public void onBlogPostClick(BlogPostItem post) {
-		BlogPostFragment f = BlogPostFragment.newInstance(post.getId());
+		BlogPostFragment f =
+				BlogPostFragment.newInstance(groupId, post.getId(), false);
 		showNextFragment(f);
 	}
 
@@ -256,111 +207,10 @@ public class BlogFragment extends BaseFragment
 		getContext().startActivity(i);
 	}
 
-	private void loadBlogPosts(boolean reload) {
-		blogController.loadBlogPosts(
-				new UiResultExceptionHandler<Collection<BlogPostItem>,
-						DbException>(this) {
-					@Override
-					public void onResultUi(Collection<BlogPostItem> posts) {
-						if (posts.isEmpty()) {
-							list.showData();
-						} else {
-							adapter.addAll(posts);
-							if (reload || layoutManagerState == null) {
-								list.scrollToPosition(0);
-							} else {
-								layoutManager.onRestoreInstanceState(
-										layoutManagerState);
-							}
-						}
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	private void loadBlog() {
-		blogController.loadBlog(
-				new UiResultExceptionHandler<BlogItem, DbException>(this) {
-					@Override
-					public void onResultUi(BlogItem blog) {
-						setToolbarTitle(blog.getBlog().getAuthor());
-						if (blog.isOurs())
-							showWriteButton();
-						if (blog.canBeRemoved())
-							enableDeleteButton();
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	private void setToolbarTitle(Author a) {
-		getActivity().setTitle(a.getName());
-	}
-
-	private void loadSharedContacts() {
-		blogController.loadSharingContacts(
-				new UiResultExceptionHandler<Collection<ContactId>,
-						DbException>(this) {
-					@Override
-					public void onResultUi(Collection<ContactId> contacts) {
-						sharingController.addAll(contacts);
-						int online = sharingController.getOnlineCount();
-						setToolbarSubTitle(contacts.size(), online);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
 	@Override
-	public void onBlogInvitationAccepted(ContactId c) {
-		sharingController.add(c);
-		setToolbarSubTitle(sharingController.getTotalCount(),
-				sharingController.getOnlineCount());
-	}
-
-	@Override
-	public void onBlogLeft(ContactId c) {
-		sharingController.remove(c);
-		setToolbarSubTitle(sharingController.getTotalCount(),
-				sharingController.getOnlineCount());
-	}
-
-	@Override
-	public void onSharingInfoUpdated(int total, int online) {
-		setToolbarSubTitle(total, online);
-	}
-
-	private void setToolbarSubTitle(int total, int online) {
-		ActionBar actionBar =
-				((BriarActivity) getActivity()).getSupportActionBar();
-		if (actionBar != null) {
-			actionBar.setSubtitle(
-					getString(R.string.shared_with, total, online));
-		}
-	}
-
-	private void showWriteButton() {
-		isMyBlog = true;
-		if (writeButton != null)
-			writeButton.setVisible(true);
-	}
-
-	private void enableDeleteButton() {
-		canDeleteBlog = true;
-		if (deleteButton != null)
-			deleteButton.setEnabled(true);
+	public void onLinkClick(String url) {
+		LinkDialogFragment f = LinkDialogFragment.newInstance(url);
+		f.show(getParentFragmentManager(), f.getUniqueTag());
 	}
 
 	private void displaySnackbar(int stringId, boolean scroll) {
@@ -373,38 +223,21 @@ public class BlogFragment extends BaseFragment
 	}
 
 	private void showDeleteDialog() {
-		DialogInterface.OnClickListener okListener =
-				(dialog, which) -> deleteBlog();
-		AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(),
+		AlertDialog.Builder builder = new AlertDialog.Builder(requireContext(),
 				R.style.BriarDialogTheme);
 		builder.setTitle(getString(R.string.blogs_remove_blog));
 		builder.setMessage(
 				getString(R.string.blogs_remove_blog_dialog_message));
 		builder.setPositiveButton(R.string.cancel, null);
-		builder.setNegativeButton(R.string.blogs_remove_blog_ok, okListener);
+		builder.setNegativeButton(R.string.blogs_remove_blog_ok,
+				(dialog, which) -> deleteBlog());
 		builder.show();
 	}
 
 	private void deleteBlog() {
-		blogController.deleteBlog(
-				new UiResultExceptionHandler<Void, DbException>(this) {
-					@Override
-					public void onResultUi(Void result) {
-						Toast.makeText(getActivity(),
-								R.string.blogs_blog_removed, LENGTH_SHORT)
-								.show();
-						finish();
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	@Override
-	public void onBlogRemoved() {
+		viewModel.deleteBlog();
+		Toast.makeText(getActivity(), R.string.blogs_blog_removed, LENGTH_SHORT)
+				.show();
 		finish();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogModule.java

@@ -1,35 +1,23 @@
 package org.briarproject.briar.android.blog;
 
-import org.briarproject.briar.android.activity.ActivityScope;
-import org.briarproject.briar.android.activity.BaseActivity;
-import org.briarproject.briar.android.controller.SharingController;
-import org.briarproject.briar.android.controller.SharingControllerImpl;
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
 
+import androidx.lifecycle.ViewModel;
+import dagger.Binds;
 import dagger.Module;
-import dagger.Provides;
+import dagger.multibindings.IntoMap;
 
 @Module
-public class BlogModule {
+public interface BlogModule {
 
-	@ActivityScope
-	@Provides
-	BlogController provideBlogController(BaseActivity activity,
-			BlogControllerImpl blogController) {
-		activity.addLifecycleController(blogController);
-		return blogController;
-	}
+	@Binds
+	@IntoMap
+	@ViewModelKey(FeedViewModel.class)
+	ViewModel bindFeedViewModel(FeedViewModel feedViewModel);
 
-	@ActivityScope
-	@Provides
-	FeedController provideFeedController(FeedControllerImpl feedController) {
-		return feedController;
-	}
-
-	@ActivityScope
-	@Provides
-	SharingController provideSharingController(
-			SharingControllerImpl sharingController) {
-		return sharingController;
-	}
+	@Binds
+	@IntoMap
+	@ViewModelKey(BlogViewModel.class)
+	ViewModel bindBlogViewModel(BlogViewModel blogViewModel);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostAdapter.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.blog;
 
-import android.content.Context;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -8,52 +7,44 @@ import android.view.ViewGroup;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.util.BriarAdapter;
 
-import androidx.annotation.Nullable;
-import androidx.fragment.app.FragmentManager;
+import androidx.recyclerview.widget.DiffUtil;
+import androidx.recyclerview.widget.ListAdapter;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class BlogPostAdapter extends BriarAdapter<BlogPostItem, BlogPostViewHolder> {
+class BlogPostAdapter extends ListAdapter<BlogPostItem, BlogPostViewHolder> {
 
+	private final boolean authorClickable;
 	private final OnBlogPostClickListener listener;
-	@Nullable
-	private final FragmentManager fragmentManager;
 
-	BlogPostAdapter(Context ctx, OnBlogPostClickListener listener,
-			@Nullable FragmentManager fragmentManager) {
-		super(ctx, BlogPostItem.class);
+	BlogPostAdapter(boolean authorClickable, OnBlogPostClickListener listener) {
+		super(new DiffUtil.ItemCallback<BlogPostItem>() {
+			@Override
+			public boolean areItemsTheSame(BlogPostItem a, BlogPostItem b) {
+				return a.getId().equals(b.getId());
+			}
+
+			@Override
+			public boolean areContentsTheSame(BlogPostItem a, BlogPostItem b) {
+				return a.isRead() == b.isRead();
+			}
+		});
+		this.authorClickable = authorClickable;
 		this.listener = listener;
-		this.fragmentManager = fragmentManager;
 	}
 
 	@Override
 	public BlogPostViewHolder onCreateViewHolder(ViewGroup parent,
 			int viewType) {
-		View v = LayoutInflater.from(ctx).inflate(
+		View v = LayoutInflater.from(parent.getContext()).inflate(
 				R.layout.list_item_blog_post, parent, false);
-		return new BlogPostViewHolder(v, false, listener, fragmentManager);
+		return new BlogPostViewHolder(v, false, listener, authorClickable);
 	}
 
 	@Override
 	public void onBindViewHolder(BlogPostViewHolder ui, int position) {
-		ui.bindItem(getItemAt(position));
-	}
-
-	@Override
-	public int compare(BlogPostItem a, BlogPostItem b) {
-		return a.compareTo(b);
-	}
-
-	@Override
-	public boolean areContentsTheSame(BlogPostItem a, BlogPostItem b) {
-		return a.isRead() == b.isRead();
-	}
-
-	@Override
-	public boolean areItemsTheSame(BlogPostItem a, BlogPostItem b) {
-		return a.getId().equals(b.getId());
+		ui.bindItem(getItem(position));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostFragment.java

@@ -1,76 +1,163 @@
 package org.briarproject.briar.android.blog;
 
+import android.content.Intent;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ProgressBar;
 
-import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.blog.BaseController.BlogListener;
-import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
-import org.briarproject.briar.api.blog.BlogPostHeader;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.widget.LinkDialogFragment;
 
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import androidx.annotation.UiThread;
+import androidx.lifecycle.LifecycleOwner;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static java.util.Objects.requireNonNull;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
+import static org.briarproject.briar.android.util.UiUtils.MIN_DATE_RESOLUTION;
 
