Submit thread list items to ListAdapter

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

@@ -19,7 +19,6 @@ import org.briarproject.briar.android.threaded.ThreadItemAdapter;
 import org.briarproject.briar.android.threaded.ThreadListActivity;
 import org.briarproject.briar.android.threaded.ThreadListController;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
-import org.briarproject.briar.api.forum.Forum;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
@@ -37,7 +36,7 @@ import static org.briarproject.briar.api.forum.ForumConstants.MAX_FORUM_POST_TEX
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class ForumActivity extends
-		ThreadListActivity<Forum, ForumPostItem, ThreadItemAdapter<ForumPostItem>>
+		ThreadListActivity<ForumPostItem, ThreadItemAdapter<ForumPostItem>>
 		implements ForumListener {
 
 	@Inject
@@ -55,12 +54,12 @@ public class ForumActivity extends
 	}
 
 	@Override
-	protected ThreadListController<Forum, ForumPostItem> getController() {
+	protected ThreadListController<ForumPostItem> getController() {
 		return forumController;
 	}
 
 	@Override
-	protected ThreadListViewModel<Forum, ForumPostItem> getViewModel() {
+	protected ThreadListViewModel<ForumPostItem> getViewModel() {
 		return viewModel;
 	}
 

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

@@ -3,12 +3,11 @@ package org.briarproject.briar.android.forum;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.threaded.ThreadListController;
-import org.briarproject.briar.api.forum.Forum;
 
 import androidx.annotation.UiThread;
 
 @NotNullByDefault
-interface ForumController extends ThreadListController<Forum, ForumPostItem> {
+interface ForumController extends ThreadListController<ForumPostItem> {
 
 	interface ForumListener extends ThreadListListener<ForumPostItem> {
 		@UiThread

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

@@ -19,7 +19,6 @@ import org.briarproject.briar.android.threaded.ThreadListControllerImpl;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.MessageTracker.GroupCount;
-import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumInvitationResponse;
 import org.briarproject.briar.api.forum.ForumManager;
 import org.briarproject.briar.api.forum.ForumPost;
@@ -43,7 +42,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 class ForumControllerImpl extends
-		ThreadListControllerImpl<Forum, ForumPostItem, ForumPostHeader, ForumPost, ForumListener>
+		ThreadListControllerImpl<ForumPostItem, ForumPostHeader, ForumPost, ForumListener>
 		implements ForumController {
 
 	private static final Logger LOG =
@@ -98,16 +97,6 @@ class ForumControllerImpl extends
 		}
 	}
 
-	@Override
-	protected Collection<ForumPostHeader> loadHeaders() throws DbException {
-		return forumManager.getPostHeaders(getGroupId());
-	}
-
-	@Override
-	protected String loadMessageText(ForumPostHeader h) throws DbException {
-		return forumManager.getPostText(h.getId());
-	}
-
 	@Override
 	protected void markRead(MessageId id) throws DbException {
 		forumManager.setReadFlag(getGroupId(), id, true);

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

@@ -6,6 +6,7 @@ import android.widget.Toast;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 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;
@@ -18,10 +19,15 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
+import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.client.PostHeader;
 import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumManager;
+import org.briarproject.briar.api.forum.ForumPostHeader;
 import org.briarproject.briar.api.forum.ForumSharingManager;
+import org.briarproject.briar.client.MessageTreeImpl;
 
+import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -33,11 +39,13 @@ import androidx.lifecycle.MutableLiveData;
 import static android.widget.Toast.LENGTH_SHORT;
 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 ForumViewModel extends ThreadListViewModel<Forum, ForumPostItem> {
+class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 
 	private static final Logger LOG = getLogger(ForumViewModel.class.getName());
 
@@ -54,12 +62,13 @@ class ForumViewModel extends ThreadListViewModel<Forum, ForumPostItem> {
 			AndroidNotificationManager notificationManager,
 			@CryptoExecutor Executor cryptoExecutor,
 			Clock clock,
+			MessageTracker messageTracker,
 			EventBus eventBus,
 			ForumManager forumManager,
 			ForumSharingManager forumSharingManager) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
 				identityManager, notificationManager, cryptoExecutor, clock,
-				eventBus);
+				messageTracker, eventBus);
 		this.forumManager = forumManager;
 		this.forumSharingManager = forumSharingManager;
 	}
@@ -82,6 +91,29 @@ class ForumViewModel extends ThreadListViewModel<Forum, ForumPostItem> {
 		return forum;
 	}
 
