list position save and restore now implemented for threaded lists

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

@@ -32,6 +32,7 @@ import org.briarproject.briar.api.android.ScreenFilterMonitor;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPostFactory;
 import org.briarproject.briar.api.blog.BlogSharingManager;
+import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.feed.FeedManager;
 import org.briarproject.briar.api.forum.ForumManager;
 import org.briarproject.briar.api.forum.ForumSharingManager;
@@ -78,6 +79,8 @@ public interface AndroidComponent
 	@DatabaseExecutor
 	Executor databaseExecutor();
 
+	MessageTracker messageTracker();
+
 	LifecycleManager lifecycleManager();
 
 	IdentityManager identityManager();

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

 package org.briarproject.briar.android.threaded;
 
+import android.os.Handler;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
 import android.support.v7.widget.LinearLayoutManager;
@@ -26,6 +27,7 @@ public class ThreadItemAdapter<I extends ThreadItem>
 	protected final NestedTreeList<I> items = new NestedTreeList<>();
 	private final ThreadItemListener<I> listener;
 	private final LinearLayoutManager layoutManager;
+	private final Handler handler = new Handler();
 
 	private volatile int revision = 0;
 
@@ -64,6 +66,31 @@ public class ThreadItemAdapter<I extends ThreadItem>
 		revision++;
 	}
 
+	void setBottomItem(MessageId messageId) {
+		if (messageId != null) {
+			int pos = 0;
+			for (I item : items) {
+				if (item.getId().equals(messageId)) {
+					scrollToPosition(pos);
+					break;
+
+				}
+				pos++;
+			}
+		}
+	}
+
+	private void scrollToPosition(final int pos) {
+		// Post call ensures that the list scrolls AFTER it has been propagated
+		// and the layout has been calculated.
+		handler.post(new Runnable() {
+			@Override
+			public void run() {
+				layoutManager.scrollToPosition(pos);
+			}
+		});
+	}
+
 	public void setItems(Collection<I> items) {
 		this.items.clear();
 		this.items.addAll(items);

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

+package org.briarproject.briar.android.threaded;
+
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.List;
+
+import javax.annotation.Nullable;
+
+public interface ThreadItemList<I extends ThreadItem> extends List<I> {
+
+	@Nullable
+	MessageId getBottomVisibleItemId();
+
+	void setBottomVisibleItemId(@Nullable MessageId bottomVisibleItemId);
+}

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

+package org.briarproject.briar.android.threaded;
+
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.ArrayList;
+
+import javax.annotation.Nullable;
+
+public class ThreadItemListImpl<I extends ThreadItem> extends ArrayList<I>
+		implements ThreadItemList<I> {
+
+	private MessageId bottomVisibleItemId;
+
+	@Override
+	public MessageId getBottomVisibleItemId() {
+		return bottomVisibleItemId;
+	}
+
+	public void setBottomVisibleItemId(@Nullable MessageId bottomVisibleItemId) {
+		this.bottomVisibleItemId = bottomVisibleItemId;
+	}
+}

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

@@ -26,6 +26,7 @@ import org.briarproject.briar.android.controller.SharingController;
 import org.briarproject.briar.android.controller.SharingController.SharingListener;
 import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.briar.android.threaded.ThreadItemAdapter.ThreadItemListener;
+import org.briarproject.briar.android.threaded.ThreadListController.ThreadListDataSource;
 import org.briarproject.briar.android.threaded.ThreadListController.ThreadListListener;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.view.TextInputView;
@@ -51,7 +52,7 @@ import static org.briarproject.briar.android.threaded.ThreadItemAdapter.UnreadCo
 public abstract class ThreadListActivity<G extends NamedGroup, A extends ThreadItemAdapter<I>, I extends ThreadItem, H extends PostHeader>
 		extends BriarActivity
 		implements ThreadListListener<H>, TextInputListener, SharingListener,
-		ThreadItemListener<I> {
+		ThreadItemListener<I>, ThreadListDataSource {
 
 	protected static final String KEY_REPLY_ID = "replyId";
 
