Merge branch '705-blog-pager-race-conditions' into 'master'

Remove blog pagers

I set out to fix potential race conditions in the blog pagers (the screens you reach by tapping the body of a blog post, that allow you to swipe left and right through the posts in the combined feed or a single blog). The race conditions here are similar to those addressed by !356, but the adapters don't inherit from BriarAdapter so they need to be fixed separately.

While I was looking into this I found a few minor problems with the pagers:
* The feed pager wasn't responding to events - this was fixed in !398
* The feed pager finishes NavDrawerActivity when any blog is removed
* The feed isn't updated when a blog is added (this applies to the list view as well as the pager)
* Posts aren't removed from the feed pager when a blog is removed

The last problem is quite serious - the feed pager's adapter contains posts that are no longer in the DB, so they'll fail to load. To fix that problem, the adapter needs to be cleared in onStop() and repopulated in onStart(). This is the same approach we use for other adapters where items can be removed from the underlying dataset. Unfortunately, FragmentStatePagerAdapter has some odd behaviour when you clear and repopulate it:

1. When reselecting the previously selected item after clearing and repopulating the adapter, the item slides into view instead of just appearing, which makes it look like you've accidentally swiped.
2. Items are sometimes duplicated when clearing and repopulating the adapter, so swiping left or right shows another copy of the same post.

These problems only seem to happen if the adapter is cleared - adding new posts works fine on master, although I think there might be some luck involved - FragmentStatePagerAdapter doesn't seem to be designed to support items changing positions.

I spent a lot of time trying to resolve these problems before concluding that maybe it wasn't worth it, and we should just remove the pagers. That's what's currently implemented in this branch. Tapping the body of a post will show the full-length post, but you won't be able to swipe left or right.

The swiping functionality was nice to have, so if you have ideas for fixing the bugs I'd love to hear them. But I'd rather remove this functionality than keep it in a buggy state with no plan for how to fix it.

Closes #705

See merge request !400

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

@@ -6,10 +6,8 @@ import org.briarproject.android.blogs.BlogActivity;
 import org.briarproject.android.blogs.BlogFragment;
 import org.briarproject.android.blogs.BlogModule;
 import org.briarproject.android.blogs.BlogPostFragment;
-import org.briarproject.android.blogs.BlogPostPagerFragment;
 import org.briarproject.android.blogs.FeedFragment;
 import org.briarproject.android.blogs.FeedPostFragment;
-import org.briarproject.android.blogs.FeedPostPagerFragment;
 import org.briarproject.android.blogs.ReblogActivity;
 import org.briarproject.android.blogs.ReblogFragment;
 import org.briarproject.android.blogs.RssFeedImportActivity;
@@ -132,10 +130,6 @@ public interface ActivityComponent {
 
 	void inject(FeedPostFragment fragment);
 
-	void inject(BlogPostPagerFragment fragment);
-
-	void inject(FeedPostPagerFragment fragment);
-
 	void inject(ReblogFragment fragment);
 
 	void inject(ReblogActivity activity);

briar-android/src/org/briarproject/android/blogs/BaseController.java

@@ -8,6 +8,7 @@ import org.briarproject.android.controller.handler.ExceptionHandler;
 import org.briarproject.android.controller.handler.ResultExceptionHandler;
 import org.briarproject.api.blogs.BlogPostHeader;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.NotNullByDefault;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.MessageId;
 
@@ -33,9 +34,10 @@ interface BaseController {
 	void repeatPost(BlogPostItem item, @Nullable String comment,
 			ExceptionHandler<DbException> handler);
 
-	void setOnBlogPostAddedListener(OnBlogPostAddedListener listener);
+	void setBlogListener(BlogListener listener);
 
-	interface OnBlogPostAddedListener extends DestroyableContext {
+	@NotNullByDefault
+	interface BlogListener extends DestroyableContext {
 
 		@UiThread
 		void onBlogPostAdded(BlogPostHeader header, boolean local);

briar-android/src/org/briarproject/android/blogs/BaseControllerImpl.java

@@ -46,7 +46,7 @@ abstract class BaseControllerImpl extends DbControllerImpl
 	private final Map<MessageId, BlogPostHeader> headerCache =
 			new ConcurrentHashMap<>();
 