+	@Override
+	public void loadItems() {
+		loadList(txn -> {
+			long start = now();
+			List<ForumPostHeader> headers =
+					forumManager.getPostHeaders(txn, groupId);
+			logDuration(LOG, "Loading headers", start);
+			List<ForumPostItem> items =
+					buildItems(txn, headers, this::buildItem);
+			return new MessageTreeImpl<>(items).depthFirstOrder();
+		}, this::setItems);
+	}
+
+	private ForumPostItem buildItem(ForumPostHeader header, String text) {
+		return new ForumPostItem(header, text);
+	}
+
+	@Override
+	protected String loadMessageText(Transaction txn, PostHeader header)
+			throws DbException {
+		return forumManager.getPostText(txn, header.getId());
+	}
+
 	void deleteForum() {
 		runOnDbThread(() -> {
 			try {

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupActivity.java

@@ -21,7 +21,6 @@ import org.briarproject.briar.android.privategroup.reveal.RevealContactsActivity
 import org.briarproject.briar.android.threaded.ThreadListActivity;
 import org.briarproject.briar.android.threaded.ThreadListController;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
-import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.Visibility;
 
 import javax.annotation.Nullable;
@@ -41,7 +40,7 @@ import static org.briarproject.briar.api.privategroup.PrivateGroupConstants.MAX_
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class GroupActivity extends
-		ThreadListActivity<PrivateGroup, GroupMessageItem, GroupMessageAdapter>
+		ThreadListActivity<GroupMessageItem, GroupMessageAdapter>
 		implements GroupListener {
 
 	@Inject
@@ -65,12 +64,12 @@ public class GroupActivity extends
 	}
 
 	@Override
-	protected ThreadListController<PrivateGroup, GroupMessageItem> getController() {
+	protected ThreadListController<GroupMessageItem> getController() {
 		return controller;
 	}
 
 	@Override
-	protected ThreadListViewModel<PrivateGroup, GroupMessageItem> getViewModel() {
+	protected ThreadListViewModel<GroupMessageItem> getViewModel() {
 		return viewModel;
 	}
 
@@ -103,22 +102,11 @@ public class GroupActivity extends
 		}
 
 		setGroupEnabled(false);
-	}
-
-	@Override
-	protected GroupMessageAdapter createAdapter(
-			LinearLayoutManager layoutManager) {
-		return new GroupMessageAdapter(this, layoutManager);
-	}
-
-	@Override
-	protected void loadItems() {
 		controller.isDissolved(
 				new UiResultExceptionHandler<Boolean, DbException>(this) {
 					@Override
 					public void onResultUi(Boolean isDissolved) {
 						setGroupEnabled(!isDissolved);
-						GroupActivity.super.loadItems();
 					}
 
 					@Override
@@ -128,6 +116,12 @@ public class GroupActivity extends
 				});
 	}
 
+	@Override
+	protected GroupMessageAdapter createAdapter(
+			LinearLayoutManager layoutManager) {
+		return new GroupMessageAdapter(this, layoutManager);
+	}
+
 	@Override
 	public boolean onCreateOptionsMenu(Menu menu) {
 		// Inflate the menu items for use in the action bar

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupController.java

@@ -5,13 +5,12 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
 import org.briarproject.briar.android.threaded.ThreadListController;
-import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.Visibility;
 
 import androidx.annotation.UiThread;
 
 public interface GroupController
-		extends ThreadListController<PrivateGroup, GroupMessageItem> {
+		extends ThreadListController<GroupMessageItem> {
 
 	void isDissolved(
 			ResultExceptionHandler<Boolean, DbException> handler);

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupControllerImpl.java

@@ -24,7 +24,6 @@ import org.briarproject.briar.api.privategroup.GroupMessage;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.GroupMessageHeader;
 import org.briarproject.briar.api.privategroup.JoinMessageHeader;
-import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
 import org.briarproject.briar.api.privategroup.event.ContactRelationshipRevealedEvent;
 import org.briarproject.briar.api.privategroup.event.GroupDissolvedEvent;
@@ -47,7 +46,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 class GroupControllerImpl extends
-		ThreadListControllerImpl<PrivateGroup, GroupMessageItem, GroupMessageHeader, GroupMessage, GroupListener>
+		ThreadListControllerImpl<GroupMessageItem, GroupMessageHeader, GroupMessage, GroupListener>
 		implements GroupController {
 
 	private static final Logger LOG =
@@ -108,21 +107,6 @@ class GroupControllerImpl extends
 		}
 	}
 
-	@Override
-	protected Collection<GroupMessageHeader> loadHeaders() throws DbException {
-		return privateGroupManager.getHeaders(getGroupId());
-	}
-
-	@Override
-	protected String loadMessageText(GroupMessageHeader header)
-			throws DbException {
-		if (header instanceof JoinMessageHeader) {
-			// will be looked up later
-			return "";
-		}
-		return privateGroupManager.getMessageText(header.getId());
-	}
-
 	@Override
 	protected void markRead(MessageId id) throws DbException {
 		privateGroupManager.setReadFlag(getGroupId(), id, true);