@@ -68,6 +69,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, A extends ThreadI
 	private MessageId replyId;
 
 	protected abstract ThreadListController<G, I, H> getController();
+
 	@Inject
 	protected SharingController sharingController;
 
@@ -104,6 +106,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, A extends ThreadI
 							updateUnreadCount();
 						}
 					}
+
 					@Override
 					public void onScrollStateChanged(RecyclerView recyclerView,
 							int newState) {
@@ -144,6 +147,16 @@ public abstract class ThreadListActivity<G extends NamedGroup, A extends ThreadI
 		loadSharingContacts();
 	}
 
+	@Override
+	public MessageId getBottomVisibleMessageId() {
+		if (layoutManager != null && adapter != null) {
+			int position =
+					layoutManager.findLastCompletelyVisibleItemPosition();
+			return adapter.getItemAt(position).getId();
+		}
+		return null;
+	}
+
 	protected abstract A createAdapter(LinearLayoutManager layoutManager);
 
 	protected void loadNamedGroup() {
@@ -167,15 +180,18 @@ public abstract class ThreadListActivity<G extends NamedGroup, A extends ThreadI
 	protected void loadItems() {
 		final int revision = adapter.getRevision();
 		getController().loadItems(
-				new UiResultExceptionHandler<Collection<I>, DbException>(this) {
+				new UiResultExceptionHandler<ThreadItemList<I>, DbException>(
+						this) {
 					@Override
-					public void onResultUi(Collection<I> items) {
+					public void onResultUi(ThreadItemList<I> items) {
 						if (revision == adapter.getRevision()) {
 							adapter.incrementRevision();
 							if (items.isEmpty()) {
 								list.showData();
 							} else {
 								adapter.setItems(items);
+								adapter.setBottomItem(
+										items.getBottomVisibleItemId());
 								list.showData();
 								updateTextInput(replyId);
 							}

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

@@ -6,6 +6,7 @@ import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.DestroyableContext;
 import org.briarproject.briar.android.controller.ActivityLifecycleController;
 import org.briarproject.briar.android.controller.handler.ExceptionHandler;
@@ -30,7 +31,7 @@ public interface ThreadListController<G extends NamedGroup, I extends ThreadItem
 
 	void loadItem(H header, ResultExceptionHandler<I, DbException> handler);
 
-	void loadItems(ResultExceptionHandler<Collection<I>, DbException> handler);
+	void loadItems(ResultExceptionHandler<ThreadItemList<I>, DbException> handler);
 
 	void markItemRead(I item);
 
@@ -52,4 +53,10 @@ public interface ThreadListController<G extends NamedGroup, I extends ThreadItem
 		void onInvitationAccepted(ContactId c);
 	}
 
+	interface ThreadListDataSource {
+
+		@UiThread @Nullable
+		MessageId getBottomVisibleMessageId();
+	}
+
 }

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

@@ -22,19 +22,20 @@ import org.briarproject.briar.android.controller.handler.ExceptionHandler;
 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;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import javax.inject.Inject;
+
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 
@@ -56,6 +57,9 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 	protected final Executor cryptoExecutor;
 	protected final Clock clock;
 	protected volatile L listener;
+	@Inject
+	MessageTracker messageTracker;
+	private ThreadListDataSource source;
 
 	protected ThreadListControllerImpl(@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager, IdentityManager identityManager,
@@ -79,6 +83,13 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 	@Override
 	public void onActivityCreate(Activity activity) {
 		listener = (L) activity;
+		if (activity instanceof ThreadListDataSource) {
+			source = (ThreadListDataSource) activity;
+		} else {
+			throw new ClassCastException(
+					"Activity " + activity.getClass().getSimpleName() +
+							" must implement ThreadListDataSource");
+		}
 	}
 