-	private volatile OnBlogPostAddedListener listener;
+	private volatile BlogListener listener;
 
 	BaseControllerImpl(@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager, EventBus eventBus,
@@ -73,7 +73,7 @@ abstract class BaseControllerImpl extends DbControllerImpl
 	}
 
 	@Override
-	public void setOnBlogPostAddedListener(OnBlogPostAddedListener listener) {
+	public void setBlogListener(BlogListener listener) {
 		this.listener = listener;
 	}
 

briar-android/src/org/briarproject/android/blogs/BasePostFragment.java

@@ -11,7 +11,8 @@ import android.widget.ProgressBar;
 
 import org.briarproject.R;
 import org.briarproject.android.fragment.BaseFragment;
-import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.api.nullsafety.ParametersNotNullByDefault;
 
 import java.util.logging.Logger;
 
@@ -19,8 +20,13 @@ import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.android.util.AndroidUtils.MIN_RESOLUTION;
 
+@UiThread
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 abstract class BasePostFragment extends BaseFragment {
 
+	static final String POST_ID = "briar.POST_ID";
+
 	private static final Logger LOG =
 			Logger.getLogger(BasePostFragment.class.getName());
 
@@ -33,8 +39,9 @@ abstract class BasePostFragment extends BaseFragment {
 	@CallSuper
 	@Nullable
 	@Override
-	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+	public View onCreateView(LayoutInflater inflater,
-			Bundle savedInstanceState) {
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
 		view = inflater.inflate(R.layout.fragment_blog_post, container,
 				false);
 		progressBar = (ProgressBar) view.findViewById(R.id.progressBar);
@@ -64,12 +71,6 @@ abstract class BasePostFragment extends BaseFragment {
 		ui.bindItem(post);
 	}
 
-	@UiThread
-	protected void onBlogPostLoadException(DbException exception) {
-		// TODO: Decide how to handle errors in the UI
-		finish();
-	}
-
 	private void startPeriodicUpdate() {
 		refresher = new Runnable() {
 			@Override