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupMessageAdapter.java

@@ -32,7 +32,7 @@ class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
 	@LayoutRes
 	@Override
 	public int getItemViewType(int position) {
-		GroupMessageItem item = items.get(position);
+		GroupMessageItem item = getItem(position);
 		return item.getLayout();
 	}
 
@@ -55,7 +55,7 @@ class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
 	void updateVisibility(AuthorId memberId, Visibility v) {
 		int position = findItemPosition(memberId);
 		if (position != NO_POSITION) {
-			GroupMessageItem item = items.get(position);
+			GroupMessageItem item = getItem(position);
 			if (item instanceof JoinMessageItem) {
 				((JoinMessageItem) item).setVisibility(v);
 				notifyItemChanged(findItemPosition(item), item);
@@ -63,14 +63,22 @@ class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
 		}
 	}
 
+	@Deprecated
 	private int findItemPosition(AuthorId a) {
-		int count = items.size();
+		for (int i = 0; i < getItemCount(); i++) {
-		for (int i = 0; i < count; i++) {
+			GroupMessageItem item = getItem(i);
-			GroupMessageItem item = items.get(i);
 			if (item.getAuthor().getId().equals(a))
 				return i;
 		}
 		return NO_POSITION; // Not found
 	}
 
+	@Deprecated
+	private int findItemPosition(GroupMessageItem itemToFind) {
+		for (int i = 0; i < getItemCount(); i++) {
+			if (getItem(i).equals(itemToFind)) return i;
+		}
+		return NO_POSITION; // Not found
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupViewModel.java

@@ -5,6 +5,7 @@ import android.app.Application;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 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;
@@ -18,10 +19,16 @@ import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
+import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.client.PostHeader;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
+import org.briarproject.briar.api.privategroup.GroupMessageHeader;
+import org.briarproject.briar.api.privategroup.JoinMessageHeader;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
+import org.briarproject.briar.client.MessageTreeImpl;
 
+import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -32,20 +39,22 @@ 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 GroupViewModel
+class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
-		extends ThreadListViewModel<PrivateGroup, GroupMessageItem> {
 
 	private static final Logger LOG = getLogger(GroupViewModel.class.getName());
 
 	private final PrivateGroupManager privateGroupManager;
 	private final GroupMessageFactory groupMessageFactory;
 
-	MutableLiveData<PrivateGroup> privateGroup = new MutableLiveData<>();
+	private final MutableLiveData<PrivateGroup> privateGroup =
-	MutableLiveData<Boolean> isCreator = new MutableLiveData<>();
+			new MutableLiveData<>();
+	private final MutableLiveData<Boolean> isCreator = new MutableLiveData<>();
 
 	@Inject
 	GroupViewModel(Application application,
@@ -58,11 +67,12 @@ class GroupViewModel
 			AndroidNotificationManager notificationManager,
 			@CryptoExecutor Executor cryptoExecutor,
 			Clock clock,
+			MessageTracker messageTracker,
 			PrivateGroupManager privateGroupManager,
 			GroupMessageFactory groupMessageFactory) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
 				identityManager, notificationManager, cryptoExecutor, clock,
-				eventBus);
+				messageTracker, eventBus);
 		this.privateGroupManager = privateGroupManager;
 		this.groupMessageFactory = groupMessageFactory;
 	}
@@ -91,6 +101,37 @@ class GroupViewModel
 		});
 	}
 
+	@Override
+	public void loadItems() {
+		loadList(txn -> {
+			// TODO first check if group is dissolved
+			long start = now();
+			List<GroupMessageHeader> headers =
+					privateGroupManager.getHeaders(txn, groupId);
+			logDuration(LOG, "Loading headers", start);
+			List<GroupMessageItem> items =
+					buildItems(txn, headers, this::buildItem);
+			return new MessageTreeImpl<>(items).depthFirstOrder();
+		}, this::setItems);
+	}
+
+	private GroupMessageItem buildItem(GroupMessageHeader header, String text) {
+		if (header instanceof JoinMessageHeader) {
+			return new JoinMessageItem((JoinMessageHeader) header, text);
+		}
+		return new GroupMessageItem(header, text);
+	}
+
+	@Override
+	protected String loadMessageText(
+			Transaction txn, PostHeader header) throws DbException {
+		if (header instanceof JoinMessageHeader) {
+			// will be looked up later
+			return "";
+		}
+		return privateGroupManager.getMessageText(txn, header.getId());
+	}
+
 	void deletePrivateGroup() {
 		runOnDbThread(() -> {
 			try {

briar-android/src/main/java/org/briarproject/briar/android/threaded/NestedTreeList.java

