thread list: fix redundant load and dissolved dialog showing again after screen rotation

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

@@ -79,7 +79,7 @@ public class GroupActivity extends
 
 		// start with group disabled and enable when not dissolved
 		setGroupEnabled(false);
-		viewModel.isDissolved().observe(this, dissolved -> {
+		viewModel.isDissolved().observeEvent(this, dissolved -> {
 			setGroupEnabled(!dissolved);
 			if (dissolved) onGroupDissolved();
 		});
@@ -153,7 +153,7 @@ public class GroupActivity extends
 
 	@Override
 	public void onReplyClick(GroupMessageItem item) {
-		Boolean isDissolved = viewModel.isDissolved().getValue();
+		Boolean isDissolved = viewModel.isDissolved().getLastValue();
 		if (isDissolved != null && !isDissolved) super.onReplyClick(item);
 	}
 

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

@@ -22,6 +22,8 @@ import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.sharing.SharingController;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.MessageTracker.GroupCount;
@@ -70,8 +72,8 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 	private final MutableLiveData<PrivateGroup> privateGroup =
 			new MutableLiveData<>();
 	private final MutableLiveData<Boolean> isCreator = new MutableLiveData<>();
-	private final MutableLiveData<Boolean> isDissolved =
-			new MutableLiveData<>();
+	private final MutableLiveEvent<Boolean> isDissolved =
+			new MutableLiveEvent<>();
 
 	@Inject
 	GroupViewModel(Application application,
@@ -128,7 +130,7 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 		} else if (e instanceof GroupDissolvedEvent) {
 			GroupDissolvedEvent g = (GroupDissolvedEvent) e;
 			if (g.getGroupId().equals(groupId)) {
-				isDissolved.setValue(true);
+				isDissolved.setEvent(true);
 			}
 		} else {
 			super.eventOccurred(e);
@@ -136,8 +138,8 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 	}
 
 	@Override
-	public void setGroupId(GroupId groupId) {
-		super.setGroupId(groupId);
+	protected void performInitialLoad() {
+		super.performInitialLoad();
 		loadPrivateGroup(groupId);
 	}
 
@@ -163,7 +165,7 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 		loadList(txn -> {
 			// check first if group is dissolved
 			isDissolved
-					.postValue(privateGroupManager.isDissolved(txn, groupId));
+					.postEvent(privateGroupManager.isDissolved(txn, groupId));
 			// now continue to load the items
 			long start = now();
 			List<GroupMessageHeader> headers =
@@ -275,7 +277,7 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 		return isCreator;
 	}
 
-	LiveData<Boolean> isDissolved() {
+	LiveEvent<Boolean> isDissolved() {
 		return isDissolved;
 	}
 

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

@@ -115,9 +115,14 @@ public abstract class ThreadListViewModel<I extends ThreadItem>
 	 * Needs to be called right after initialization,
 	 * before calling any other methods.
 	 */
-	@CallSuper
-	public void setGroupId(GroupId groupId) {
+	public final void setGroupId(GroupId groupId) {
+		boolean needsInitialLoad = this.groupId == null;
 		this.groupId = groupId;
+		if (needsInitialLoad) performInitialLoad();
+	}
+
+	@CallSuper
+	protected void performInitialLoad() {
 		loadStoredMessageId();
 		loadItems();
 		loadSharingContacts();

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

@@ -39,6 +39,17 @@ public class LiveEvent<T> extends LiveData<LiveEvent.ConsumableEvent<T>> {
 		super.observeForever(observer);
 	}
 
+	/**
+	 * Returns the last value of the event (even if already consumed)
+	 * or null if there hasn't been any value so far.
+	 */
+	@Nullable
+	public T getLastValue() {
+		ConsumableEvent<T> event = getValue();
+		if (event == null) return null;
+		return event.content;
+	}
+
 	static class ConsumableEvent<T> {
 
 		private final T content;