briar-android/src/org/briarproject/android/blogs/BasePostPagerFragment.java

@@ -1,183 +0,0 @@
-package org.briarproject.android.blogs;
-
-import android.os.Bundle;
-import android.support.annotation.Nullable;
-import android.support.annotation.UiThread;
-import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentStatePagerAdapter;
-import android.support.v4.view.ViewPager;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ProgressBar;
-
-import org.briarproject.R;
-import org.briarproject.android.blogs.BaseController.OnBlogPostAddedListener;
-import org.briarproject.android.fragment.BaseFragment;
-import org.briarproject.api.blogs.BlogPostHeader;
-import org.briarproject.api.db.DbException;
-import org.briarproject.api.sync.MessageId;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-
-import static android.view.View.INVISIBLE;
-import static android.view.View.VISIBLE;
-import static org.briarproject.android.blogs.BasePostPagerFragment.BlogPostPagerAdapter.INVALID_POSITION;
-
-abstract class BasePostPagerFragment extends BaseFragment
-		implements OnBlogPostAddedListener {
-
-	static final String POST_ID = "briar.POST_ID";
-
-	private ViewPager pager;
-	private ProgressBar progressBar;
-	private BlogPostPagerAdapter postPagerAdapter;
-	private MessageId postId;
-
-	@Nullable
-	@Override
-	public View onCreateView(LayoutInflater inflater, ViewGroup container,
-			Bundle state) {
-
-		Bundle args;
-		if (state == null) args = getArguments();
-		else args = state;
-		byte[] p = args.getByteArray(POST_ID);
-		if (p == null)
-			throw new IllegalStateException("No post ID in args");
-		postId = new MessageId(p);
-
-		View v = inflater.inflate(R.layout.fragment_blog_post_pager, container,
-				false);
-		progressBar = (ProgressBar) v.findViewById(R.id.progressBar);
-		progressBar.setVisibility(VISIBLE);
-
-		pager = (ViewPager) v.findViewById(R.id.pager);
-		postPagerAdapter = new BlogPostPagerAdapter(getChildFragmentManager());
-
-		return v;
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		if (postId == null) {
-			MessageId selected = getSelectedPost();
-			if (selected != null) loadBlogPosts(selected);
-		} else {
-			loadBlogPosts(postId);
-		}
-	}
-
-	@Override
-	public void onSaveInstanceState(Bundle outState) {
-		super.onSaveInstanceState(outState);
-		MessageId selected = getSelectedPost();
-		if (selected != null)
-			outState.putByteArray(POST_ID, selected.getBytes());
-	}
-
-	@Override
-	public void onBlogPostAdded(BlogPostHeader header, boolean local) {
-		loadBlogPost(header);
-	}
-
-	abstract void loadBlogPosts(final MessageId select);
-
-	abstract void loadBlogPost(BlogPostHeader header);
-
-	@UiThread
-	protected void onBlogPostsLoaded(MessageId select,
-			Collection<BlogPostItem> posts) {
-
-		postId = null;
-		postPagerAdapter.setPosts(posts);
-		selectPost(select);
-	}
-
-	@UiThread
-	protected void onBlogPostsLoadedException(DbException exception) {
-		// TODO: Decide how to handle errors in the UI
-		finish();
-	}
-
-	@Nullable
-	private MessageId getSelectedPost() {
-		if (postPagerAdapter.getCount() == 0) return null;
-		int position = pager.getCurrentItem();
-		return postPagerAdapter.getPost(position).getId();
-	}
-
-	private void selectPost(MessageId m) {
-		int pos = postPagerAdapter.getPostPosition(m);
-		if (pos != INVALID_POSITION) {
-			progressBar.setVisibility(INVISIBLE);
-			pager.setAdapter(postPagerAdapter);
-			pager.setCurrentItem(pos);
-		}
-	}
-
-	protected void addPost(BlogPostItem post) {
-		MessageId selected = getSelectedPost();
-		postPagerAdapter.addPost(post);
-		if (selected != null) selectPost(selected);
-	}
-
-	@UiThread
-	static class BlogPostPagerAdapter extends FragmentStatePagerAdapter {
-
-		static final int INVALID_POSITION = -1;
-		private final List<BlogPostItem> posts = new ArrayList<>();
-
-		private BlogPostPagerAdapter(FragmentManager fm) {
-			super(fm);
-		}
-
-		@Override
-		public int getCount() {
-			return posts.size();
-		}
-
-		@Override
-		public Fragment getItem(int position) {
-			BlogPostItem post = posts.get(position);
-			return FeedPostFragment.newInstance(post.getGroupId(), post.getId());
-		}
-
-		private BlogPostItem getPost(int position) {
-			return posts.get(position);
-		}
-
-		private void setPosts(Collection<BlogPostItem> posts) {
-			this.posts.clear();
-			this.posts.addAll(posts);
-			Collections.sort(this.posts);
-			notifyDataSetChanged();
-		}
-
-		private void addPost(BlogPostItem post) {
-			posts.add(post);
-			Collections.sort(posts);
-			notifyDataSetChanged();
-		}
-
-		private int getPostPosition(MessageId m) {
-			int count = getCount();
-			for (int i = 0; i < count; i++) {
-				if (getPost(i).getId().equals(m)) {
-					return i;
-				}
-			}
-			return INVALID_POSITION;
-		}
-	}
-
-	@Override
-	public void onBlogRemoved() {
-		finish();
-	}
-}

briar-android/src/org/briarproject/android/blogs/BlogActivity.java

@@ -49,7 +49,7 @@ public class BlogActivity extends BriarActivity implements
 
 	@Override
 	public void onBlogPostClick(BlogPostItem post) {
-		BlogPostPagerFragment f = BlogPostPagerFragment.newInstance(post.getId());
+		BlogPostFragment f = BlogPostFragment.newInstance(post.getId());
 		getSupportFragmentManager().beginTransaction()
 				.replace(R.id.fragmentContainer, f, f.getUniqueTag())
 				.addToBackStack(f.getUniqueTag())

briar-android/src/org/briarproject/android/blogs/BlogFragment.java

@@ -4,6 +4,7 @@ import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
 import android.support.design.widget.Snackbar;
 import android.support.v4.app.ActivityOptionsCompat;
 import android.support.v4.content.ContextCompat;
@@ -19,7 +20,7 @@ import android.widget.Toast;
 