@@ -1,54 +0,0 @@
-package org.briarproject.briar.android.threaded;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.api.client.MessageTree;
-import org.briarproject.briar.api.client.MessageTree.MessageNode;
-import org.briarproject.briar.client.MessageTreeImpl;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Iterator;
-import java.util.List;
-
-import androidx.annotation.UiThread;
-
-@UiThread
-@NotNullByDefault
-public class NestedTreeList<T extends MessageNode> implements Iterable<T> {
-
-	private final MessageTree<T> tree = new MessageTreeImpl<>();
-	private List<T> depthFirstCollection = new ArrayList<>();
-
-	public void addAll(Collection<T> collection) {
-		tree.add(collection);
-		depthFirstCollection = new ArrayList<>(tree.depthFirstOrder());
-	}
-
-	public void add(T elem) {
-		tree.add(elem);
-		depthFirstCollection = new ArrayList<>(tree.depthFirstOrder());
-	}
-
-	public void clear() {
-		tree.clear();
-		depthFirstCollection.clear();
-	}
-
-	public T get(int index) {
-		return depthFirstCollection.get(index);
-	}
-
-	public int size() {
-		return depthFirstCollection.size();
-	}
-
-	public boolean contains(MessageId m) {
-		return tree.contains(m);
-	}
-
-	@Override
-	public Iterator<T> iterator() {
-		return depthFirstCollection.iterator();
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadItem.java

@@ -99,4 +99,14 @@ public abstract class ThreadItem implements MessageNode {
 		return highlighted;
 	}
 
+	@Override
+	public int hashCode() {
+		return messageId.hashCode();
+	}
+
+	@Override
+	public boolean equals(@Nullable Object o) {
+		return o instanceof ThreadItem &&
+				messageId.equals(((ThreadItem) o).messageId);
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadItemAdapter.java

@@ -4,37 +4,48 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
+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.util.ItemReturningAdapter;
-import org.briarproject.briar.android.util.VersionedAdapter;
-
-import java.util.Collection;
 
 import javax.annotation.Nullable;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
+import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.LinearLayoutManager;
-import androidx.recyclerview.widget.RecyclerView;
+import androidx.recyclerview.widget.ListAdapter;
 
 import static androidx.recyclerview.widget.RecyclerView.NO_POSITION;
 
 @UiThread
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class ThreadItemAdapter<I extends ThreadItem>
-		extends RecyclerView.Adapter<BaseThreadItemViewHolder<I>>
+		extends ListAdapter<I, BaseThreadItemViewHolder<I>>
-		implements VersionedAdapter, ItemReturningAdapter<I> {
+		implements ItemReturningAdapter<I> {
 
 	static final int UNDEFINED = -1;
 
-	protected final NestedTreeList<I> items = new NestedTreeList<>();
 	private final ThreadItemListener<I> listener;
 	private final LinearLayoutManager layoutManager;
 
-	private volatile int revision = 0;
-
 	public ThreadItemAdapter(ThreadItemListener<I> listener,
 			LinearLayoutManager layoutManager) {
+		super(new DiffUtil.ItemCallback<I>() {
+			@Override
+			public boolean areItemsTheSame(I a, I b) {
+				return a.equals(b);
+			}
+
+			@Override
+			public boolean areContentsTheSame(I a, I b) {
+				return a.isHighlighted() == b.isHighlighted() &&
+						a.isRead() && b.isRead();
+			}
+		});
 		this.listener = listener;
 		this.layoutManager = layoutManager;
 	}
@@ -51,28 +62,14 @@ public class ThreadItemAdapter<I extends ThreadItem>
 	@Override
 	public void onBindViewHolder(@NonNull BaseThreadItemViewHolder<I> ui,
 			int position) {
-		I item = items.get(position);
+		I item = getItem(position);
 		ui.bind(item, listener);
 	}
 
-	@Override
-	public int getItemCount() {
-		return items.size();
-	}
-
-	@Override
-	public int getRevision() {
-		return revision;
-	}
-
-	@Override
-	public void incrementRevision() {
-		revision++;
-	}
-
 	void setItemWithIdVisible(MessageId messageId) {
 		int pos = 0;
-		for (I item : items) {
+		for (int i = 0; i < getItemCount(); i++) {
+			I item = getItem(i);
 			if (item.getId().equals(messageId)) {
 				layoutManager.scrollToPosition(pos);
 				break;
@@ -81,46 +78,16 @@ public class ThreadItemAdapter<I extends ThreadItem>
 		}
 	}
 
