[android] use ScrollListener to mark messages read in private conversation

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -47,7 +47,6 @@ import org.briarproject.bramble.api.plugin.ConnectionRegistry;
 import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
 import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
 import org.briarproject.bramble.api.settings.SettingsManager;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
@@ -256,6 +255,9 @@ public class ConversationActivity extends BriarActivity
 		list.setLayoutManager(layoutManager);
 		list.setAdapter(adapter);
 		list.setEmptyText(getString(R.string.no_private_messages));
+		ConversationScrollListener scrollListener =
+				new ConversationScrollListener(adapter, viewModel);
+		list.getRecyclerView().addOnScrollListener(scrollListener);
 
 		textInputView = findViewById(R.id.text_input_container);
 		if (FEATURE_FLAG_IMAGE_ATTACHMENTS) {
@@ -787,23 +789,6 @@ public class ConversationActivity extends BriarActivity
 				.show();
 	}
 
-	@Override
-	public void onItemVisible(ConversationItem item) {
-		if (!item.isRead()) markMessageRead(item.getGroupId(), item.getId());
-	}
-
-	private void markMessageRead(GroupId g, MessageId m) {
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				messagingManager.setReadFlag(g, m, true);
-				logDuration(LOG, "Marking read", start);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
-	}
-
 	@UiThread
 	@Override
 	public void respondToRequest(ConversationRequestItem item, boolean accept) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationAdapter.java

@@ -14,12 +14,14 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.util.BriarAdapter;
+import org.briarproject.briar.android.util.ItemReturningAdapter;
 
 import javax.annotation.Nullable;
 
 @NotNullByDefault
 class ConversationAdapter
-		extends BriarAdapter<ConversationItem, ConversationItemViewHolder> {
+		extends BriarAdapter<ConversationItem, ConversationItemViewHolder>
+		implements ItemReturningAdapter<ConversationItem> {
 
 	private ConversationListener listener;
 	private final RecycledViewPool imageViewPool;
@@ -69,7 +71,6 @@ class ConversationAdapter
 	public void onBindViewHolder(ConversationItemViewHolder ui, int position) {
 		ConversationItem item = items.get(position);
 		ui.bind(item);
-		listener.onItemVisible(item);
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationItem.java

@@ -69,6 +69,10 @@ abstract class ConversationItem {
 		return read;
 	}
 
+	void markRead() {
+		read = true;
+	}
+
 	/**
 	 * Only useful for outgoing messages.
 	 */

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationListener.java

@@ -9,8 +9,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 @NotNullByDefault
 interface ConversationListener {
 
-	void onItemVisible(ConversationItem item);
-
 	void respondToRequest(ConversationRequestItem item, boolean accept);
 
 	void openRequestedShareable(ConversationRequestItem item);

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationScrollListener.java

@@ -0,0 +1,26 @@
+package org.briarproject.briar.android.conversation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.view.BriarRecyclerViewScrollListener;
+
+@NotNullByDefault
+class ConversationScrollListener extends
+		BriarRecyclerViewScrollListener<ConversationAdapter, ConversationItem> {
+
+	private final ConversationViewModel viewModel;
+
+	protected ConversationScrollListener(ConversationAdapter adapter,
+			ConversationViewModel viewModel) {
+		super(adapter);
+		this.viewModel = viewModel;
+	}
+
+	@Override
+	protected void onNewItemVisible(ConversationItem item) {
+		if (!item.isRead()) {
+			viewModel.markMessageRead(item.getGroupId(), item.getId());
+			item.markRead();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -26,6 +26,7 @@ import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.util.UiUtils;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
@@ -150,6 +151,18 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
+	void markMessageRead(GroupId g, MessageId m) {
+		dbExecutor.execute(() -> {
+			try {
+				long start = now();
+				messagingManager.setReadFlag(g, m, true);
+				logDuration(LOG, "Marking read", start);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
 	void setContactAlias(String alias) {
 		dbExecutor.execute(() -> {
 			try {