 import org.briarproject.R;
 import org.briarproject.android.ActivityComponent;
-import org.briarproject.android.blogs.BaseController.OnBlogPostAddedListener;
+import org.briarproject.android.blogs.BaseController.BlogListener;
 import org.briarproject.android.blogs.BlogPostAdapter.OnBlogPostClickListener;
 import org.briarproject.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.android.fragment.BaseFragment;
@@ -46,10 +47,11 @@ import static org.briarproject.android.BriarActivity.GROUP_ID;
 import static org.briarproject.android.blogs.BlogActivity.REQUEST_SHARE;
 import static org.briarproject.android.blogs.BlogActivity.REQUEST_WRITE_POST;
 
+@UiThread
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class BlogFragment extends BaseFragment implements
-		OnBlogPostAddedListener {
+		BlogListener {
 
 	private final static String TAG = BlogFragment.class.getName();
 
@@ -99,7 +101,7 @@ public class BlogFragment extends BaseFragment implements
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
-		blogController.setOnBlogPostAddedListener(this);
+		blogController.setBlogListener(this);
 	}
 
 	@Override

briar-android/src/org/briarproject/android/blogs/BlogPostFragment.java

@@ -2,6 +2,7 @@ package org.briarproject.android.blogs;
 
 import android.os.Bundle;
 import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -9,15 +10,18 @@ import android.view.ViewGroup;
 import org.briarproject.android.ActivityComponent;
 import org.briarproject.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.api.sync.MessageId;
 
 import javax.inject.Inject;
 
-import static org.briarproject.android.blogs.BasePostPagerFragment.POST_ID;
+@UiThread
-
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class BlogPostFragment extends BasePostFragment {
 
-	public final static String TAG = BlogPostFragment.class.getName();
+	private static final String TAG = BlogPostFragment.class.getName();
 
 	private MessageId postId;
 
@@ -36,8 +40,9 @@ public class BlogPostFragment extends BasePostFragment {
 
 	@Nullable
 	@Override
-	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+	public View onCreateView(LayoutInflater inflater,
-			Bundle savedInstanceState) {
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
 
 		Bundle args = getArguments();
 		byte[] p = args.getByteArray(POST_ID);
@@ -67,9 +72,11 @@ public class BlogPostFragment extends BasePostFragment {
 					public void onResultUi(BlogPostItem post) {
 						onBlogPostLoaded(post);
 					}
+
 					@Override
 					public void onExceptionUi(DbException exception) {
-						onBlogPostLoadException(exception);
+						// TODO: Decide how to handle errors in the UI
+						finish();
 					}
 				});
 	}

briar-android/src/org/briarproject/android/blogs/BlogPostItem.java

@@ -9,7 +9,9 @@ import org.briarproject.api.identity.Author.Status;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.MessageId;
 
-// This class is not thread-safe
+import javax.annotation.concurrent.NotThreadSafe;
+
+@NotThreadSafe
 public class BlogPostItem implements Comparable<BlogPostItem> {
 
 	private final BlogPostHeader header;

briar-android/src/org/briarproject/android/blogs/BlogPostPagerFragment.java

@@ -1,78 +0,0 @@
-package org.briarproject.android.blogs;
-
-import android.os.Bundle;
-
-import org.briarproject.android.ActivityComponent;
-import org.briarproject.android.controller.handler.UiResultExceptionHandler;
-import org.briarproject.api.blogs.BlogPostHeader;
-import org.briarproject.api.db.DbException;
-import org.briarproject.api.sync.MessageId;
-
-import java.util.Collection;
-
-import javax.inject.Inject;
-
-public class BlogPostPagerFragment extends BasePostPagerFragment {
-
-	public final static String TAG = BlogPostPagerFragment.class.getName();
-
-	@Inject
-	BlogController blogController;
-
-	static BlogPostPagerFragment newInstance(MessageId postId) {
-		BlogPostPagerFragment f = new BlogPostPagerFragment();
-
-		Bundle args = new Bundle();
-		args.putByteArray(POST_ID, postId.getBytes());
-		f.setArguments(args);
-
-		return f;
-	}
-
-	@Override
-	public void injectFragment(ActivityComponent component) {
-		component.inject(this);
-		blogController.setOnBlogPostAddedListener(this);
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
-
-	@Override
-	void loadBlogPosts(final MessageId select) {
-		blogController.loadBlogPosts(
-				new UiResultExceptionHandler<Collection<BlogPostItem>, DbException>(
-						this) {
-					@Override
-					public void onResultUi(Collection<BlogPostItem> posts) {
-						onBlogPostsLoaded(select, posts);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						onBlogPostsLoadedException(exception);
-					}
-				});
-	}
-
-	@Override
-	void loadBlogPost(BlogPostHeader header) {
-		blogController.loadBlogPost(header,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						addPost(post);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						// TODO: Decide how to handle errors in the UI
-						finish();
-					}
-				});
-	}
-}

