Allow DbViewModel work on things other than lists.

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

@@ -53,13 +53,9 @@ abstract class BaseViewModel extends DbViewModel implements EventListener {
 	protected final AndroidNotificationManager notificationManager;
 	protected final BlogManager blogManager;
 
-	protected final MutableLiveData<LiveResult<List<BlogPostItem>>> blogPosts =
+	protected final MutableLiveData<LiveResult<ListUpdate>> blogPosts =
 			new MutableLiveData<>();
 
-	// UI thread
-	@Nullable
-	private Boolean postAddedWasLocal = null;
-
 	BaseViewModel(Application application,
 			@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager,
@@ -147,11 +143,10 @@ abstract class BaseViewModel extends DbViewModel implements EventListener {
 
 	@UiThread
 	private void onBlogPostItemAdded(BlogPostItem item, boolean local) {
-		List<BlogPostItem> items = addListItem(blogPosts, item);
+		List<BlogPostItem> items = addListItem(getBlogPostItems(), item);
 		if (items != null) {
 			Collections.sort(items);
-			postAddedWasLocal = local;
-			blogPosts.setValue(new LiveResult<>(items));
+			blogPosts.setValue(new LiveResult<>(new ListUpdate(local, items)));
 		}
 	}
 
@@ -168,17 +163,37 @@ abstract class BaseViewModel extends DbViewModel implements EventListener {
 		});
 	}
 
-	LiveData<LiveResult<List<BlogPostItem>>> getBlogPosts() {
+	LiveData<LiveResult<ListUpdate>> getBlogPosts() {
 		return blogPosts;
 	}
 
 	@UiThread
-	@Nullable
-	Boolean getPostAddedWasLocalAndReset() {
-		if (postAddedWasLocal == null) return null;
-		boolean wasLocal = postAddedWasLocal;
-		postAddedWasLocal = null;
-		return wasLocal;
+	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/BlogFragment.java

@@ -15,6 +15,7 @@ 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.blog.BaseViewModel.ListUpdate;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.sharing.BlogSharingStatusActivity;
 import org.briarproject.briar.android.sharing.ShareBlogActivity;
@@ -22,8 +23,6 @@ import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.widget.LinkDialogFragment;
 
-import java.util.List;
-
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
@@ -174,9 +173,9 @@ public class BlogFragment extends BaseFragment
 		return TAG;
 	}
 
-	private void onBlogPostsLoaded(List<BlogPostItem> items) {
-		adapter.submitList(items, () -> {
-			Boolean wasLocal = viewModel.getPostAddedWasLocalAndReset();
+	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,

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

@@ -145,7 +145,8 @@ class BlogViewModel extends BaseViewModel {
 	}
 
 	private void loadBlogPosts(GroupId groupId) {
-		loadList(txn -> loadBlogPosts(txn, groupId), blogPosts::setValue);
+		loadList(txn -> new ListUpdate(null, loadBlogPosts(txn, groupId)),
+				blogPosts::setValue);
 	}
 
 	private void loadSharingContacts(GroupId groupId) {

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

@@ -13,14 +13,13 @@ 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.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 java.util.List;
-
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
@@ -101,10 +100,9 @@ public class FeedFragment extends BaseFragment
 		list.stopPeriodicUpdate();
 	}
 
-	private void onBlogPostsLoaded(List<BlogPostItem> items) {
-		if (items.isEmpty()) list.showData();
-		else adapter.submitList(items, () -> {
-			Boolean wasLocal = viewModel.getPostAddedWasLocalAndReset();
+	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) {

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

@@ -13,7 +13,6 @@ 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.GroupAddedEvent;
 import org.briarproject.bramble.api.sync.event.GroupRemovedEvent;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.briar.android.viewmodel.LiveResult;
@@ -34,10 +33,8 @@ 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.api.blog.BlogManager.CLIENT_ID;
 
@@ -70,15 +67,8 @@ class FeedViewModel extends BaseViewModel {
 			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");
-				// TODO how can this even happen?
-				//  added RSS feeds should trigger BlogPostAddedEvent, no?
-				onBlogAdded(g.getGroup().getId());
-			}
-		} else if (e instanceof GroupRemovedEvent) {
+		}
+		if (e instanceof GroupRemovedEvent) {
 			GroupRemovedEvent g = (GroupRemovedEvent) e;
 			if (g.getGroup().getClientId().equals(CLIENT_ID)) {
 				LOG.info("Blog removed");
@@ -119,7 +109,7 @@ class FeedViewModel extends BaseViewModel {
 	}
 
