Batch notify new messages

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

@@ -89,6 +89,11 @@ public interface DaoFolder {
             " AND folder.type = '" + EntityFolder.DRAFTS + "'")
     LiveData<EntityFolder> livePrimaryDrafts();
 
+    @Query("SELECT COUNT(id) FROM folder" +
+            " WHERE sync_state = 'syncing'" +
+            " AND folder.type <> '" + EntityFolder.OUTBOX + "'")
+    LiveData<Integer> liveSynchronizing();
+
     @Query("SELECT folder.*" +
             ", account.name AS accountName, account.color AS accountColor, account.state AS accountState" +
             ", COUNT(message.id) AS messages" +

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

@@ -128,7 +128,20 @@ public class ServiceSynchronize extends LifecycleService {
             }
         });
 
-        db.message().liveUnseenNotify().observe(this, new Observer<List<TupleMessageEx>>() {
+        final TwoStateOwner cowner = new TwoStateOwner(this);
+
+        db.folder().liveSynchronizing().observe(this, new Observer<Integer>() {
+            @Override
+            public void onChanged(Integer count) {
+                Log.i("Synchronizing folders=" + count);
+                if (count == 0)
+                    cowner.start();
+                else
+                    cowner.stop();
+            }
+        });
+
+        db.message().liveUnseenNotify().observe(cowner, new Observer<List<TupleMessageEx>>() {
             @Override
             public void onChanged(List<TupleMessageEx> messages) {
                 Core.notifyMessages(ServiceSynchronize.this, messages);