-@UiThread
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class BlogPostFragment extends BasePostFragment implements BlogListener {
+public class BlogPostFragment extends BaseFragment
+		implements OnBlogPostClickListener {
 
 	private static final String TAG = BlogPostFragment.class.getName();
+	private static final Logger LOG = getLogger(TAG);
+
+	static final String POST_ID = "briar.POST_ID";
+	static final String IS_FEED = "briar.IS_FEED";
+
+	protected BlogViewModel viewModel;
+	private final Handler handler = new Handler(Looper.getMainLooper());
+
+	private ProgressBar progressBar;
+	private BlogPostViewHolder ui;
+	private BlogPostItem post;
+	private Runnable refresher;
 
 	@Inject
-	BlogController blogController;
+	ViewModelProvider.Factory viewModelFactory;
 
-	static BlogPostFragment newInstance(MessageId postId) {
+	static BlogPostFragment newInstance(GroupId blogId, MessageId postId,
+			boolean isFeed) {
 		BlogPostFragment f = new BlogPostFragment();
-
 		Bundle bundle = new Bundle();
+		bundle.putByteArray(GROUP_ID, blogId.getBytes());
 		bundle.putByteArray(POST_ID, postId.getBytes());
-
+		bundle.putBoolean(IS_FEED, isFeed);
 		f.setArguments(bundle);
 		return f;
 	}
 
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(BlogViewModel.class);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		Bundle args = requireArguments();
+		GroupId groupId =
+				new GroupId(requireNonNull(args.getByteArray(GROUP_ID)));
+		MessageId postId =
+				new MessageId(requireNonNull(args.getByteArray(POST_ID)));
+		boolean isFeed = args.getBoolean(IS_FEED);
+
+		View view = inflater.inflate(R.layout.fragment_blog_post, container,
+				false);
+		progressBar = view.findViewById(R.id.progressBar);
+		progressBar.setVisibility(VISIBLE);
+		ui = new BlogPostViewHolder(view, true, this, isFeed);
+		LifecycleOwner owner = getViewLifecycleOwner();
+		viewModel.loadBlogPost(groupId, postId).observe(owner, result ->
+				result.onError(this::handleException)
+						.onSuccess(this::onBlogPostLoaded)
+		);
+		return view;
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		startPeriodicUpdate();
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		stopPeriodicUpdate();
+	}
+
+	@UiThread
+	private void onBlogPostLoaded(BlogPostItem post) {
+		progressBar.setVisibility(INVISIBLE);
+		this.post = post;
+		ui.bindItem(post);
+	}
+
+	@Override
+	public void onBlogPostClick(BlogPostItem post) {
+		// We're already there
+	}
+
+	@Override
+	public void onAuthorClick(BlogPostItem post) {
+		Intent i = new Intent(requireContext(), BlogActivity.class);
+		i.putExtra(GROUP_ID, post.getGroupId().getBytes());
+		i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+		requireContext().startActivity(i);
+	}
+
+	@Override
+	public void onLinkClick(String url) {
+		LinkDialogFragment f = LinkDialogFragment.newInstance(url);
+		f.show(getParentFragmentManager(), f.getUniqueTag());
+	}
+
+	private void startPeriodicUpdate() {
+		refresher = () -> {
+			LOG.info("Updating Content...");
+			ui.updateDate(post.getTimestamp());
+			handler.postDelayed(refresher, MIN_DATE_RESOLUTION);
+		};
+		LOG.info("Adding Handler Callback");
+		handler.postDelayed(refresher, MIN_DATE_RESOLUTION);
+	}
+
+	private void stopPeriodicUpdate() {
+		if (refresher != null) {
+			LOG.info("Removing Handler Callback");
+			handler.removeCallbacks(refresher);
+		}
+	}
+
 	@Override
 	public String getUniqueTag() {
 		return TAG;
 	}
 
-	@Override
-	public void injectFragment(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		blogController.loadBlogPost(postId,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						onBlogPostLoaded(post);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	@Override
-	public void onBlogPostAdded(BlogPostHeader header, boolean local) {
-		// doesn't matter here
-	}
-
-	@Override
-	public void onBlogRemoved() {
-		finish();
-	}
-
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostItem.java

@@ -17,7 +17,7 @@ public class BlogPostItem implements Comparable<BlogPostItem> {
 	private final BlogPostHeader header;
 	@Nullable
 	protected String text;
-	private boolean read;
+	private final boolean read;
 
 	BlogPostItem(BlogPostHeader header, @Nullable String text) {
 		this.header = header;
@@ -74,9 +74,6 @@ public class BlogPostItem implements Comparable<BlogPostItem> {
 
 	protected static int compare(BlogPostHeader h1, BlogPostHeader h2) {
 		// The newest post comes first
-		long aTime = h1.getTimeReceived(), bTime = h2.getTimeReceived();
-		if (aTime > bTime) return -1;
-		if (aTime < bTime) return 1;
-		return 0;
+		return Long.compare(h2.getTimeReceived(), h1.getTimeReceived());
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostViewHolder.java

@@ -9,6 +9,7 @@ import android.view.ViewGroup;
 import android.widget.ImageButton;
 import android.widget.TextView;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.AuthorView;
@@ -17,23 +18,24 @@ import org.briarproject.briar.api.blog.BlogPostHeader;
 
 import javax.annotation.Nullable;
 
-import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
 import androidx.core.view.ViewCompat;
-import androidx.fragment.app.FragmentManager;
 import androidx.recyclerview.widget.RecyclerView;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
-import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
+import static org.briarproject.briar.android.blog.BlogPostFragment.POST_ID;
 import static org.briarproject.briar.android.util.UiUtils.TEASER_LENGTH;
 import static org.briarproject.briar.android.util.UiUtils.getSpanned;
 import static org.briarproject.briar.android.util.UiUtils.getTeaser;
 import static org.briarproject.briar.android.util.UiUtils.makeLinksClickable;
-import static org.briarproject.briar.api.blog.MessageType.POST;
+import static org.briarproject.briar.android.view.AuthorView.COMMENTER;
+import static org.briarproject.briar.android.view.AuthorView.REBLOGGER;
+import static org.briarproject.briar.android.view.AuthorView.RSS_FEED_REBLOGGED;
 
 @UiThread
+@NotNullByDefault
 class BlogPostViewHolder extends RecyclerView.ViewHolder {
 
 	private final Context ctx;
@@ -43,20 +45,16 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 	private final ImageButton reblogButton;
 	private final TextView text;
 	private final ViewGroup commentContainer;
-	private final boolean fullText;
+	private final boolean fullText, authorClickable;
 
-	@NonNull
 	private final OnBlogPostClickListener listener;
-	@Nullable
-	private final FragmentManager fragmentManager;
 
 	BlogPostViewHolder(View v, boolean fullText,
-			@NonNull OnBlogPostClickListener listener,
-			@Nullable FragmentManager fragmentManager) {
+			OnBlogPostClickListener listener, boolean authorClickable) {
 		super(v);
 		this.fullText = fullText;
 		this.listener = listener;
-		this.fragmentManager = fragmentManager;
+		this.authorClickable = authorClickable;
 
 		ctx = v.getContext();
 		layout = v.findViewById(R.id.postLayout);
@@ -67,10 +65,6 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		commentContainer = v.findViewById(R.id.commentContainer);
 	}
 
-	void setVisibility(int visibility) {
-		layout.setVisibility(visibility);
-	}
-
 	void hideReblogButton() {
 		reblogButton.setVisibility(GONE);
 	}
@@ -103,7 +97,7 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		author.setPersona(
 				item.isRssFeed() ? AuthorView.RSS_FEED : AuthorView.NORMAL);
 		// TODO make author clickable more often #624
-		if (!fullText && item.getHeader().getType() == POST) {
+		if (authorClickable) {
 			author.setAuthorClickable(v -> listener.onAuthorClick(item));
 		} else {
 			author.setAuthorNotClickable();
@@ -114,7 +108,7 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		if (fullText) {
 			text.setText(postText);
 			text.setTextIsSelectable(true);
-			makeLinksClickable(text, fragmentManager);
+			makeLinksClickable(text, listener::onLinkClick);
 		} else {
 			text.setTextIsSelectable(false);
 			if (postText.length() > TEASER_LENGTH)
@@ -147,17 +141,16 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 			reblogger.setAuthorClickable(v -> listener.onAuthorClick(item));
 		}
 		reblogger.setVisibility(VISIBLE);
-		reblogger.setPersona(AuthorView.REBLOGGER);
+		reblogger.setPersona(REBLOGGER);
 
 		author.setPersona(item.getHeader().getRootPost().isRssFeed() ?
-				AuthorView.RSS_FEED_REBLOGGED :
-				AuthorView.COMMENTER);
+				RSS_FEED_REBLOGGED : COMMENTER);
 
 		// comments
+		// TODO use nested RecyclerView instead like we do for Image Attachments
 		for (BlogCommentHeader c : item.getComments()) {
-			View v = LayoutInflater.from(ctx)
-					.inflate(R.layout.list_item_blog_comment,
-							commentContainer, false);
+			View v = LayoutInflater.from(ctx).inflate(
+					R.layout.list_item_blog_comment, commentContainer, false);
 
 			AuthorView author = v.findViewById(R.id.authorView);
 			TextView text = v.findViewById(R.id.textView);

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogViewModel.java

@@ -1,24 +1,24 @@
 package org.briarproject.briar.android.blog;
 
-import android.app.Activity;
+import android.app.Application;
 
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.event.GroupRemovedEvent;
-import org.briarproject.briar.android.controller.ActivityLifecycleController;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.sharing.SharingController;
+import org.briarproject.briar.android.sharing.SharingController.SharingInfo;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.Blog;
 import org.briarproject.briar.api.blog.BlogInvitationResponse;
@@ -35,85 +35,54 @@ import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 
-import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
-import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class BlogControllerImpl extends BaseControllerImpl
-		implements ActivityLifecycleController, BlogController, EventListener {
+class BlogViewModel extends BaseViewModel {
 