 	@CallSuper
@@ -97,6 +108,13 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 
 	@Override
 	public void onActivityDestroy() {
+		try {
+			messageTracker
+					.storeMessageId(groupId,
+							source.getBottomVisibleMessageId());
+		} catch (DbException e) {
+			e.printStackTrace();
+		}
 	}
 
 	@CallSuper
@@ -144,7 +162,7 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 
 	@Override
 	public void loadItems(
-			final ResultExceptionHandler<Collection<I>, DbException> handler) {
+			final ResultExceptionHandler<ThreadItemList<I>, DbException> handler) {
 		checkGroupId();
 		runOnDbThread(new Runnable() {
 			@Override
@@ -293,11 +311,19 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 	@DatabaseExecutor
 	protected abstract void deleteNamedGroup(G groupItem) throws DbException;
 
-	private List<I> buildItems(Collection<H> headers) {
-		List<I> items = new ArrayList<>();
+	private ThreadItemList<I> buildItems(Collection<H> headers) {
+		ThreadItemList<I> items = new ThreadItemListImpl<>();
 		for (H h : headers) {
 			items.add(buildItem(h, bodyCache.get(h.getId())));
 		}
+		try {
+			MessageId msgId = messageTracker.loadStoredMessageId(groupId);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Loaded last top visible message id " + msgId);
+			items.setBottomVisibleItemId(msgId);
+		} catch (DbException e) {
+			e.printStackTrace();
+		}
 		return items;
 	}
 

briar-android/src/test/java/org/briarproject/briar/android/forum/ForumActivityTest.java

@@ -13,6 +13,8 @@ import org.briarproject.briar.BuildConfig;
 import org.briarproject.briar.android.TestBriarApplication;
 import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.briar.android.threaded.ThreadItemAdapter;
+import org.briarproject.briar.android.threaded.ThreadItemList;
+import org.briarproject.briar.android.threaded.ThreadItemListImpl;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -23,10 +25,7 @@ import org.robolectric.Robolectric;
 import org.robolectric.RobolectricGradleTestRunner;
 import org.robolectric.annotation.Config;
 
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collection;
-import java.util.List;
 
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertTrue;
@@ -81,7 +80,7 @@ public class ForumActivityTest {
 
 	private TestForumActivity forumActivity;
 	@Captor
-	private ArgumentCaptor<UiResultExceptionHandler<Collection<ForumItem>, DbException>>
+	private ArgumentCaptor<UiResultExceptionHandler<ThreadItemList<ForumItem>, DbException>>
 			rc;
 
 	@Before
@@ -93,7 +92,7 @@ public class ForumActivityTest {
 				.withIntent(intent).create().resume().get();
 	}
 
-	private List<ForumItem> getDummyData() {
+	private ThreadItemList<ForumItem> getDummyData() {
 		ForumItem[] forumItems = new ForumItem[6];
 		for (int i = 0; i < forumItems.length; i++) {
 			AuthorId authorId = new AuthorId(TestUtils.getRandomId());
@@ -103,13 +102,15 @@ public class ForumActivityTest {
 					AUTHORS[i], System.currentTimeMillis(), author, UNKNOWN);
 			forumItems[i].setLevel(LEVELS[i]);
 		}
-		return new ArrayList<>(Arrays.asList(forumItems));
+		ThreadItemList<ForumItem> list = new ThreadItemListImpl<>();
+		list.addAll(Arrays.asList(forumItems));
+		return list;
 	}
 
 	@Test
 	public void testNestedEntries() {
 		ForumController mc = forumActivity.getController();
-		List<ForumItem> dummyData = getDummyData();
+		ThreadItemList<ForumItem> dummyData = getDummyData();
 		verify(mc, times(1)).loadItems(rc.capture());
 		rc.getValue().onResult(dummyData);
 		ThreadItemAdapter<ForumItem> adapter = forumActivity.getAdapter();

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

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 
+import javax.annotation.Nullable;
+
 @NotNullByDefault
 public interface MessageTracker {
 