briar-android/src/org/briarproject/android/blogs/BlogPostViewHolder.java

@@ -30,7 +30,7 @@ import static android.support.v4.app.ActivityOptionsCompat.makeSceneTransitionAn
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.android.BriarActivity.GROUP_ID;
-import static org.briarproject.android.blogs.BasePostPagerFragment.POST_ID;
+import static org.briarproject.android.blogs.BasePostFragment.POST_ID;
 import static org.briarproject.android.util.AndroidUtils.TEASER_LENGTH;
 import static org.briarproject.android.util.AndroidUtils.getSpanned;
 import static org.briarproject.android.util.AndroidUtils.getTeaser;

briar-android/src/org/briarproject/android/blogs/FeedController.java

@@ -1,8 +1,11 @@
 package org.briarproject.android.blogs;
 
+import android.support.annotation.UiThread;
+
 import org.briarproject.android.controller.handler.ResultExceptionHandler;
 import org.briarproject.api.blogs.Blog;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.NotNullByDefault;
 
 import java.util.Collection;
 
@@ -13,4 +16,12 @@ public interface FeedController extends BaseController {
 
 	void loadPersonalBlog(ResultExceptionHandler<Blog, DbException> handler);
 
+	void setFeedListener(FeedListener listener);
+
+	@NotNullByDefault
+	interface FeedListener extends BlogListener {
+
+		@UiThread
+		void onBlogAdded();
+	}
 }

briar-android/src/org/briarproject/android/blogs/FeedControllerImpl.java

@@ -11,6 +11,7 @@ import org.briarproject.api.db.NoSuchMessageException;
 import org.briarproject.api.event.BlogPostAddedEvent;
 import org.briarproject.api.event.Event;
 import org.briarproject.api.event.EventBus;
+import org.briarproject.api.event.GroupAddedEvent;
 import org.briarproject.api.event.GroupRemovedEvent;
 import org.briarproject.api.identity.Author;
 import org.briarproject.api.identity.IdentityManager;
@@ -33,6 +34,8 @@ class FeedControllerImpl extends BaseControllerImpl
 	private static final Logger LOG =
 			Logger.getLogger(FeedControllerImpl.class.getName());
 
+	private volatile FeedListener listener;
+
 	@Inject
 	FeedControllerImpl(@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager, EventBus eventBus,
@@ -45,6 +48,7 @@ class FeedControllerImpl extends BaseControllerImpl
 	@Override
 	public void onStart() {
 		super.onStart();
+		if (listener == null) throw new IllegalStateException();
 		notificationManager.blockAllBlogPostNotifications();
 		notificationManager.clearAllBlogPostNotifications();
 	}
@@ -55,12 +59,24 @@ class FeedControllerImpl extends BaseControllerImpl
 		notificationManager.unblockAllBlogPostNotifications();
 	}
 
+	@Override
+	public void setFeedListener(FeedListener listener) {
+		super.setBlogListener(listener);
+		this.listener = listener;
+	}
+
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof BlogPostAddedEvent) {
 			BlogPostAddedEvent b = (BlogPostAddedEvent) e;
 			LOG.info("Blog post added");
 			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");
+				onBlogAdded();
+			}
 		} else if (e instanceof GroupRemovedEvent) {
 			GroupRemovedEvent g = (GroupRemovedEvent) e;
 			if (g.getGroup().getClientId().equals(CLIENT_ID)) {
@@ -70,6 +86,15 @@ class FeedControllerImpl extends BaseControllerImpl
 		}
 	}
 