-	private static final Logger LOG =
-			Logger.getLogger(BlogControllerImpl.class.getName());
+	private static final Logger LOG = getLogger(BlogViewModel.class.getName());
 
 	private final BlogSharingManager blogSharingManager;
+	private final SharingController sharingController;
 
-	// UI thread
-	@Nullable
-	private BlogSharingListener listener;
+	private volatile GroupId groupId;
 
-	private volatile GroupId groupId = null;
+	private final MutableLiveData<BlogItem> blog = new MutableLiveData<>();
+	private final MutableLiveData<Boolean> blogRemoved =
+			new MutableLiveData<>();
 
 	@Inject
-	BlogControllerImpl(@DatabaseExecutor Executor dbExecutor,
-			LifecycleManager lifecycleManager, EventBus eventBus,
+	BlogViewModel(Application application,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
+			EventBus eventBus,
+			IdentityManager identityManager,
 			AndroidNotificationManager notificationManager,
-			IdentityManager identityManager, BlogManager blogManager,
-			BlogSharingManager blogSharingManager) {
-		super(dbExecutor, lifecycleManager, eventBus, notificationManager,
-				identityManager, blogManager);
+			BlogManager blogManager,
+			BlogSharingManager blogSharingManager,
+			SharingController sharingController) {
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
+				eventBus, identityManager, notificationManager, blogManager);
 		this.blogSharingManager = blogSharingManager;
-	}
-
-	@Override
-	public void onActivityCreate(Activity activity) {
-	}
-
-	@Override
-	public void onActivityStart() {
-		super.onStart();
-		notificationManager.blockNotification(groupId);
-		notificationManager.clearBlogPostNotification(groupId);
-	}
-
-	@Override
-	public void onActivityStop() {
-		super.onStop();
-		notificationManager.unblockNotification(groupId);
-	}
-
-	@Override
-	public void onActivityDestroy() {
-	}
-
-	@Override
-	public void setGroupId(GroupId g) {
-		groupId = g;
-	}
-
-	@Override
-	public void setBlogSharingListener(BlogSharingListener listener) {
-		this.listener = listener;
-	}
-
-	@Override
-	public void unsetBlogSharingListener(BlogSharingListener listener) {
-		if (this.listener == listener) this.listener = null;
+		this.sharingController = sharingController;
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (groupId == null || listener == null)
-			throw new IllegalStateException();
 		if (e instanceof BlogPostAddedEvent) {
 			BlogPostAddedEvent b = (BlogPostAddedEvent) e;
 			if (b.getGroupId().equals(groupId)) {
 				LOG.info("Blog post added");
-				listener.onBlogPostAdded(b.getHeader(), b.isLocal());
+				onBlogPostAdded(b.getHeader(), b.isLocal());
 			}
 		} else if (e instanceof BlogInvitationResponseReceivedEvent) {
 			BlogInvitationResponseReceivedEvent b =
@@ -121,41 +90,36 @@ class BlogControllerImpl extends BaseControllerImpl
 			BlogInvitationResponse r = b.getMessageHeader();
 			if (r.getShareableId().equals(groupId) && r.wasAccepted()) {
 				LOG.info("Blog invitation accepted");
-				listener.onBlogInvitationAccepted(b.getContactId());
+				sharingController.add(b.getContactId());
 			}
 		} else if (e instanceof ContactLeftShareableEvent) {
 			ContactLeftShareableEvent s = (ContactLeftShareableEvent) e;
 			if (s.getGroupId().equals(groupId)) {
 				LOG.info("Blog left by contact");
-				listener.onBlogLeft(s.getContactId());
+				sharingController.remove(s.getContactId());
 			}
 		} else if (e instanceof GroupRemovedEvent) {
 			GroupRemovedEvent g = (GroupRemovedEvent) e;
 			if (g.getGroup().getId().equals(groupId)) {
 				LOG.info("Blog removed");
-				listener.onBlogRemoved();
+				blogRemoved.setValue(true);
 			}
 		}
 	}
 
-	@Override
-	public void loadBlogPosts(
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler) {
-		if (groupId == null) throw new IllegalStateException();
-		loadBlogPosts(groupId, handler);
+	/**
+	 * Set this before calling any other methods.
+	 */
+	@UiThread
+	public void setGroupId(GroupId groupId) {
+		if (this.groupId == groupId) return; // configuration change
+		this.groupId = groupId;
+		loadBlog(groupId);
+		loadBlogPosts(groupId);
+		loadSharingContacts(groupId);
 	}
 
-	@Override
-	public void loadBlogPost(MessageId m,
-			ResultExceptionHandler<BlogPostItem, DbException> handler) {
-		if (groupId == null) throw new IllegalStateException();
-		loadBlogPost(groupId, m, handler);
-	}
-
-	@Override
-	public void loadBlog(
-			ResultExceptionHandler<BlogItem, DbException> handler) {
-		if (groupId == null) throw new IllegalStateException();
+	private void loadBlog(GroupId groupId) {
 		runOnDbThread(() -> {
 			try {
 				long start = now();
@@ -163,50 +127,65 @@ class BlogControllerImpl extends BaseControllerImpl
 				Blog b = blogManager.getBlog(groupId);
 				boolean ours = a.getId().equals(b.getAuthor().getId());
 				boolean removable = blogManager.canBeRemoved(b);
-				BlogItem blog = new BlogItem(b, ours, removable);
+				blog.postValue(new BlogItem(b, ours, removable));
 				logDuration(LOG, "Loading blog", start);
-				handler.onResult(blog);
 			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
+				handleException(e);
 			}
 		});
 	}
 
-	@Override
-	public void deleteBlog(ResultExceptionHandler<Void, DbException> handler) {
-		if (groupId == null) throw new IllegalStateException();
+	void blockAndClearNotifications() {
+		notificationManager.blockNotification(groupId);
+		notificationManager.clearBlogPostNotification(groupId);
+	}
+
+	void unblockNotifications() {
+		notificationManager.unblockNotification(groupId);
+	}
+
+	private void loadBlogPosts(GroupId groupId) {
+		loadList(txn -> new ListUpdate(null, loadBlogPosts(txn, groupId)),
+				blogPosts::setValue);
+	}
+
+	private void loadSharingContacts(GroupId groupId) {
+		runOnDbThread(true, txn -> {
+			Collection<Contact> contacts =
+					blogSharingManager.getSharedWith(txn, groupId);
+			txn.attach(() -> onSharingContactsLoaded(contacts));
+		}, this::handleException);
+	}
+
+	@UiThread
+	private void onSharingContactsLoaded(Collection<Contact> contacts) {
+		Collection<ContactId> contactIds = new ArrayList<>(contacts.size());
+		for (Contact c : contacts) contactIds.add(c.getId());
+		sharingController.addAll(contactIds);
+	}
+
+	void deleteBlog() {
 		runOnDbThread(() -> {
 			try {
 				long start = now();
 				Blog b = blogManager.getBlog(groupId);
 				blogManager.removeBlog(b);
 				logDuration(LOG, "Removing blog", start);
-				handler.onResult(null);
 			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
+				handleException(e);
 			}
 		});
 	}
 
-	@Override
-	public void loadSharingContacts(
-			ResultExceptionHandler<Collection<ContactId>, DbException> handler) {
-		if (groupId == null) throw new IllegalStateException();
-		runOnDbThread(() -> {
-			try {
-				Collection<Contact> contacts =
-						blogSharingManager.getSharedWith(groupId);
-				Collection<ContactId> contactIds =
-						new ArrayList<>(contacts.size());
-				for (Contact c : contacts) contactIds.add(c.getId());
-				handler.onResult(contactIds);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
+	LiveData<BlogItem> getBlog() {
+		return blog;
 	}
 
+	LiveData<Boolean> getBlogRemoved() {
+		return blogRemoved;
+	}
+
+	LiveData<SharingInfo> getSharingInfo() {
+		return sharingController.getSharingInfo();
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedController.java

@@ -1,32 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-import org.briarproject.briar.api.blog.Blog;
-
-import java.util.Collection;
-
-import androidx.annotation.UiThread;
-
-@NotNullByDefault
-public interface FeedController extends BaseController {
-
-	void loadBlogPosts(
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler);
-
-	void loadPersonalBlog(ResultExceptionHandler<Blog, DbException> handler);
-
-	@UiThread
-	void setFeedListener(FeedListener listener);
-
-	@UiThread
-	void unsetFeedListener(FeedListener listener);
-
-	@NotNullByDefault
-	interface FeedListener extends BlogListener {
-
-		@UiThread
-		void onBlogAdded();
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedControllerImpl.java