@@ -38,6 +40,19 @@ public interface MessageTracker {
 	void trackMessage(Transaction txn, GroupId g, long timestamp, boolean read)
 			throws DbException;
 
+	/**
+	 *  Loads the stored message id for the respective group id or returns null
+	 *  if none is available.
+	 */
+	@Nullable
+	MessageId loadStoredMessageId(GroupId g) throws DbException;
+
+	/**
+	 * Stores the message id for the respective group id. Exactly one message id
+	 * can be stored for any group id at any time, older values are overwritten.
+	 */
+	void storeMessageId(GroupId g, MessageId m) throws DbException;
+
 	/**
 	 * Marks a message as read or unread and updates the group count.
 	 */

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

@@ -2,6 +2,7 @@ package org.briarproject.briar.client;
 
 public interface MessageTrackerConstants {
 
+	String GROUP_KEY_STORED_MESSAGE_ID = "storedMessageId";
 	String GROUP_KEY_MSG_COUNT = "messageCount";
 	String GROUP_KEY_UNREAD_COUNT = "unreadCount";
 	String GROUP_KEY_LATEST_MSG = "latestMessageTime";

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

@@ -13,11 +13,13 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.MessageTracker;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static org.briarproject.briar.client.MessageTrackerConstants.GROUP_KEY_LATEST_MSG;
 import static org.briarproject.briar.client.MessageTrackerConstants.GROUP_KEY_MSG_COUNT;
+import static org.briarproject.briar.client.MessageTrackerConstants.GROUP_KEY_STORED_MESSAGE_ID;
 import static org.briarproject.briar.client.MessageTrackerConstants.GROUP_KEY_UNREAD_COUNT;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 
@@ -57,6 +59,30 @@ class MessageTrackerImpl implements MessageTracker {
 				latestMsgTime));
 	}
 
+	@Nullable
+	@Override
+	public MessageId loadStoredMessageId(GroupId g) throws DbException {
+		try {
+			BdfDictionary d = clientHelper.getGroupMetadataAsDictionary(g);
+			byte[] msgBytes = d.getOptionalRaw(GROUP_KEY_STORED_MESSAGE_ID);
+			return msgBytes != null? new MessageId(msgBytes) : null;
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	@Override
+	public void storeMessageId(GroupId g, MessageId m) throws DbException {
+		BdfDictionary d = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_STORED_MESSAGE_ID, m)
+		);
+		try {
+			clientHelper.mergeGroupMetadata(g, d);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public GroupCount getGroupCount(GroupId g) throws DbException {
 		GroupCount count;

briar-core/src/test/java/org/briarproject/briar/forum/ForumManagerTest.java

 package org.briarproject.briar.forum;
 
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.test.TestDatabaseModule;
+import org.briarproject.bramble.test.TestUtils;
 import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumManager;
 import org.briarproject.briar.api.forum.ForumPost;
@@ -10,6 +13,7 @@ import org.briarproject.briar.api.forum.ForumSharingManager;
 import org.briarproject.briar.test.BriarIntegrationTest;
 import org.briarproject.briar.test.BriarIntegrationTestComponent;
 import org.briarproject.briar.test.DaggerBriarIntegrationTestComponent;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -223,4 +227,18 @@ public class ForumManagerTest
 		assertEquals(1, forumManager1.getPostHeaders(g1).size());
 	}
 
+	@Test
+	public void testMessageStoreAndLoad() {
+		MessageId msgId = new MessageId(TestUtils.getRandomId());
+		MessageId loadedId = null;
+		try {
+			messageTracker0.storeMessageId(groupId0, msgId);
+			loadedId = messageTracker0.loadStoredMessageId(groupId0);
+		} catch (DbException e) {
+			e.printStackTrace();
+		}
+		Assert.assertNotNull(loadedId);
+		Assert.assertTrue(msgId.equals(loadedId));
+	}
+
 }