Simplify operations watcher

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

@@ -80,7 +80,6 @@ import androidx.annotation.Nullable;
 import androidx.core.app.NotificationCompat;
 import androidx.core.content.ContextCompat;
 import androidx.lifecycle.LifecycleService;
-import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
 
 import static android.os.Process.THREAD_PRIORITY_BACKGROUND;
@@ -493,7 +492,7 @@ public class ServiceSynchronize extends LifecycleService {
 
                 final Map<EntityFolder, Folder> folders = new HashMap<>();
                 List<Thread> idlers = new ArrayList<>();
-                List<Handler> handlers = new ArrayList<>();
+                List<TwoStateOwner> owners = new ArrayList<>();
                 try {
                     // Listen for store events
                     istore.addStoreListener(new StoreListener() {
@@ -815,29 +814,14 @@ public class ServiceSynchronize extends LifecycleService {
                         } else
                             folders.put(folder, null);
 
-                        // Observe operations
-                        Handler handler = new Handler(getMainLooper()) {
-                            private List<Long> waiting = new ArrayList<>();
-                            private List<Long> handling = new ArrayList<>();
-                            private LiveData<List<EntityOperation>> liveOperations;
+                        final TwoStateOwner owner = new TwoStateOwner();
 
+                        new Handler(getMainLooper()).post(new Runnable() {
                             @Override
-                            public void handleMessage(android.os.Message msg) {
-                                Log.i(account.name + "/" + folder.name + " observe=" + msg.what);
-                                try {
-                                    if (msg.what == 0) {
-                                        liveOperations.removeObserver(observer);
-                                        handling.clear();
-                                    } else {
-                                        liveOperations = db.operation().liveOperations(folder.id);
-                                        liveOperations.observe(ServiceSynchronize.this, observer);
-                                    }
-                                } catch (Throwable ex) {
-                                    Log.e(ex);
-                                }
-                            }
-
-                            private Observer<List<EntityOperation>> observer = new Observer<List<EntityOperation>>() {
+                            public void run() {
+                                db.operation().liveOperations(folder.id).observe(owner, new Observer<List<EntityOperation>>() {
+                                    private List<Long> waiting = new ArrayList<>();
+                                    private List<Long> handling = new ArrayList<>();
                                     private final ExecutorService folderExecutor = Executors.newSingleThreadExecutor(Helper.backgroundThreadFactory);
                                     private final PowerManager.WakeLock wlFolder = pm.newWakeLock(
                                             PowerManager.PARTIAL_WAKE_LOCK, BuildConfig.APPLICATION_ID + ":folder." + folder.id);
@@ -927,12 +911,12 @@ public class ServiceSynchronize extends LifecycleService {
                                             });
                                         }
                                     }
-                            };
-                        };
+                                });
+                            }
+                        });
 
-                        // Start watching for operations
-                        handler.sendEmptyMessage(1);
-                        handlers.add(handler);
+                        owner.start();
+                        owners.add(owner);
                     }
 
                     // Keep alive alarm receiver
@@ -1014,9 +998,9 @@ public class ServiceSynchronize extends LifecycleService {
                     db.account().setAccountError(account.id, Helper.formatThrowable(ex));
                 } finally {
                     // Stop watching for operations
-                    for (Handler handler : handlers)
-                        handler.sendEmptyMessage(0);
-                    handlers.clear();
+                    for (TwoStateOwner owner : owners)
+                        owner.stop();
+                    owners.clear();
 
                     EntityLog.log(this, account.name + " closing");
                     db.account().setAccountState(account.id, "closing");

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

@@ -0,0 +1,28 @@
+package eu.faircode.email;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleOwner;
+import androidx.lifecycle.LifecycleRegistry;
+
+public class TwoStateOwner implements LifecycleOwner {
+    private LifecycleRegistry registry;
+
+    TwoStateOwner() {
+        registry = new LifecycleRegistry(this);
+    }
+
+    void start() {
+        registry.handleLifecycleEvent(Lifecycle.Event.ON_START);
+    }
+
+    void stop() {
+        registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP);
+    }
+
+    @NonNull
+    @Override
+    public Lifecycle getLifecycle() {
+        return registry;
+    }
+}