@@ -1,143 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import org.briarproject.bramble.api.db.DatabaseExecutor;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.NoSuchGroupException;
-import org.briarproject.bramble.api.db.NoSuchMessageException;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.bramble.api.identity.IdentityManager;
-import org.briarproject.bramble.api.lifecycle.LifecycleManager;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.sync.event.GroupAddedEvent;
-import org.briarproject.bramble.api.sync.event.GroupRemovedEvent;
-import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-import org.briarproject.briar.api.android.AndroidNotificationManager;
-import org.briarproject.briar.api.blog.Blog;
-import org.briarproject.briar.api.blog.BlogManager;
-import org.briarproject.briar.api.blog.event.BlogPostAddedEvent;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import androidx.annotation.Nullable;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logDuration;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.LogUtils.now;
-import static org.briarproject.briar.api.blog.BlogManager.CLIENT_ID;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-class FeedControllerImpl extends BaseControllerImpl implements FeedController {
-
-	private static final Logger LOG =
-			Logger.getLogger(FeedControllerImpl.class.getName());
-
-	// UI thread
-	@Nullable
-	private FeedListener listener;
-
-	@Inject
-	FeedControllerImpl(@DatabaseExecutor Executor dbExecutor,
-			LifecycleManager lifecycleManager, EventBus eventBus,
-			AndroidNotificationManager notificationManager,
-			IdentityManager identityManager, BlogManager blogManager) {
-		super(dbExecutor, lifecycleManager, eventBus, notificationManager,
-				identityManager, blogManager);
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		if (listener == null) throw new IllegalStateException();
-		notificationManager.blockAllBlogPostNotifications();
-		notificationManager.clearAllBlogPostNotifications();
-	}
-
-	@Override
-	public void onStop() {
-		super.onStop();
-		notificationManager.unblockAllBlogPostNotifications();
-	}
-
-	@Override
-	public void setFeedListener(FeedListener listener) {
-		this.listener = listener;
-	}
-
-	@Override
-	public void unsetFeedListener(FeedListener listener) {
-		if (this.listener == listener) this.listener = null;
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (listener == null) throw new IllegalStateException();
-		if (e instanceof BlogPostAddedEvent) {
-			BlogPostAddedEvent b = (BlogPostAddedEvent) e;
-			LOG.info("Blog post added");
-			listener.onBlogPostAdded(b.getHeader(), b.isLocal());
-		} else if (e instanceof GroupAddedEvent) {
-			GroupAddedEvent g = (GroupAddedEvent) e;
-			if (g.getGroup().getClientId().equals(CLIENT_ID)) {
-				LOG.info("Blog added");
-				listener.onBlogAdded();
-			}
-		} else if (e instanceof GroupRemovedEvent) {
-			GroupRemovedEvent g = (GroupRemovedEvent) e;
-			if (g.getGroup().getClientId().equals(CLIENT_ID)) {
-				LOG.info("Blog removed");
-				listener.onBlogRemoved();
-			}
-		}
-	}
-
-	@Override
-	public void loadBlogPosts(
-			ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler) {
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				Collection<BlogPostItem> posts = new ArrayList<>();
-				for (Blog b : blogManager.getBlogs()) {
-					try {
-						posts.addAll(loadItems(b.getId()));
-					} catch (NoSuchGroupException | NoSuchMessageException e) {
-						logException(LOG, WARNING, e);
-					}
-				}
-				logDuration(LOG, "Loading all posts", start);
-				handler.onResult(posts);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	@Override
-	public void loadPersonalBlog(
-			ResultExceptionHandler<Blog, DbException> handler) {
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				Author a = identityManager.getLocalAuthor();
-				Blog b = blogManager.getPersonalBlog(a);
-				logDuration(LOG, "Loading personal blog", start);
-				handler.onResult(b);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedFragment.java

@@ -2,7 +2,6 @@ package org.briarproject.briar.android.blog;
 
 import android.content.Intent;
 import android.os.Bundle;
-import android.os.Parcelable;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuInflater;
@@ -10,53 +9,41 @@ import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 
-import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.blog.FeedController.FeedListener;
-import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
+import org.briarproject.briar.android.blog.BaseViewModel.ListUpdate;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
+import org.briarproject.briar.android.widget.LinkDialogFragment;
 import org.briarproject.briar.api.blog.Blog;
-import org.briarproject.briar.api.blog.BlogPostHeader;
-
-import java.util.Collection;
-import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
-import androidx.annotation.UiThread;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.recyclerview.widget.LinearLayoutManager;
 
-import static android.app.Activity.RESULT_OK;
 import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
 import static com.google.android.material.snackbar.Snackbar.LENGTH_LONG;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
-import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_WRITE_BLOG_POST;
 
-@UiThread
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class FeedFragment extends BaseFragment implements
-		OnBlogPostClickListener, FeedListener {
+public class FeedFragment extends BaseFragment
+		implements OnBlogPostClickListener {
 
 	public final static String TAG = FeedFragment.class.getName();
-	private static final Logger LOG = Logger.getLogger(TAG);
 
 	@Inject
-	FeedController feedController;
+	ViewModelProvider.Factory viewModelFactory;
 
-	private BlogPostAdapter adapter;
+	private FeedViewModel viewModel;
+	private final BlogPostAdapter adapter = new BlogPostAdapter(true, this);
 	private LinearLayoutManager layoutManager;
 	private BriarRecyclerView list;
-	@Nullable
-	private Blog personalBlog;
-	@Nullable
-	private Parcelable layoutManagerState;
 
 	public static FeedFragment newInstance() {
 		FeedFragment f = new FeedFragment();
@@ -70,7 +57,8 @@ public class FeedFragment extends BaseFragment implements
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
-		feedController.setFeedListener(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(FeedViewModel.class);
 	}
 
 	@Nullable
@@ -82,9 +70,6 @@ public class FeedFragment extends BaseFragment implements
 
 		View v = inflater.inflate(R.layout.fragment_blog, container, false);
 
-		adapter =
-				new BlogPostAdapter(getActivity(), this, getFragmentManager());
-
 		layoutManager = new LinearLayoutManager(getActivity());
 		list = v.findViewById(R.id.postList);
 		list.setLayoutManager(layoutManager);
@@ -93,103 +78,38 @@ public class FeedFragment extends BaseFragment implements
 		list.setEmptyText(R.string.blogs_feed_empty_state);
 		list.setEmptyAction(R.string.blogs_feed_empty_state_action);
 
-		if (savedInstanceState != null) {
-			layoutManagerState =
-					savedInstanceState.getParcelable("layoutManager");
-		}
+		viewModel.getBlogPosts().observe(getViewLifecycleOwner(), result ->
+				result.onError(this::handleException)
+						.onSuccess(this::onBlogPostsLoaded)
+		);
 
 		return v;
 	}
 
-	@Override
-	public void onActivityResult(int requestCode, int resultCode,
-			@Nullable Intent data) {
-		super.onActivityResult(requestCode, resultCode, data);
-
-		// The BlogPostAddedEvent arrives when the controller is not listening
-		if (requestCode == REQUEST_WRITE_BLOG_POST && resultCode == RESULT_OK) {
-			showSnackBar(R.string.blogs_blog_post_created);
-		}
-	}
-
 	@Override
 	public void onStart() {
 		super.onStart();
-		feedController.onStart();
+		viewModel.blockAndClearAllBlogPostNotifications();
 		list.startPeriodicUpdate();
-		loadPersonalBlog();
-		loadBlogPosts(false);
 	}
 
 	@Override
 	public void onStop() {
 		super.onStop();
-		feedController.onStop();
-		adapter.clear();
-		list.showProgressBar();
+		viewModel.unblockAllBlogPostNotifications();
 		list.stopPeriodicUpdate();
-		// TODO save list position in database/preferences?
 	}
 
-	@Override
-	public void onDestroy() {
-		super.onDestroy();
-		feedController.unsetFeedListener(this);
-	}
-
-	@Override
-	public void onSaveInstanceState(Bundle outState) {
-		super.onSaveInstanceState(outState);
-		if (layoutManager != null) {
-			layoutManagerState = layoutManager.onSaveInstanceState();
-			outState.putParcelable("layoutManager", layoutManagerState);
-		}
-	}
-
-	private void loadPersonalBlog() {
-		feedController.loadPersonalBlog(
-				new UiResultExceptionHandler<Blog, DbException>(this) {
-					@Override
-					public void onResultUi(Blog b) {
-						personalBlog = b;
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	private void loadBlogPosts(boolean clear) {
-		int revision = adapter.getRevision();
-		feedController.loadBlogPosts(
-				new UiResultExceptionHandler<Collection<BlogPostItem>, DbException>(
-						this) {
-					@Override
-					public void onResultUi(Collection<BlogPostItem> posts) {
-						if (revision == adapter.getRevision()) {
-							adapter.incrementRevision();
-							if (clear) adapter.setItems(posts);
-							else adapter.addAll(posts);
-							if (posts.isEmpty()) list.showData();
-							if (layoutManagerState == null) {
-								list.scrollToPosition(0);  // Scroll to the top
-							} else {
-								layoutManager.onRestoreInstanceState(
-										layoutManagerState);
-							}
-						} else {
-							LOG.info("Concurrent update, reloading");
-							loadBlogPosts(clear);
-						}
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
+	private void onBlogPostsLoaded(ListUpdate update) {
+		adapter.submitList(update.getItems(), () -> {
+			Boolean wasLocal = update.getPostAddedWasLocal();
+			if (wasLocal != null && wasLocal) {
+				showSnackBar(R.string.blogs_blog_post_created);
+			} else if (wasLocal != null) {
+				showSnackBar(R.string.blogs_blog_post_received);
+			}
+			list.showData();
+		});
 	}
 