-	public void setItems(Collection<I> items) {
-		this.items.clear();
-		this.items.addAll(items);
-		notifyDataSetChanged();
-	}
-
-	public void add(I item) {
-		items.add(item);
-		notifyItemInserted(findItemPosition(item));
-	}
-
-	@Nullable
-	public I getItemAt(int position) {
-		if (position == NO_POSITION || position >= items.size()) {
-			return null;
-		}
-		return items.get(position);
-	}
-
-	protected int findItemPosition(@Nullable I item) {
-		for (int i = 0; i < items.size(); i++) {
-			if (items.get(i).equals(item)) return i;
-		}
-		return NO_POSITION; // Not found
-	}
-
-	boolean contains(MessageId m) {
-		return items.contains(m);
-	}
-
 	/**
 	 * Highlights the item with the given {@link MessageId}
 	 * and disables the highlight for a previously highlighted item, if any.
-	 *
+	 * <p>
 	 * Only one item can be highlighted at a time.
 	 */
 	void setHighlightedItem(@Nullable MessageId id) {
-		for (int i = 0; i < items.size(); i++) {
+		for (int i = 0; i < getItemCount(); i++) {
-			I item = items.get(i);
+			I item = getItem(i);
-			if (id != null && item.getId().equals(id)) {
+			if (item.getId().equals(id)) {
 				item.setHighlighted(true);
 				notifyItemChanged(i, item);
 			} else if (item.isHighlighted()) {
@@ -132,8 +99,9 @@ public class ThreadItemAdapter<I extends ThreadItem>
 
 	@Nullable
 	I getHighlightedItem() {
-		for (I i : items) {
+		for (int i = 0; i < getItemCount(); i++) {
-			if (i.isHighlighted()) return i;
+			I item = getItem(i);
+			if (item.isHighlighted()) return item;
 		}
 		return null;
 	}
@@ -144,8 +112,8 @@ public class ThreadItemAdapter<I extends ThreadItem>
 	int getVisibleUnreadPosBottom() {
 		int positionBottom = layoutManager.findLastVisibleItemPosition();
 		if (positionBottom == NO_POSITION) return NO_POSITION;
-		for (int i = positionBottom + 1; i < items.size(); i++) {
+		for (int i = positionBottom + 1; i < getItemCount(); i++) {
-			if (!items.get(i).isRead()) return i;
+			if (!getItem(i).isRead()) return i;
 		}
 		return NO_POSITION;
 	}
@@ -156,8 +124,8 @@ public class ThreadItemAdapter<I extends ThreadItem>
 	int getVisibleUnreadPosTop() {
 		int positionTop = layoutManager.findFirstVisibleItemPosition();
 		int position = NO_POSITION;
-		for (int i = 0; i < items.size(); i++) {
+		for (int i = 0; i < getItemCount(); i++) {
-			if (i < positionTop && !items.get(i).isRead()) {
+			if (i < positionTop && !getItem(i).isRead()) {
 				position = i;
 			} else if (i >= positionTop) {
 				return position;
@@ -166,6 +134,11 @@ public class ThreadItemAdapter<I extends ThreadItem>
 		return NO_POSITION;
 	}
 
+	@Override
+	public I getItemAt(int position) {
+		return getItem(position);
+	}
+
 	public interface ThreadItemListener<I> {
 		void onReplyClick(I item);
 	}

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListActivity.java

@@ -28,7 +28,6 @@ import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.android.view.UnreadMessageButton;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
-import org.briarproject.briar.api.client.NamedGroup;
 
 import java.util.Collection;
 import java.util.List;
@@ -48,7 +47,7 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadItem, A extends ThreadItemAdapter<I>>
+public abstract class ThreadListActivity<I extends ThreadItem, A extends ThreadItemAdapter<I>>
 		extends BriarActivity
 		implements ThreadListListener<I>, SendListener, SharingListener,
 		ThreadItemListener<I>, ThreadListDataSource {
@@ -59,6 +58,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 			getLogger(ThreadListActivity.class.getName());
 
 	protected A adapter;
+
 	private ThreadScrollListener<I> scrollListener;
 	protected BriarRecyclerView list;
 	private LinearLayoutManager layoutManager;
@@ -70,9 +70,9 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	@Nullable
 	private MessageId replyId;
 
-	protected abstract ThreadListController<G, I> getController();
+	protected abstract ThreadListController<I> getController();
 
-	protected abstract ThreadListViewModel<G, I> getViewModel();
+	protected abstract ThreadListViewModel<I> getViewModel();
 
 	@Inject
 	protected SharingController sharingController;
@@ -127,6 +127,11 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 			if (replyIdBytes != null) replyId = new MessageId(replyIdBytes);
 		}
 