+	private void onBlogAdded() {
+		listener.runOnUiThreadUnlessDestroyed(new Runnable() {
+			@Override
+			public void run() {
+				listener.onBlogAdded();
+			}
+		});
+	}
+
 	@Override
 	public void loadBlogPosts(
 			final ResultExceptionHandler<Collection<BlogPostItem>, DbException> handler) {

briar-android/src/org/briarproject/android/blogs/FeedFragment.java

@@ -3,6 +3,7 @@ package org.briarproject.android.blogs;
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
 import android.support.design.widget.Snackbar;
 import android.support.v4.app.ActivityOptionsCompat;
 import android.support.v4.content.ContextCompat;
@@ -17,14 +18,16 @@ import android.view.ViewGroup;
 
 import org.briarproject.R;
 import org.briarproject.android.ActivityComponent;
-import org.briarproject.android.blogs.BaseController.OnBlogPostAddedListener;
 import org.briarproject.android.blogs.BlogPostAdapter.OnBlogPostClickListener;
+import org.briarproject.android.blogs.FeedController.FeedListener;
 import org.briarproject.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.android.fragment.BaseFragment;
 import org.briarproject.android.view.BriarRecyclerView;
 import org.briarproject.api.blogs.Blog;
 import org.briarproject.api.blogs.BlogPostHeader;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.api.nullsafety.ParametersNotNullByDefault;
 
 import java.util.Collection;
 import java.util.logging.Logger;
@@ -37,8 +40,11 @@ import static android.support.v4.app.ActivityOptionsCompat.makeCustomAnimation;
 import static org.briarproject.android.BriarActivity.GROUP_ID;
 import static org.briarproject.android.blogs.BlogActivity.REQUEST_WRITE_POST;
 
+@UiThread
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class FeedFragment extends BaseFragment implements
-		OnBlogPostClickListener, OnBlogPostAddedListener {
+		OnBlogPostClickListener, FeedListener {
 
 	public final static String TAG = FeedFragment.class.getName();
 	private static final Logger LOG = Logger.getLogger(TAG);
@@ -62,8 +68,9 @@ public class FeedFragment extends BaseFragment implements
 
 	@Nullable
 	@Override
-	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+	public View onCreateView(LayoutInflater inflater,
-			Bundle savedInstanceState) {
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
 
 		View v = inflater.inflate(R.layout.fragment_blog, container, false);
 
@@ -81,7 +88,7 @@ public class FeedFragment extends BaseFragment implements
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
-		feedController.setOnBlogPostAddedListener(this);
+		feedController.setFeedListener(this);
 	}
 
 	@Override
@@ -216,8 +223,8 @@ public class FeedFragment extends BaseFragment implements
 
 	@Override
 	public void onBlogPostClick(BlogPostItem post) {
-		FeedPostPagerFragment f = FeedPostPagerFragment
+		FeedPostFragment f =
-				.newInstance(post.getId());
+				FeedPostFragment.newInstance(post.getGroupId(), post.getId());
 		getActivity().getSupportFragmentManager().beginTransaction()
 				.replace(R.id.content_fragment, f, f.getUniqueTag())
 				.addToBackStack(f.getUniqueTag())
@@ -253,6 +260,11 @@ public class FeedFragment extends BaseFragment implements
 		s.show();
 	}
 
+	@Override
+	public void onBlogAdded() {
+		loadBlogPosts(false);
+	}
+
 	@Override
 	public void onBlogRemoved() {
 		loadBlogPosts(true);

briar-android/src/org/briarproject/android/blogs/FeedPostFragment.java

@@ -2,6 +2,7 @@ package org.briarproject.android.blogs;
 
 import android.os.Bundle;
 import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -9,17 +10,21 @@ import android.view.ViewGroup;
 import org.briarproject.android.ActivityComponent;
 import org.briarproject.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.MessageId;
 
 import javax.inject.Inject;
 
 import static org.briarproject.android.BriarActivity.GROUP_ID;
-import static org.briarproject.android.blogs.BasePostPagerFragment.POST_ID;
 
+@UiThread
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class FeedPostFragment extends BasePostFragment {
 