 	@Override
@@ -200,67 +120,48 @@ public class FeedFragment extends BaseFragment implements
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		if (personalBlog == null) return false;
-		switch (item.getItemId()) {
-			case R.id.action_write_blog_post:
-				Intent i1 =
-						new Intent(getActivity(), WriteBlogPostActivity.class);
-				i1.putExtra(GROUP_ID, personalBlog.getId().getBytes());
-				startActivityForResult(i1, REQUEST_WRITE_BLOG_POST);
-				return true;
-			case R.id.action_rss_feeds_import:
-				Intent i2 =
-						new Intent(getActivity(), RssFeedImportActivity.class);
-				startActivity(i2);
-				return true;
-			case R.id.action_rss_feeds_manage:
-				Intent i3 =
-						new Intent(getActivity(), RssFeedManageActivity.class);
-				i3.putExtra(GROUP_ID, personalBlog.getId().getBytes());
-				startActivity(i3);
-				return true;
-			default:
-				return super.onOptionsItemSelected(item);
+		int itemId = item.getItemId();
+		if (itemId == R.id.action_write_blog_post) {
+			Blog personalBlog = viewModel.getPersonalBlog().getValue();
+			if (personalBlog == null) return false;
+			Intent i = new Intent(getActivity(), WriteBlogPostActivity.class);
+			i.putExtra(GROUP_ID, personalBlog.getId().getBytes());
+			startActivity(i);
+			return true;
+		} else if (itemId == R.id.action_rss_feeds_import) {
+			Intent i = new Intent(getActivity(), RssFeedImportActivity.class);
+			startActivity(i);
+			return true;
+		} else if (itemId == R.id.action_rss_feeds_manage) {
+			Blog personalBlog = viewModel.getPersonalBlog().getValue();
+			if (personalBlog == null) return false;
+			Intent i = new Intent(getActivity(), RssFeedManageActivity.class);
+			i.putExtra(GROUP_ID, personalBlog.getId().getBytes());
+			startActivity(i);
+			return true;
 		}
-	}
-
-	@Override
-	public void onBlogPostAdded(BlogPostHeader header, boolean local) {
-		feedController.loadBlogPost(header,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						adapter.incrementRevision();
-						adapter.add(post);
-						if (local) {
-							showSnackBar(R.string.blogs_blog_post_created);
-						} else {
-							showSnackBar(R.string.blogs_blog_post_received);
-						}
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				}
-		);
+		return super.onOptionsItemSelected(item);
 	}
 
 	@Override
 	public void onBlogPostClick(BlogPostItem post) {
-		FeedPostFragment f =
-				FeedPostFragment.newInstance(post.getGroupId(), post.getId());
+		BaseFragment f = BlogPostFragment
+				.newInstance(post.getGroupId(), post.getId(), true);
 		showNextFragment(f);
 	}
 
 	@Override
 	public void onAuthorClick(BlogPostItem post) {
-		Intent i = new Intent(getContext(), BlogActivity.class);
+		Intent i = new Intent(requireContext(), BlogActivity.class);
 		i.putExtra(GROUP_ID, post.getGroupId().getBytes());
 		i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-		getContext().startActivity(i);
+		requireContext().startActivity(i);
+	}
+
+	@Override
+	public void onLinkClick(String url) {
+		LinkDialogFragment f = LinkDialogFragment.newInstance(url);
+		f.show(getParentFragmentManager(), f.getUniqueTag());
 	}
 
 	@Override
@@ -283,14 +184,4 @@ public class FeedFragment extends BaseFragment implements
 		sb.make(list, stringRes, LENGTH_LONG).show();
 	}
 
-	@Override
-	public void onBlogAdded() {
-		loadBlogPosts(false);
-	}
-
-	@Override
-	public void onBlogRemoved() {
-		loadBlogPosts(true);
-	}
-
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedPostFragment.java

@@ -1,87 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import android.os.Bundle;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.annotation.UiThread;
-
-import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
-
-@UiThread
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class FeedPostFragment extends BasePostFragment {
-
-	private static final String TAG = FeedPostFragment.class.getName();
-
-	private GroupId blogId;
-
-	@Inject
-	FeedController feedController;
-
-	static FeedPostFragment newInstance(GroupId blogId, MessageId postId) {
-		FeedPostFragment f = new FeedPostFragment();
-
-		Bundle bundle = new Bundle();
-		bundle.putByteArray(GROUP_ID, blogId.getBytes());
-		bundle.putByteArray(POST_ID, postId.getBytes());
-
-		f.setArguments(bundle);
-		return f;
-	}
-
-	@Override
-	public void injectFragment(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	@Nullable
-	@Override
-	public View onCreateView(LayoutInflater inflater,
-			@Nullable ViewGroup container,
-			@Nullable Bundle savedInstanceState) {
-		Bundle args = requireArguments();
-		byte[] b = args.getByteArray(GROUP_ID);
-		if (b == null) throw new IllegalStateException("No group ID in args");
-		blogId = new GroupId(b);
-
-		return super.onCreateView(inflater, container, savedInstanceState);
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		feedController.loadBlogPost(blogId, postId,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						onBlogPostLoaded(post);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedViewModel.java

@@ -0,0 +1,134 @@
+package org.briarproject.briar.android.blog;
+
+import android.app.Application;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.event.GroupRemovedEvent;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.viewmodel.LiveResult;
+import org.briarproject.briar.api.android.AndroidNotificationManager;
+import org.briarproject.briar.api.blog.Blog;
+import org.briarproject.briar.api.blog.BlogManager;
+import org.briarproject.briar.api.blog.event.BlogPostAddedEvent;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.now;
+import static org.briarproject.briar.api.blog.BlogManager.CLIENT_ID;
+
+@NotNullByDefault
+class FeedViewModel extends BaseViewModel {
+
+	private static final Logger LOG = getLogger(FeedViewModel.class.getName());
+
+	private final MutableLiveData<Blog> personalBlog = new MutableLiveData<>();
+
+	@Inject
+	FeedViewModel(Application application,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
+			EventBus eventBus,
+			IdentityManager identityManager,
+			AndroidNotificationManager notificationManager,
+			BlogManager blogManager) {
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
+				eventBus, identityManager, notificationManager, blogManager);
+		loadPersonalBlog();
+		loadAllBlogPosts();
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof BlogPostAddedEvent) {
+			BlogPostAddedEvent b = (BlogPostAddedEvent) e;
+			LOG.info("Blog post added");
+			onBlogPostAdded(b.getHeader(), b.isLocal());
+		}
+		if (e instanceof GroupRemovedEvent) {
+			GroupRemovedEvent g = (GroupRemovedEvent) e;
+			if (g.getGroup().getClientId().equals(CLIENT_ID)) {
+				LOG.info("Blog removed");
+				onBlogRemoved(g.getGroup().getId());
+			}
+		}
+	}
+
+	void blockAndClearAllBlogPostNotifications() {
+		notificationManager.blockAllBlogPostNotifications();
+		notificationManager.clearAllBlogPostNotifications();
+	}
+
+	void unblockAllBlogPostNotifications() {
+		notificationManager.unblockAllBlogPostNotifications();
+	}
+
+	private void loadPersonalBlog() {
+		runOnDbThread(() -> {
+			try {
+				long start = now();
+				Author a = identityManager.getLocalAuthor();
+				Blog b = blogManager.getPersonalBlog(a);
+				logDuration(LOG, "Loading personal blog", start);
+				personalBlog.postValue(b);
+			} catch (DbException e) {
+				handleException(e);
+			}
+		});
+	}
+
+	LiveData<Blog> getPersonalBlog() {
+		return personalBlog;
+	}
+
+	private void loadAllBlogPosts() {
+		loadList(this::loadAllBlogPosts, blogPosts::setValue);
+	}
+
+	@DatabaseExecutor
+	private ListUpdate loadAllBlogPosts(Transaction txn)
+			throws DbException {
+		long start = now();
+		List<BlogPostItem> posts = new ArrayList<>();
+		for (GroupId g : blogManager.getBlogIds(txn)) {
+			posts.addAll(loadBlogPosts(txn, g));
+		}
+		Collections.sort(posts);
+		logDuration(LOG, "Loading all posts", start);
+		return new ListUpdate(null, posts);
+	}
+
+	@UiThread
+	private void onBlogRemoved(GroupId g) {
+		List<BlogPostItem> items = removeListItems(getBlogPostItems(),
+				item -> item.getGroupId().equals(g)
+		);
+		if (items != null) {
+			blogPosts.setValue(new LiveResult<>(new ListUpdate(null, items)));
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/OnBlogPostClickListener.java

@@ -5,4 +5,6 @@ interface OnBlogPostClickListener {
 	void onBlogPostClick(BlogPostItem post);
 
 	void onAuthorClick(BlogPostItem post);
+
+	void onLinkClick(String url);
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogActivity.java

@@ -11,7 +11,7 @@ import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 
-import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
+import static org.briarproject.briar.android.blog.BlogPostFragment.POST_ID;
 
 public class ReblogActivity extends BriarActivity implements
 		BaseFragmentListener {
@@ -39,13 +39,11 @@ public class ReblogActivity extends BriarActivity implements
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		switch (item.getItemId()) {
-			case android.R.id.home:
-				onBackPressed();
-				return true;
-			default:
-				return super.onOptionsItemSelected(item);
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
 		}
+		return super.onOptionsItemSelected(item);
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogFragment.java

@@ -7,19 +7,17 @@ import android.view.ViewGroup;
 import android.widget.ProgressBar;
 import android.widget.ScrollView;
 
-import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.controller.handler.UiExceptionHandler;
-import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.android.widget.LinkDialogFragment;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
 
 import java.util.List;
@@ -27,13 +25,15 @@ import java.util.List;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import androidx.lifecycle.ViewModelProvider;
+
 import static android.view.View.FOCUS_DOWN;
 import static android.view.View.GONE;
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
-import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
+import static org.briarproject.briar.android.blog.BlogPostFragment.POST_ID;
 import static org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
@@ -42,12 +42,13 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 
 	public static final String TAG = ReblogFragment.class.getName();
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private BlogViewModel viewModel;
 	private ViewHolder ui;
 	private BlogPostItem item;
 
-	@Inject
-	FeedController feedController;
-
 	static ReblogFragment newInstance(GroupId groupId, MessageId messageId) {
 		ReblogFragment f = new ReblogFragment();
 
@@ -67,6 +68,8 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(BlogViewModel.class);
 	}
 
 	@Override
@@ -90,30 +93,20 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 		ui.input.setMaxTextLength(MAX_BLOG_POST_TEXT_LENGTH);
 		showProgressBar();
 
-		feedController.loadBlogPost(blogId, postId,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem result) {
-						item = result;
-						bindViewHolder();
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
+		viewModel.loadBlogPost(blogId, postId).observe(getViewLifecycleOwner(),
+				result -> result.onError(this::handleException)
+						.onSuccess(this::bindViewHolder)
+		);
 
 		return v;
 	}
 
-	private void bindViewHolder() {
-		if (item == null) return;
+	private void bindViewHolder(BlogPostItem item) {
+		this.item = item;
 
 		hideProgressBar();
 
-		ui.post.bindItem(item);
+		ui.post.bindItem(this.item);
 		ui.post.hideReblogButton();
 
 		ui.input.setReady(true);
@@ -124,13 +117,7 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	public void onSendClick(@Nullable String text,
 			List<AttachmentHeader> headers) {
 		ui.input.hideSoftKeyboard();
-		feedController.repeatPost(item, text,
-				new UiExceptionHandler<DbException>(this) {
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
+		viewModel.repeatPost(item, text);
 		finish();
 	}
 
@@ -144,7 +131,7 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 		ui.input.setVisibility(VISIBLE);
 	}
 
-	private class ViewHolder {
+	private class ViewHolder implements OnBlogPostClickListener {
 
 		private final ScrollView scrollView;
 		private final ProgressBar progressBar;
@@ -155,18 +142,25 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 			scrollView = v.findViewById(R.id.scrollView);
 			progressBar = v.findViewById(R.id.progressBar);
 			post = new BlogPostViewHolder(v.findViewById(R.id.postLayout),
-					true, new OnBlogPostClickListener() {
-				@Override
-				public void onBlogPostClick(BlogPostItem post) {
-					// do nothing
-				}
-
-				@Override
-				public void onAuthorClick(BlogPostItem post) {
-					// probably don't want to allow author clicks here
-				}
-			}, getFragmentManager());
+					true, this, false);
 			input = v.findViewById(R.id.inputText);
 		}
+
+		@Override
+		public void onBlogPostClick(BlogPostItem post) {
+			// do nothing
+		}
+
+		@Override
+		public void onAuthorClick(BlogPostItem post) {
+			// probably don't want to allow author clicks here
+		}
+
+		@Override
+		public void onLinkClick(String url) {
+			LinkDialogFragment f = LinkDialogFragment.newInstance(url);
+			f.show(getParentFragmentManager(), f.getUniqueTag());
+		}
 	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactsViewModel.java

@@ -151,7 +151,7 @@ public class ContactsViewModel extends DbViewModel implements EventListener {
 	@UiThread
 	private void updateItem(ContactId c,
 			Function<ContactListItem, ContactListItem> replacer, boolean sort) {
-		List<ContactListItem> list = updateListItems(contactListItems,
+		List<ContactListItem> list = updateListItems(getList(contactListItems),
 				itemToTest -> itemToTest.getContact().getId().equals(c),
 				replacer);
 		if (list == null) return;
@@ -161,10 +161,8 @@ public class ContactsViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void removeItem(ContactId c) {
-		List<ContactListItem> list = removeListItems(contactListItems,
+		removeAndUpdateListItems(contactListItems,
 				itemToTest -> itemToTest.getContact().getId().equals(c));
-		if (list == null) return;
-		contactListItems.setValue(new LiveResult<>(list));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/controller/SharingController.java

@@ -1,77 +0,0 @@
-package org.briarproject.briar.android.controller;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.Collection;
-
-import androidx.annotation.UiThread;
-
-@Deprecated
-@NotNullByDefault
-public interface SharingController {
-
-	/**
-	 * Sets the listener that is called when contacts go on or offline.
-	 */
-	@UiThread
-	void setSharingListener(SharingListener listener);
-
-	/**
-	 * Unsets the listener.
-	 */
-	@UiThread
-	void unsetSharingListener(SharingListener listener);
-
-	/**
-	 * Call this when your lifecycle starts,
-	 * so the listener will be called when information changes.
-	 */
-	@UiThread
-	void onStart();
-
-	/**
-	 * Call this when your lifecycle stops,
-	 * so that the controller knows it can stops listening to events.
-	 */
-	@UiThread
-	void onStop();
-
-	/**
-	 * Adds one contact to be tracked.
-	 */
-	@UiThread
-	void add(ContactId c);
-
-	/**
-	 * Adds a collection of contacts to be tracked.
-	 */
-	@UiThread
-	void addAll(Collection<ContactId> contacts);
-
-	/**
-	 * Call this when the contact identified by c is no longer sharing
-	 * the given group identified by GroupId g.
-	 */
-	@UiThread
-	void remove(ContactId c);
-
-	/**
-	 * Returns the number of online contacts.
-	 */
-	@UiThread
-	int getOnlineCount();
-
-	/**
-	 * Returns the total number of contacts that have been added.
-	 */
-	@UiThread
-	int getTotalCount();
-
-	interface SharingListener {
-
-		@UiThread
-		void onSharingInfoUpdated(int total, int online);
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/controller/SharingControllerImpl.java

@@ -1,109 +0,0 @@
-package org.briarproject.briar.android.controller;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
-
-import java.util.Collection;
-import java.util.HashSet;
-import java.util.Set;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.annotation.UiThread;
-
-@Deprecated
-@NotNullByDefault
-public class SharingControllerImpl implements SharingController, EventListener {
-
-	private final EventBus eventBus;
-	private final ConnectionRegistry connectionRegistry;
-
-	// UI thread
-	private final Set<ContactId> contacts = new HashSet<>();
-
-	// UI thread
-	@Nullable
-	private SharingListener listener;
-
-	@Inject
-	SharingControllerImpl(EventBus eventBus,
-			ConnectionRegistry connectionRegistry) {
-		this.eventBus = eventBus;
-		this.connectionRegistry = connectionRegistry;
-	}
-
-	@Override
-	public void setSharingListener(SharingListener listener) {
-		this.listener = listener;
-	}
-
-	@Override
-	public void unsetSharingListener(SharingListener listener) {
-		if (this.listener == listener) this.listener = null;
-	}
-
-	@Override
-	public void onStart() {
-		eventBus.addListener(this);
-	}
-
-	@Override
-	public void onStop() {
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof ContactConnectedEvent) {
-			setConnected(((ContactConnectedEvent) e).getContactId());
-		} else if (e instanceof ContactDisconnectedEvent) {
-			setConnected(((ContactDisconnectedEvent) e).getContactId());
-		}
-	}
-
-	@UiThread
-	private void setConnected(ContactId c) {
-		if (listener == null) throw new IllegalStateException();
-		if (contacts.contains(c)) {
-			int online = getOnlineCount();
-			listener.onSharingInfoUpdated(contacts.size(), online);
-		}
-	}
-
-	@Override
-	public void addAll(Collection<ContactId> c) {
-		contacts.addAll(c);
-	}
-
-	@Override
-	public void add(ContactId c) {
-		contacts.add(c);
-	}
-
-	@Override
-	public void remove(ContactId c) {
-		contacts.remove(c);
-	}
-
-	@Override
-	public int getOnlineCount() {
-		int online = 0;
-		for (ContactId c : contacts) {
-			if (connectionRegistry.isConnected(c)) online++;
-		}
-		return online;
-	}
-
-	@Override
-	public int getTotalCount() {
-		return contacts.size();
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListViewModel.java

@@ -145,7 +145,7 @@ class ForumListViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void onForumPostReceived(GroupId g, ForumPostHeader header) {
-		List<ForumListItem> list = updateListItems(forumItems,
+		List<ForumListItem> list = updateListItems(getList(forumItems),
 				itemToTest -> itemToTest.getForum().getId().equals(g),
 				itemToUpdate -> new ForumListItem(itemToUpdate, header));
 		if (list == null) return;
@@ -156,11 +156,9 @@ class ForumListViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void onGroupRemoved(GroupId groupId) {
-		List<ForumListItem> list = removeListItems(forumItems, i ->
+		removeAndUpdateListItems(forumItems, i ->
 				i.getForum().getId().equals(groupId)
 		);
-		if (list == null) return;
-		forumItems.setValue(new LiveResult<>(list));
 	}
 
 	void loadForumInvitations() {

briar-android/src/main/java/org/briarproject/briar/android/privategroup/list/GroupListViewModel.java

@@ -2,7 +2,6 @@ package org.briarproject.briar.android.privategroup.list;
 
 import android.app.Application;
 
-import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
@@ -173,7 +172,7 @@ class GroupListViewModel extends DbViewModel implements EventListener {
 	@UiThread
 	private void onGroupMessageAdded(GroupMessageHeader header) {
 		GroupId g = header.getGroupId();
-		List<GroupItem> list = updateListItems(groupItems,
+		List<GroupItem> list = updateListItems(getList(groupItems),
 				itemToTest -> itemToTest.getId().equals(g),
 				itemToUpdate -> new GroupItem(itemToUpdate, header));
 		if (list == null) return;
@@ -184,7 +183,7 @@ class GroupListViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void onGroupDissolved(GroupId groupId) {
-		List<GroupItem> list = updateListItems(groupItems,
+		List<GroupItem> list = updateListItems(getList(groupItems),
 				itemToTest -> itemToTest.getId().equals(groupId),
 				itemToUpdate -> new GroupItem(itemToUpdate, true));
 		if (list == null) return;
@@ -193,10 +192,7 @@ class GroupListViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void onGroupRemoved(GroupId groupId) {
-		List<GroupItem> list =
-				removeListItems(groupItems, i -> i.getId().equals(groupId));
-		if (list == null) return;
-		groupItems.setValue(new LiveResult<>(list));
+		removeAndUpdateListItems(groupItems, i -> i.getId().equals(groupId));
 	}
 
 	void removeGroup(GroupId g) {

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -34,7 +34,6 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.reporting.FeedbackActivity;
 import org.briarproject.briar.android.view.ArticleMovementMethod;
-import org.briarproject.briar.android.widget.LinkDialogFragment;
 
 import java.util.Locale;
 
@@ -49,8 +48,8 @@ import androidx.appcompat.app.AlertDialog;
 import androidx.core.content.ContextCompat;
 import androidx.core.hardware.fingerprint.FingerprintManagerCompat;
 import androidx.core.text.HtmlCompat;
+import androidx.core.util.Consumer;
 import androidx.fragment.app.FragmentActivity;
-import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
@@ -198,8 +197,7 @@ public class UiUtils {
 	}
 
 	public static void makeLinksClickable(TextView v,
-			@Nullable FragmentManager fm) {
-		if (fm == null) return;
+			Consumer<String> onLinkClicked) {
 		SpannableStringBuilder ssb = new SpannableStringBuilder(v.getText());
 		URLSpan[] spans = ssb.getSpans(0, ssb.length(), URLSpan.class);
 		for (URLSpan span : spans) {
@@ -210,8 +208,7 @@ public class UiUtils {
 			ClickableSpan cSpan = new ClickableSpan() {
 				@Override
 				public void onClick(View v2) {
-					LinkDialogFragment f = LinkDialogFragment.newInstance(url);
-					f.show(fm, f.getUniqueTag());
+					onLinkClicked.accept(url);
 				}
 			};
 			ssb.setSpan(cSpan, start, end, 0);

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/DbViewModel.java

@@ -1,6 +1,7 @@
 package org.briarproject.briar.android.viewmodel;
 
 import android.app.Application;
+import android.widget.Toast;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbCallable;
@@ -11,8 +12,10 @@ import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.concurrent.Executor;
@@ -20,6 +23,7 @@ import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
 
+import androidx.annotation.AnyThread;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
@@ -27,8 +31,10 @@ import androidx.arch.core.util.Function;
 import androidx.core.util.Consumer;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 import androidx.recyclerview.widget.RecyclerView;
 
+import static android.widget.Toast.LENGTH_LONG;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -114,9 +120,11 @@ public abstract class DbViewModel extends AndroidViewModel {
 	 * This method ensures that those operations can be processed on the
 	 * UiThread in the correct order so that the removed message will not be
 	 * re-added when the re-load completes.
+	 *
+	 * TODO: Rename this method and update javadoc, as it's not restricted to
+	 *  lists
 	 */
-	protected <T extends List<?>> void loadList(
-			DbCallable<T, DbException> task,
+	protected <T> void loadList(DbCallable<T, DbException> task,
 			UiConsumer<LiveResult<T>> uiConsumer) {
 		dbExecutor.execute(() -> {
 			try {
@@ -143,25 +151,46 @@ public abstract class DbViewModel extends AndroidViewModel {
 	}
 
 	/**
-	 * Creates a copy of the list available in the given LiveData
-	 * and replaces items where the given test function returns true.
+	 * Creates a copy of the given list and adds the given item to the copy.
 	 *
-	 * @return a copy of the list in the LiveData with item(s) replaced
-	 * or null when the
-	 * <ul>
-	 * <li> LiveData does not have a value
-	 * <li> LiveResult in the LiveData has an error
-	 * <li> test function did return false for all items in the list
-	 * </ul>
+	 * @return an updated copy of the list, or null if the list is null
 	 */
 	@Nullable
-	protected <T> List<T> updateListItems(
-			LiveData<LiveResult<List<T>>> liveData, Function<T, Boolean> test,
-			Function<T, T> replacer) {
-		List<T> items = getListCopy(liveData);
-		if (items == null) return null;
+	protected <T> List<T> addListItem(@Nullable List<T> list, T item) {
+		if (list == null) return null;
+		List<T> copy = new ArrayList<>(list);
+		copy.add(item);
+		return copy;
+	}
 
-		ListIterator<T> iterator = items.listIterator();
+	/**
+	 * Creates a copy of the given list and adds the given items to the copy.
+	 *
+	 * @return an updated copy of the list, or null if the list is null
+	 */
+	@Nullable
+	protected <T> List<T> addListItems(@Nullable List<T> list,
+			Collection<T> items) {
+		if (list == null) return null;
+		List<T> copy = new ArrayList<>(list);
+		copy.addAll(items);
+		return copy;
+	}
+
+	/**
+	 * Creates a copy of the given list, replacing items where the given test
+	 * function returns true.
+	 *
+	 * @return an updated copy of the list, or null if either the list is null
+	 * or the test function returns false for all items
+	 */
+	@Nullable
+	protected <T> List<T> updateListItems(@Nullable List<T> list,
+			Function<T, Boolean> test, Function<T, T> replacer) {
+		if (list == null) return null;
+		List<T> copy = new ArrayList<>(list);
+
+		ListIterator<T> iterator = copy.listIterator();
 		boolean changed = false;
 		while (iterator.hasNext()) {
 			T item = iterator.next();
@@ -170,28 +199,23 @@ public abstract class DbViewModel extends AndroidViewModel {
 				iterator.set(replacer.apply(item));
 			}
 		}
-		return changed ? items : null;
+		return changed ? copy : null;
 	}
 
 	/**
-	 * Creates a copy of the list available in the given LiveData
-	 * and removes the items from it where the given test function returns true.
+	 * Creates a copy of the given list, removing items from it where the given
+	 * test function returns true.
 	 *
-	 * @return a copy of the list in the LiveData with item(s) removed
-	 * or null when the
-	 * <ul>
-	 * <li> LiveData does not have a value
-	 * <li> LiveResult in the LiveData has an error
-	 * <li> test function did return false for all items in the list
-	 * </ul>
+	 * @return an updated copy of the list, or null if either the list is null
+	 * or the test function returns false for all items
 	 */
 	@Nullable
-	protected <T> List<T> removeListItems(
-			LiveData<LiveResult<List<T>>> liveData, Function<T, Boolean> test) {
-		List<T> items = getListCopy(liveData);
-		if (items == null) return null;
+	protected <T> List<T> removeListItems(@Nullable List<T> list,
+			Function<T, Boolean> test) {
+		if (list == null) return null;
+		List<T> copy = new ArrayList<>(list);
 
-		ListIterator<T> iterator = items.listIterator();
+		ListIterator<T> iterator = copy.listIterator();
 		boolean changed = false;
 		while (iterator.hasNext()) {
 			T item = iterator.next();
@@ -200,21 +224,58 @@ public abstract class DbViewModel extends AndroidViewModel {
 				iterator.remove();
 			}
 		}
-		return changed ? items : null;
+		return changed ? copy : null;
 	}
 
 	/**
-	 * Retrieves a copy of the list of items from the given LiveData
-	 * or null if it is not available.
-	 * The list copy can be safely mutated.
+	 * Updates the given LiveData with a copy of its list
+	 * with the items removed where the given test function returns true.
+	 * <p>
+	 * Nothing is updated, if the
+	 * <ul>
+	 * <li> LiveData does not have a value
+	 * <li> LiveResult in the LiveData has an error
+	 * <li> test function returned false for all items in the list
+	 * </ul>
+	 */
+	@UiThread
+	protected <T> void removeAndUpdateListItems(
+			MutableLiveData<LiveResult<List<T>>> liveData,
+			Function<T, Boolean> test) {
+		List<T> copy = removeListItems(getList(liveData), test);
+		if (copy != null) liveData.setValue(new LiveResult<>(copy));
+	}
+
+	/**
+	 * Returns the list of items from the given LiveData, or null if no list is
+	 * available.
 	 */
 	@Nullable
-	private <T> List<T> getListCopy(LiveData<LiveResult<List<T>>> liveData) {
+	protected <T> List<T> getList(LiveData<LiveResult<List<T>>> liveData) {
 		LiveResult<List<T>> value = liveData.getValue();
 		if (value == null) return null;
-		List<T> list = value.getResultOrNull();
-		if (list == null) return null;
-		return new ArrayList<>(list);
+		return value.getResultOrNull();
+	}
+
+	/**
+	 * Logs the exception and shows a Toast to the user.
+	 * <p>
+	 * Errors that are likely or expected to happen should not use this method
+	 * and show proper error states in UI.
+	 */
+	@AnyThread
+	protected void handleException(Exception e) {
+		logException(LOG, WARNING, e);
+		androidExecutor.runOnUiThread(() -> {
+			String msg = "Error: " + e.getClass().getSimpleName();
+			if (!StringUtils.isNullOrEmpty(e.getMessage())) {
+				msg += " " + e.getMessage();
+			}
+			if (e.getCause() != null) {
+				msg += " caused by " + e.getCause().getClass().getSimpleName();
+			}
+			Toast.makeText(getApplication(), msg, LENGTH_LONG).show();
+		});
 	}
 
 }

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogManager.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 
 import java.util.Collection;
+import java.util.List;
 
 import javax.annotation.Nullable;
 
@@ -98,21 +99,38 @@ public interface BlogManager {
 	 */
 	Collection<Blog> getBlogs() throws DbException;
 
+	/**
+	 * Returns the group IDs of all blogs to which the user subscribes.
+	 */
+	Collection<GroupId> getBlogIds(Transaction txn) throws DbException;
+
 	/**
 	 * Returns the header of the blog post with the given ID.
 	 */
-	BlogPostHeader getPostHeader(GroupId g, MessageId m) throws DbException;
+	BlogPostHeader getPostHeader(Transaction txn, GroupId g, MessageId m)
+			throws DbException;
 
 	/**
 	 * Returns the text of the blog post with the given ID.
 	 */
 	String getPostText(MessageId m) throws DbException;
 
+	/**
+	 * Returns the text of the blog post with the given ID.
+	 */
+	String getPostText(Transaction txn, MessageId m) throws DbException;
+
 	/**
 	 * Returns the headers of all posts in the given blog.
 	 */
 	Collection<BlogPostHeader> getPostHeaders(GroupId g) throws DbException;
 
+	/**
+	 * Returns the headers of all posts in the given blog.
+	 */
+	List<BlogPostHeader> getPostHeaders(Transaction txn, GroupId g)
+			throws DbException;
+
 	/**
 	 * Marks a blog post as read or unread.
 	 */

briar-core/src/main/java/org/briarproject/briar/blog/BlogManagerImpl.java

@@ -446,19 +446,22 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 	}
 
 	@Override
-	public BlogPostHeader getPostHeader(GroupId g, MessageId m)
+	public Collection<GroupId> getBlogIds(Transaction txn) throws DbException {
+		List<GroupId> groupIds = new ArrayList<>();
+		Collection<Group> groups = db.getGroups(txn, CLIENT_ID, MAJOR_VERSION);
+		for (Group g : groups) groupIds.add(g.getId());
+		return groupIds;
+	}
+
+	@Override
+	public BlogPostHeader getPostHeader(Transaction txn, GroupId g, MessageId m)
 			throws DbException {
-		Transaction txn = db.startTransaction(true);
 		try {
 			BdfDictionary meta =
 					clientHelper.getMessageMetadataAsDictionary(txn, m);
-			BlogPostHeader h = getPostHeaderFromMetadata(txn, g, m, meta);
-			db.commitTransaction(txn);
-			return h;
+			return getPostHeaderFromMetadata(txn, g, m, meta);
 		} catch (FormatException e) {
 			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
 		}
 	}
 
@@ -471,6 +474,15 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 		}
 	}
 
+	@Override
+	public String getPostText(Transaction txn, MessageId m) throws DbException {
+		try {
+			return getPostText(clientHelper.getMessageAsList(txn, m));
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
 	private String getPostText(BdfList message) throws FormatException {
 		MessageType type = MessageType.valueOf(message.getLong(0).intValue());
 		if (type == POST) {
@@ -488,7 +500,12 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 	@Override
 	public Collection<BlogPostHeader> getPostHeaders(GroupId g)
 			throws DbException {
+		return db.transactionWithResult(true, txn -> getPostHeaders(txn, g));
+	}
 
+	@Override
+	public List<BlogPostHeader> getPostHeaders(Transaction txn, GroupId g)
+			throws DbException {
 		// Query for posts and comments only
 		BdfDictionary query1 = BdfDictionary.of(
 				new BdfEntry(KEY_TYPE, POST.getInt())
@@ -497,8 +514,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 				new BdfEntry(KEY_TYPE, COMMENT.getInt())
 		);
 
-		Collection<BlogPostHeader> headers = new ArrayList<>();
-		Transaction txn = db.startTransaction(true);
+		List<BlogPostHeader> headers = new ArrayList<>();
 		try {
 			Map<MessageId, BdfDictionary> metadata1 =
 					clientHelper.getMessageMetadataAsDictionary(txn, g, query1);
@@ -528,13 +544,10 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 						entry.getKey(), meta, authorInfos);
 				headers.add(h);
 			}
-			db.commitTransaction(txn);
-			return headers;
 		} catch (FormatException e) {
 			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
 		}
+		return headers;
 	}
 
 	@Override

briar-headless/src/main/java/org/briarproject/briar/headless/blogs/BlogControllerImpl.kt

@@ -3,12 +3,15 @@ package org.briarproject.briar.headless.blogs
 import com.fasterxml.jackson.databind.ObjectMapper
 import io.javalin.http.BadRequestResponse
 import io.javalin.http.Context
+import org.briarproject.bramble.api.db.DbException
+import org.briarproject.bramble.api.db.TransactionManager
 import org.briarproject.bramble.api.identity.IdentityManager
 import org.briarproject.bramble.api.system.Clock
 import org.briarproject.bramble.util.StringUtils.utf8IsTooLong
 import org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH
 import org.briarproject.briar.api.blog.BlogManager
 import org.briarproject.briar.api.blog.BlogPostFactory
+import org.briarproject.briar.api.blog.BlogPostHeader
 import org.briarproject.briar.headless.getFromJson
 import javax.annotation.concurrent.Immutable
 import javax.inject.Inject
@@ -21,6 +24,7 @@ internal class BlogControllerImpl
 constructor(
     private val blogManager: BlogManager,
     private val blogPostFactory: BlogPostFactory,
+    private val db: TransactionManager,
     private val identityManager: IdentityManager,
     private val objectMapper: ObjectMapper,
     private val clock: Clock
@@ -45,8 +49,10 @@ constructor(
         val blog = blogManager.getPersonalBlog(author)
         val now = clock.currentTimeMillis()
         val post = blogPostFactory.createBlogPost(blog.id, now, null, author, text)
-        blogManager.addLocalPost(post)
-        val header = blogManager.getPostHeader(blog.id, post.message.id)
+        val header = db.transactionWithResult<BlogPostHeader, DbException>(true) { txn ->
+            blogManager.addLocalPost(txn, post)
+            return@transactionWithResult blogManager.getPostHeader(txn, blog.id, post.message.id)
+        }
         return ctx.json(header.output(text))
     }
 

briar-headless/src/test/java/org/briarproject/briar/headless/ControllerTest.kt

@@ -7,6 +7,7 @@ import io.mockk.mockk
 import org.briarproject.bramble.api.connection.ConnectionRegistry
 import org.briarproject.bramble.api.contact.Contact
 import org.briarproject.bramble.api.contact.ContactManager
+import org.briarproject.bramble.api.db.TransactionManager
 import org.briarproject.bramble.api.identity.Author
 import org.briarproject.bramble.api.identity.IdentityManager
 import org.briarproject.bramble.api.identity.LocalAuthor
@@ -24,6 +25,7 @@ import javax.servlet.http.HttpServletResponse
 
 abstract class ControllerTest {
 
+    protected val db = mockk<TransactionManager>()
     protected val contactManager = mockk<ContactManager>()
     protected val conversationManager = mockk<ConversationManager>()
     protected val identityManager = mockk<IdentityManager>()

briar-headless/src/test/java/org/briarproject/briar/headless/blogs/BlogControllerTest.kt

@@ -6,14 +6,22 @@ import io.mockk.Runs
 import io.mockk.every
 import io.mockk.just
 import io.mockk.mockk
-import org.briarproject.briar.api.identity.AuthorInfo
-import org.briarproject.briar.api.identity.AuthorInfo.Status.OURSELVES
+import io.mockk.slot
+import org.briarproject.bramble.api.db.DbCallable
+import org.briarproject.bramble.api.db.DbException
+import org.briarproject.bramble.api.db.Transaction
 import org.briarproject.bramble.api.sync.MessageId
 import org.briarproject.bramble.identity.output
 import org.briarproject.bramble.util.StringUtils.getRandomString
-import org.briarproject.briar.api.blog.*
+import org.briarproject.briar.api.blog.Blog
 import org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH
+import org.briarproject.briar.api.blog.BlogManager
+import org.briarproject.briar.api.blog.BlogPost
+import org.briarproject.briar.api.blog.BlogPostFactory
+import org.briarproject.briar.api.blog.BlogPostHeader
 import org.briarproject.briar.api.blog.MessageType.POST
+import org.briarproject.briar.api.identity.AuthorInfo
+import org.briarproject.briar.api.identity.AuthorInfo.Status.OURSELVES
 import org.briarproject.briar.headless.ControllerTest
 import org.junit.jupiter.api.Assertions.assertThrows
 import org.junit.jupiter.api.Test
@@ -24,7 +32,7 @@ internal class BlogControllerTest : ControllerTest() {
     private val blogPostFactory = mockk<BlogPostFactory>()
 
     private val controller =
-        BlogControllerImpl(blogManager, blogPostFactory, identityManager, objectMapper, clock)
+        BlogControllerImpl(blogManager, blogPostFactory, db, identityManager, objectMapper, clock)
 
     private val blog = Blog(group, author, false)
     private val parentId: MessageId? = null
@@ -46,6 +54,8 @@ internal class BlogControllerTest : ControllerTest() {
     @Test
     fun testCreate() {
         val post = BlogPost(message, null, localAuthor)
+        val dbSlot = slot<DbCallable<BlogPostHeader, DbException>>()
+        val txn = Transaction(Object(), true)
 
         every { ctx.body() } returns """{"text": "$text"}"""
         every { identityManager.localAuthor } returns localAuthor
@@ -60,8 +70,13 @@ internal class BlogControllerTest : ControllerTest() {
                 text
             )
         } returns post
-        every { blogManager.addLocalPost(post) } just Runs
-        every { blogManager.getPostHeader(post.message.groupId, post.message.id) } returns header
+        every { db.transactionWithResult(true, capture(dbSlot)) } answers {
+            dbSlot.captured.call(txn)
+        }
+        every { blogManager.addLocalPost(txn, post) } just Runs
+        every {
+            blogManager.getPostHeader(txn, post.message.groupId, post.message.id)
+        } returns header
         every { ctx.json(header.output(text)) } returns ctx
 
         controller.createPost(ctx)