+		getViewModel().getItems().observe(this, result -> result
+				.onError(this::handleException)
+				.onSuccess(this::displayItems)
+		);
+
 		sharingController.setSharingListener(this);
 		loadSharingContacts();
 	}
@@ -145,44 +150,22 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 
 	protected abstract A createAdapter(LinearLayoutManager layoutManager);
 
-	protected void loadItems() {
+	protected void displayItems(List<I> items) {
-		int revision = adapter.getRevision();
+		if (items.isEmpty()) {
-		getController().loadItems(
+			list.showData();
-				new UiResultExceptionHandler<ThreadItemList<I>, DbException>(
-						this) {
-					@Override
-					public void onResultUi(ThreadItemList<I> items) {
-						if (revision == adapter.getRevision()) {
-							adapter.incrementRevision();
-							if (items.isEmpty()) {
-								list.showData();
-							} else {
-								displayItems(items);
-								updateTextInput();
-							}
-						} else {
-							LOG.info("Concurrent update, reloading");
-							loadItems();
-						}
-					}
-
-					@Override
-					public void onExceptionUi(DbException exception) {
-						handleException(exception);
-					}
-				});
-	}
-
-	private void displayItems(ThreadItemList<I> items) {
-		adapter.setItems(items);
-		MessageId messageId = items.getFirstVisibleItemId();
-		if (messageId != null)
-			adapter.setItemWithIdVisible(messageId);
-		list.showData();
-		if (layoutManagerState == null) {
-			list.scrollToPosition(0);  // Scroll to the top
 		} else {
-			layoutManager.onRestoreInstanceState(layoutManagerState);
+			adapter.submitList(items);
+			// TODO get this ID from elsewhere
+			MessageId messageId = null; // items.getFirstVisibleItemId();
+			if (messageId != null)
+				adapter.setItemWithIdVisible(messageId);
+			list.showData();
+			if (layoutManagerState == null) {
+				list.scrollToPosition(0);  // Scroll to the top
+			} else {
+				layoutManager.onRestoreInstanceState(layoutManagerState);
+			}
+			updateTextInput();
 		}
 	}
 
@@ -209,7 +192,6 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	public void onStart() {
 		super.onStart();
 		sharingController.onStart();
-		loadItems();
 		list.startPeriodicUpdate();
 	}
 
@@ -296,7 +278,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	}
 
 	private void scrollToItemAtTop(I item) {
-		int position = adapter.findItemPosition(item);
+		int position = NO_POSITION;// adapter.findItemPosition(item);
 		if (position != NO_POSITION) {
 			layoutManager
 					.scrollToPositionWithOffset(position, 0);
@@ -357,15 +339,14 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	}
 
 	private void addItem(I item, boolean isLocal) {
-		adapter.incrementRevision();
 		MessageId parent = item.getParentId();
-		if (parent != null && !adapter.contains(parent)) {
+		if (parent != null) {
 			// We've incremented the adapter's revision, so the item will be
 			// loaded when its parent has been loaded
 			LOG.info("Ignoring item with missing parent");
 			return;
 		}
-		adapter.add(item);
+		// TODO submit new list
 
 		if (isLocal) {
 			scrollToItemAtTop(item);

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListController.java

@@ -7,7 +7,6 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.controller.ActivityLifecycleController;
 import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
-import org.briarproject.briar.api.client.NamedGroup;
 
 import java.util.Collection;
 
@@ -16,7 +15,7 @@ import javax.annotation.Nullable;
 import androidx.annotation.UiThread;
 
 @NotNullByDefault
-public interface ThreadListController<G extends NamedGroup, I extends ThreadItem>
+public interface ThreadListController<I extends ThreadItem>
 		extends ActivityLifecycleController {
 
 	void setGroupId(GroupId groupId);
@@ -24,9 +23,6 @@ public interface ThreadListController<G extends NamedGroup, I extends ThreadItem
 	void loadSharingContacts(
 			ResultExceptionHandler<Collection<ContactId>, DbException> handler);
 
-	void loadItems(
-			ResultExceptionHandler<ThreadItemList<I>, DbException> handler);
-
 	void markItemRead(I item);
 
 	void markItemsRead(Collection<I> items);
@@ -48,7 +44,8 @@ public interface ThreadListController<G extends NamedGroup, I extends ThreadItem
 
 	interface ThreadListDataSource {
 
-		@UiThread @Nullable
+		@UiThread
+		@Nullable
 		MessageId getFirstVisibleMessageId();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListControllerImpl.java

@@ -21,7 +21,6 @@ import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
 import org.briarproject.briar.android.threaded.ThreadListController.ThreadListListener;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.client.MessageTracker;
-import org.briarproject.briar.api.client.NamedGroup;
 import org.briarproject.briar.api.client.PostHeader;
 import org.briarproject.briar.api.client.ThreadedMessage;
 
@@ -34,7 +33,6 @@ import java.util.logging.Logger;
 
 import androidx.annotation.CallSuper;
 
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -42,9 +40,9 @@ import static org.briarproject.bramble.util.LogUtils.now;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends ThreadItem, H extends PostHeader, M extends ThreadedMessage, L extends ThreadListListener<I>>
+public abstract class ThreadListControllerImpl<I extends ThreadItem, H extends PostHeader, M extends ThreadedMessage, L extends ThreadListListener<I>>
 		extends DbControllerImpl
-		implements ThreadListController<G, I>, EventListener {
+		implements ThreadListController<I>, EventListener {
 
 	private static final Logger LOG =
 			Logger.getLogger(ThreadListControllerImpl.class.getName());
@@ -129,42 +127,6 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 		}
 	}
 
-	@Override
-	public void loadItems(
-			ResultExceptionHandler<ThreadItemList<I>, DbException> handler) {
-		checkGroupId();
-		runOnDbThread(() -> {
-			try {
-				// Load headers
-				long start = now();
-				Collection<H> headers = loadHeaders();
-				logDuration(LOG, "Loading headers", start);
-
-				// Load bodies into cache
-				start = now();
-				for (H header : headers) {
-					if (!textCache.containsKey(header.getId())) {
-						textCache.put(header.getId(),
-								loadMessageText(header));
-					}
-				}
-				logDuration(LOG, "Loading bodies", start);
-
-				// Build and hand over items
-				handler.onResult(buildItems(headers));
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				handler.onException(e);
-			}
-		});
-	}
-
-	@DatabaseExecutor
-	protected abstract Collection<H> loadHeaders() throws DbException;
-
-	@DatabaseExecutor
-	protected abstract String loadMessageText(H header) throws DbException;
-
 	@Override
 	public void markItemRead(I item) {
 		markItemsRead(Collections.singletonList(item));
@@ -207,19 +169,6 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 	@DatabaseExecutor
 	protected abstract H addLocalMessage(M message) throws DbException;
 
-	private ThreadItemList<I> buildItems(Collection<H> headers)
-			throws DbException {
-		ThreadItemList<I> items = new ThreadItemListImpl<>();
-		for (H h : headers) {
-			items.add(buildItem(h, textCache.get(h.getId())));
-		}
-		MessageId msgId = messageTracker.loadStoredMessageId(groupId);
-		if (LOG.isLoggable(INFO))
-			LOG.info("Loaded last top visible message id " + msgId);
-		items.setFirstVisibleId(msgId);
-		return items;
-	}
-
 	protected abstract I buildItem(H header, String text);
 
 	protected GroupId getGroupId() {

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListViewModel.java

@@ -4,6 +4,8 @@ import android.app.Application;
 
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 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;
@@ -12,34 +14,51 @@ 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.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.Clock;
 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.client.NamedGroup;
+import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.client.PostHeader;
 
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import androidx.annotation.CallSuper;
+import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 
+import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.now;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public abstract class ThreadListViewModel<G extends NamedGroup, I extends ThreadItem>
+public abstract class ThreadListViewModel<I extends ThreadItem> extends DbViewModel
-		extends DbViewModel implements EventListener {
+		implements EventListener {
 
 	private static final Logger LOG =
 			getLogger(ThreadListViewModel.class.getName());
 
-
 	protected final IdentityManager identityManager;
 	protected final AndroidNotificationManager notificationManager;
 	protected final Executor cryptoExecutor;
 	protected final Clock clock;
+	private final MessageTracker messageTracker;
 	private final EventBus eventBus;
 
+	private final Map<MessageId, String> textCache = new ConcurrentHashMap<>();
+	private final MutableLiveData<LiveResult<List<I>>> items =
+			new MutableLiveData<>();
+
 	protected volatile GroupId groupId;
 