 	@DatabaseExecutor
-	private List<BlogPostItem> loadAllBlogPosts(Transaction txn)
+	private ListUpdate loadAllBlogPosts(Transaction txn)
 			throws DbException {
 		long start = now();
 		List<BlogPostItem> posts = new ArrayList<>();
@@ -128,29 +118,17 @@ class FeedViewModel extends BaseViewModel {
 		}
 		Collections.sort(posts);
 		logDuration(LOG, "Loading all posts", start);
-		return posts;
-	}
-
-	private void onBlogAdded(GroupId g) {
-		runOnDbThread(true, txn -> {
-			List<BlogPostItem> posts = loadBlogPosts(txn, g);
-			txn.attach(() -> onBlogPostItemsAdded(posts));
-		}, e -> logException(LOG, WARNING, e));
+		return new ListUpdate(null, posts);
 	}
 
 	@UiThread
-	private void onBlogPostItemsAdded(List<BlogPostItem> posts) {
-		List<BlogPostItem> items = addListItems(blogPosts, posts);
+	private void onBlogRemoved(GroupId g) {
+		List<BlogPostItem> items = removeListItems(getBlogPostItems(),
+				item -> item.getGroupId().equals(g)
+		);
 		if (items != null) {
-			Collections.sort(items);
-			blogPosts.setValue(new LiveResult<>(items));
+			blogPosts.setValue(new LiveResult<>(new ListUpdate(null, items)));
 		}
 	}
 
-	private void onBlogRemoved(GroupId g) {
-		removeAndUpdateListItems(blogPosts, item ->
-				item.getGroupId().equals(g)
-		);
-	}
-
 }

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/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;

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;

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

@@ -120,9 +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 {
@@ -149,63 +151,46 @@ public abstract class DbViewModel extends AndroidViewModel {
 	}
 
 	/**
-	 * Creates a copy of the list available in the given LiveData
-	 * and adds the given item to the copy.
+	 * 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 added or null when
-	 * <ul>
-	 * <li> LiveData does not have a value
-	 * <li> LiveResult in the LiveData has an error
-	 * </ul>
+	 * @return an updated copy of the list, or null if the list is null
 	 */
 	@Nullable
-	protected <T> List<T> addListItem(LiveData<LiveResult<List<T>>> liveData,
-			T item) {
-		List<T> items = getListCopy(liveData);
-		if (items == null) return null;
-		items.add(item);
-		return items;
+	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;
 	}
 
 	/**
-	 * Creates a copy of the list available in the given LiveData
-	 * and adds the given items to the copy.
+	 * Creates a copy of the given list and adds the given items to the copy.
 	 *
-	 * @return a copy of the list in the LiveData with items added or null when
-	 * <ul>
-	 * <li> LiveData does not have a value
-	 * <li> LiveResult in the LiveData has an error
-	 * </ul>
+	 * @return an updated copy of the list, or null if the list is null
 	 */
 	@Nullable
-	protected <T> List<T> addListItems(LiveData<LiveResult<List<T>>> liveData,
+	protected <T> List<T> addListItems(@Nullable List<T> list,
 			Collection<T> items) {
-		List<T> copiedItems = getListCopy(liveData);
-		if (copiedItems == null) return null;
-		copiedItems.addAll(items);
-		return copiedItems;
+		if (list == null) return null;
+		List<T> copy = new ArrayList<>(list);
+		copy.addAll(items);
+		return copy;
 	}
 
 	/**
-	 * 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, replacing items where the given test
+	 * function returns true.
 	 *
-	 * @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 either the list is null
+	 * or the test function returns false for all items
 	 */
 	@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> 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 = items.listIterator();
+		ListIterator<T> iterator = copy.listIterator();
 		boolean changed = false;
 		while (iterator.hasNext()) {
 			T item = iterator.next();
@@ -214,28 +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();
@@ -244,7 +224,7 @@ public abstract class DbViewModel extends AndroidViewModel {
 				iterator.remove();
 			}
 		}
-		return changed ? items : null;
+		return changed ? copy : null;
 	}
 
 	/**
@@ -255,29 +235,26 @@ public abstract class DbViewModel extends AndroidViewModel {
 	 * <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
+	 * <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> list = removeListItems(liveData, test);
-		if (list != null) liveData.setValue(new LiveResult<>(list));
+		List<T> copy = removeListItems(getList(liveData), test);
+		if (copy != null) liveData.setValue(new LiveResult<>(copy));
 	}
 
 	/**
-	 * 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.
+	 * 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();
 	}
 
 	/**