Dynamic previous/next navigation

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -279,7 +279,22 @@ public class FragmentMessages extends FragmentBase {
 
         rvMessage.setAdapter(adapter);
 
-        if (viewType != AdapterMessage.ViewType.THREAD) {
+        if (viewType == AdapterMessage.ViewType.THREAD) {
+            ViewModelMessages model = ViewModelProviders.of(getActivity()).get(ViewModelMessages.class);
+            model.observePrevNext(getViewLifecycleOwner(), thread, new ViewModelMessages.IPrevNext() {
+                @Override
+                public void onPrevious(Long id) {
+                    bottom_navigation.getMenu().findItem(R.id.action_prev).setIntent(new Intent().putExtra("id", id));
+                    bottom_navigation.getMenu().findItem(R.id.action_prev).setEnabled(id != null);
+                }
+
+                @Override
+                public void onNext(Long id) {
+                    bottom_navigation.getMenu().findItem(R.id.action_next).setIntent(new Intent().putExtra("id", id));
+                    bottom_navigation.getMenu().findItem(R.id.action_next).setEnabled(id != null);
+                }
+            });
+        } else {
             final SelectionPredicateMessage predicate = new SelectionPredicateMessage(rvMessage);
 
             selectionTracker = new SelectionTracker.Builder<>(
@@ -341,11 +356,11 @@ public class FragmentMessages extends FragmentBase {
                         return true;
 
                     case R.id.action_prev:
-                        navigate(false);
+                        navigate(menuItem.getIntent().getLongExtra("id", -1));
                         return true;
 
                     case R.id.action_next:
-                        navigate(true);
+                        navigate(menuItem.getIntent().getLongExtra("id", -1));
                         return true;
 
                     default:
@@ -393,6 +408,8 @@ public class FragmentMessages extends FragmentBase {
         // Initialize
         swipeRefresh.setEnabled(pull);
         tvNoEmail.setVisibility(View.GONE);
+        bottom_navigation.getMenu().findItem(R.id.action_prev).setEnabled(false);
+        bottom_navigation.getMenu().findItem(R.id.action_next).setEnabled(false);
         bottom_navigation.setVisibility(View.GONE);
         grpReady.setVisibility(View.GONE);
         pbWait.setVisibility(View.VISIBLE);
@@ -2015,24 +2032,41 @@ public class FragmentMessages extends FragmentBase {
     private void handleAutoClose() {
         if (autoclose)
             finish();
-        else if (autonext)
-            navigate(true);
+        else if (autonext) {
+            Intent intent = bottom_navigation.getMenu().findItem(R.id.action_next).getIntent();
+            Long id = (intent == null ? null : intent.getLongExtra("id", -1));
+            if (id == null || id < 0)
+                finish();
+            else
+                navigate(id);
+        }
     }
 
-    private void navigate(boolean next) {
-        ViewModelMessages model = ViewModelProviders.of(getActivity()).get(ViewModelMessages.class);
-        ViewModelMessages.Target target = model.getPrevNext(thread)[next ? 1 : 0];
+    private void navigate(long id) {
+        Bundle args = new Bundle();
+        args.putLong("id", id);
+        new SimpleTask<EntityMessage>() {
+            @Override
+            protected EntityMessage onExecute(Context context, Bundle args) {
+                long id = args.getLong("id");
+                return DB.getInstance(context).message().getMessage(id);
+            }
 
-        if (target == null)
-            finish();
-        else {
-            LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(getContext());
-            lbm.sendBroadcast(
-                    new Intent(ActivityView.ACTION_VIEW_THREAD)
-                            .putExtra("account", target.account)
-                            .putExtra("thread", target.thread)
-                            .putExtra("id", target.id));
-        }
+            @Override
+            protected void onExecuted(Bundle args, EntityMessage message) {
+                LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(getContext());
+                lbm.sendBroadcast(
+                        new Intent(ActivityView.ACTION_VIEW_THREAD)
+                                .putExtra("account", message.account)
+                                .putExtra("thread", message.thread)
+                                .putExtra("id", message.id));
+            }
+
+            @Override
+            protected void onException(Bundle args, Throwable ex) {
+                Helper.unexpectedError(getContext(), getViewLifecycleOwner(), ex);
+            }
+        }.execute(this, args, "messages:navigate");
     }
 
     private void moveAsk(final ArrayList<MessageTarget> result) {

app/src/main/java/eu/faircode/email/ViewModelMessages.java

@@ -81,47 +81,49 @@ public class ViewModelMessages extends ViewModel {
         messages.clear();
     }
 
-    Target[] getPrevNext(String thread) {
+    void observePrevNext(LifecycleOwner owner, final String thread, final IPrevNext intf) {
         LiveData<PagedList<TupleMessageEx>> list = messages.get(false);
-        if (list == null || list.getValue() == null || list.getValue().size() == 0)
-            return new Target[]{null, null};
-
-        boolean found = false;
-        TupleMessageEx prev = null;
-        TupleMessageEx next = null;
-        for (int i = 0; i < list.getValue().size(); i++) {
-            TupleMessageEx item = list.getValue().get(i);
-            if (item == null)
-                continue;
-            if (found) {
-                prev = item;
-                break;
-            }
-            if (thread.equals(item.thread)) {
-                found = true;
-                list.getValue().loadAround(i);
-            } else
-                next = item;
-        }
-        if (!found)
-            return new Target[]{null, null};
+        if (list == null)
+            return;
 
-        return new Target[]{
-                prev == null ? null : new Target(prev.account, prev.thread, prev.id, prev.ui_found),
-                next == null ? null : new Target(next.account, next.thread, next.id, next.ui_found)};
+        list.observe(owner, new Observer<PagedList<TupleMessageEx>>() {
+            @Override
+            public void onChanged(PagedList<TupleMessageEx> list) {
+                boolean load = false;
+                for (int pos = 0; pos < list.size(); pos++) {
+                    TupleMessageEx item = list.get(pos);
+                    if (item != null && thread.equals(item.thread)) {
+                        if (pos - 1 >= 0) {
+                            TupleMessageEx next = list.get(pos - 1);
+                            if (next == null)
+                                load = true;
+                            else
+                                intf.onNext(next.id);
+                        } else
+                            intf.onNext(null);
+
+                        if (pos + 1 <= list.size()) {
+                            TupleMessageEx prev = list.get(pos + 1);
+                            if (prev == null)
+                                load = true;
+                            else
+                                intf.onPrevious(prev.id);
+                        } else
+                            intf.onPrevious(null);
+
+                        if (load)
+                            list.loadAround(pos);
+
+                        break;
+                    }
+                }
+            }
+        });
     }
 
-    class Target {
-        long account;
-        String thread;
-        long id;
-        boolean found;
-
-        Target(long account, String thread, long id, boolean found) {
-            this.account = account;
-            this.thread = thread;
-            this.id = id;
-            this.found = found;
-        }
+    interface IPrevNext {
+        void onPrevious(Long id);
+
+        void onNext(Long id);
     }
 }