 	public ThreadListViewModel(Application application,
@@ -51,12 +70,14 @@ public abstract class ThreadListViewModel<G extends NamedGroup, I extends Thread
 			AndroidNotificationManager notificationManager,
 			@CryptoExecutor Executor cryptoExecutor,
 			Clock clock,
+			MessageTracker messageTracker,
 			EventBus eventBus) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.identityManager = identityManager;
 		this.notificationManager = notificationManager;
 		this.cryptoExecutor = cryptoExecutor;
 		this.clock = clock;
+		this.messageTracker = messageTracker;
 		this.eventBus = eventBus;
 		this.eventBus.addListener(this);
 	}
@@ -74,6 +95,52 @@ public abstract class ThreadListViewModel<G extends NamedGroup, I extends Thread
 	@CallSuper
 	public void setGroupId(GroupId groupId) {
 		this.groupId = groupId;
+		loadItems();
+	}
+
+	public abstract void loadItems();
+
+	@UiThread
+	protected void setItems(LiveResult<List<I>> items) {
+		this.items.setValue(items);
+	}
+
+	@DatabaseExecutor
+	protected <H extends PostHeader> List<I> buildItems(
+			Transaction txn, Collection<H> headers, ItemGetter<H, I> itemGetter)
+			throws DbException {
+		long start = now();
+		ThreadItemList<I> items = new ThreadItemListImpl<>();
+		for (H header : headers) {
+			MessageId id = header.getId();
+			String text = textCache.get(header.getId());
+			if (text == null) {
+				text = loadMessageText(txn, header);
+				textCache.put(id, text);
+			}
+			items.add(itemGetter.getItem(header, text));
+		}
+		logDuration(LOG, "Loading bodies and creating items", start);
+
+		MessageId msgId = messageTracker.loadStoredMessageId(txn, groupId);
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Loaded last top visible message id " + msgId);
+		}
+		// TODO store this elsewhere
+		items.setFirstVisibleId(msgId);
+		return items;
+	}
+
+	@DatabaseExecutor
+	protected abstract String loadMessageText(Transaction txn,
+			PostHeader header) throws DbException;
+
+	LiveData<LiveResult<List<I>>> getItems() {
+		return items;
+	}
+
+	public interface ItemGetter<H extends PostHeader, I> {
+		I getItem(H header, String text);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadScrollListener.java

@@ -20,11 +20,11 @@ class ThreadScrollListener<I extends ThreadItem>
 	private static final Logger LOG =
 			getLogger(ThreadScrollListener.class.getName());
 
-	private final ThreadListController<?, I> controller;
+	private final ThreadListController<I> controller;
 	private final UnreadMessageButton upButton, downButton;
 
 	ThreadScrollListener(ThreadItemAdapter<I> adapter,
-			ThreadListController<?, I> controller,
+			ThreadListController<I> controller,
 			UnreadMessageButton upButton,
 			UnreadMessageButton downButton) {
 		super(adapter);

briar-api/src/main/java/org/briarproject/briar/api/client/MessageTree.java

@@ -4,7 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 
 import java.util.Collection;
-import java.util.Comparator;
+import java.util.List;
 
 import javax.annotation.Nullable;
 
@@ -13,14 +13,15 @@ public interface MessageTree<T extends MessageTree.MessageNode> {
 
 	void add(Collection<T> nodes);
 
+	@Deprecated
 	void add(T node);
 
-	void setComparator(Comparator<T> comparator);
+	@Deprecated
-
 	void clear();
 
-	Collection<T> depthFirstOrder();
+	List<T> depthFirstOrder();
 
+	@Deprecated
 	boolean contains(MessageId m);
 
 	@NotNullByDefault

briar-core/src/main/java/org/briarproject/briar/client/MessageTreeImpl.java

@@ -30,9 +30,14 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 	private final List<List<T>> unsortedLists = new ArrayList<>();
 
 	@SuppressWarnings("UseCompareMethod")
-	private Comparator<T> comparator = (o1, o2) ->
+	private final Comparator<T> comparator = (o1, o2) ->
 			Long.valueOf(o1.getTimestamp()).compareTo(o2.getTimestamp());
 
+	public MessageTreeImpl(Collection<T> collection) {
+		super();
+		add(collection);
+	}
+
 	@Override
 	public synchronized void clear() {
 		roots.clear();
@@ -79,6 +84,7 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 	@GuardedBy("this")
 	private void sortUnsorted() {
 		for (List<T> list : unsortedLists) {
+			//noinspection Java8ListSort
 			Collections.sort(list, comparator);
 		}
 		unsortedLists.clear();
@@ -95,17 +101,7 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 	}
 
 	@Override
-	public synchronized void setComparator(Comparator<T> comparator) {
+	public synchronized List<T> depthFirstOrder() {
-		this.comparator = comparator;
-		// Sort all lists with the new comparator
-		Collections.sort(roots, comparator);
-		for (Map.Entry<MessageId, List<T>> entry : nodeMap.entrySet()) {
-			Collections.sort(entry.getValue(), comparator);
-		}
-	}
-
-	@Override
-	public synchronized Collection<T> depthFirstOrder() {
 		List<T> orderedList = new ArrayList<>();
 		for (T root : roots) {
 			traverse(orderedList, root, 0);