-	public final static String TAG = FeedPostFragment.class.getName();
+	private static final String TAG = FeedPostFragment.class.getName();
 
 	private MessageId postId;
 	private GroupId blogId;
@@ -40,8 +45,9 @@ public class FeedPostFragment extends BasePostFragment {
 
 	@Nullable
 	@Override
-	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+	public View onCreateView(LayoutInflater inflater,
-			Bundle savedInstanceState) {
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
 
 		Bundle args = getArguments();
 		byte[] b = args.getByteArray(GROUP_ID);
@@ -55,6 +61,11 @@ public class FeedPostFragment extends BasePostFragment {
 		return super.onCreateView(inflater, container, savedInstanceState);
 	}
 
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
@@ -70,16 +81,12 @@ public class FeedPostFragment extends BasePostFragment {
 					public void onResultUi(BlogPostItem post) {
 						onBlogPostLoaded(post);
 					}
+
 					@Override
 					public void onExceptionUi(DbException exception) {
-						onBlogPostLoadException(exception);
+						// TODO: Decide how to handle errors in the UI
 					}
 				});
 	}
 
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
 }

briar-android/src/org/briarproject/android/blogs/FeedPostPagerFragment.java

@@ -1,89 +0,0 @@
-package org.briarproject.android.blogs;
-
-import android.os.Bundle;
-
-import org.briarproject.android.ActivityComponent;
-import org.briarproject.android.controller.handler.UiResultExceptionHandler;
-import org.briarproject.api.blogs.BlogPostHeader;
-import org.briarproject.api.db.DbException;
-import org.briarproject.api.sync.MessageId;
-
-import java.util.Collection;
-
-import javax.inject.Inject;
-
-public class FeedPostPagerFragment extends BasePostPagerFragment {
-
-	public final static String TAG = FeedPostPagerFragment.class.getName();
-
-	@Inject
-	FeedController feedController;
-
-	static FeedPostPagerFragment newInstance(MessageId postId) {
-		FeedPostPagerFragment f = new FeedPostPagerFragment();
-
-		Bundle args = new Bundle();
-		args.putByteArray(POST_ID, postId.getBytes());
-		f.setArguments(args);
-
-		return f;
-	}
-
-	@Override
-	public void injectFragment(ActivityComponent component) {
-		component.inject(this);
-		feedController.setOnBlogPostAddedListener(this);
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		feedController.onStart();
-	}
-
-	@Override
-	public void onStop() {
-		super.onStop();
-		feedController.onStop();
-	}
-
-	@Override
-	void loadBlogPosts(final MessageId select) {
-		feedController.loadBlogPosts(
-				new UiResultExceptionHandler<Collection<BlogPostItem>, DbException>(
-						this) {
-					@Override
-					public void onResultUi(Collection<BlogPostItem> posts) {
-						onBlogPostsLoaded(select, posts);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						onBlogPostsLoadedException(exception);
-					}
-				});
-	}
-
-	@Override
-	void loadBlogPost(BlogPostHeader header) {
-		feedController.loadBlogPost(header,
-				new UiResultExceptionHandler<BlogPostItem, DbException>(
-						this) {
-					@Override
-					public void onResultUi(BlogPostItem post) {
-						addPost(post);
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						// TODO: Decide how to handle errors in the UI
-						finish();
-					}
-				});
-	}
-}

briar-android/src/org/briarproject/android/blogs/ReblogActivity.java

@@ -15,7 +15,7 @@ import org.briarproject.android.fragment.BaseFragment.BaseFragmentListener;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.MessageId;
 
-import static org.briarproject.android.blogs.BasePostPagerFragment.POST_ID;
+import static org.briarproject.android.blogs.BasePostFragment.POST_ID;
 
 public class ReblogActivity extends BriarActivity implements
 		BaseFragmentListener {

briar-android/src/org/briarproject/android/blogs/ReblogFragment.java

@@ -28,7 +28,7 @@ import static android.view.View.GONE;
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.android.BriarActivity.GROUP_ID;
-import static org.briarproject.android.blogs.BasePostPagerFragment.POST_ID;
+import static org.briarproject.android.blogs.BasePostFragment.POST_ID;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault