android: optimize notification removal on app exit, add app restart method

app/src/main/java/mw/gri/android/BackgroundService.java

@@ -24,27 +24,32 @@ public class BackgroundService extends Service {
     private final Runnable mUpdateSyncStatus = new Runnable() {
         @Override
         public void run() {
+            if (mStopped) {
+                return;
+            }
+            // Update sync status at notification.
             mNotificationBuilder.setContentText(getSyncStatusText());
             NotificationManager manager = getSystemService(NotificationManager.class);
             manager.notify(SYNC_STATUS_NOTIFICATION_ID, mNotificationBuilder.build());
-
+            // Send broadcast to MainActivity if app exit is needed after node stop.
             if (exitAppAfterNodeStop()) {
                 sendBroadcast(new Intent(MainActivity.FINISH_ACTIVITY_ACTION));
                 mStopped = true;
             }
-
+            // Repeat notification update if service is not stopped.
             if (!mStopped) {
-                mHandler.postDelayed(this, 300);
+                mHandler.postDelayed(this, 500);
             }
         }
     };
 
     @Override
     public void onCreate() {
+        // Prevent CPU to sleep at background.
         PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
         mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
         mWakeLock.acquire();
-
+        // Create channel to show notifications.
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             NotificationChannel notificationChannel = new NotificationChannel(
                     TAG, TAG, NotificationManager.IMPORTANCE_LOW
@@ -53,7 +58,7 @@ public class BackgroundService extends Service {
             NotificationManager manager = getSystemService(NotificationManager.class);
             manager.createNotificationChannel(notificationChannel);
         }
-
+        // Show notification with sync status.
         Intent i = getPackageManager().getLaunchIntentForPackage(this.getPackageName());
         PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, i, PendingIntent.FLAG_IMMUTABLE);
         mNotificationBuilder = new NotificationCompat.Builder(this, TAG)
@@ -62,8 +67,9 @@ public class BackgroundService extends Service {
                 .setSmallIcon(R.drawable.ic_stat_name)
                 .setContentIntent(pendingIntent);
         Notification notification = mNotificationBuilder.build();
+        // Start service at foreground state to prevent killing by system.
         startForeground(SYNC_STATUS_NOTIFICATION_ID, notification);
-
+        // Update sync status at notification.
         mHandler.post(mUpdateSyncStatus);
     }
 
@@ -92,17 +98,24 @@ public class BackgroundService extends Service {
 
     public void onStop() {
         mStopped = true;
-
+        // Stop updating the notification.
+        mHandler.removeCallbacks(mUpdateSyncStatus);
+        // Remove service from foreground state.
         stopForeground(Service.STOP_FOREGROUND_REMOVE);
-
+        // Remove notification.
+        NotificationManager notificationManager = getSystemService(NotificationManager.class);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            notificationManager.deleteNotificationChannel(TAG);
+        }
+        notificationManager.cancel(SYNC_STATUS_NOTIFICATION_ID);
+        // Release wake lock to allow CPU to sleep at background.
         if (mWakeLock.isHeld()) {
             mWakeLock.release();
             mWakeLock = null;
         }
-
-        mHandler.removeCallbacks(mUpdateSyncStatus);
     }
 
+    // Start the service.
     public static void start(Context context) {
         if (!isServiceRunning(context)) {
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
@@ -113,10 +126,12 @@ public class BackgroundService extends Service {
         }
     }
 
+    // Stop the service.
     public static void stop(Context context) {
         context.stopService(new Intent(context, BackgroundService.class));
     }
 
+    // Check if service is running.
     private static boolean isServiceRunning(Context context) {
         ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
         List<ActivityManager.RunningServiceInfo> services = activityManager.getRunningServices(Integer.MAX_VALUE);
@@ -130,7 +145,10 @@ public class BackgroundService extends Service {
         return false;
     }
 
+    // Get sync status text for notification from native code.
     private native String getSyncStatusText();
+    // Get sync title text for notification from native code.
     private native String getSyncTitle();
+    // Check if exit app is needed after node stop from native code.
     private native boolean exitAppAfterNodeStop();
 }

app/src/main/java/mw/gri/android/MainActivity.java

@@ -1,9 +1,7 @@
 package mw.gri.android;
 
-import android.content.BroadcastReceiver;
+import android.content.*;
-import android.content.Context;
+import android.content.pm.PackageManager;
-import android.content.Intent;
-import android.content.IntentFilter;
 import android.hardware.SensorManager;
 import android.os.Bundle;
 import android.os.Process;
@@ -27,6 +25,7 @@ public class MainActivity extends GameActivity {
         @Override
         public void onReceive(Context ctx, Intent i) {
             if (i.getAction().equals(FINISH_ACTIVITY_ACTION)) {
+                unregisterReceiver(this);
                 onExit();
             }
         }
@@ -86,11 +85,11 @@ public class MainActivity extends GameActivity {
 
     @Override
     protected void onDestroy() {
-        unregisterReceiver(mBroadcastReceiver);
-
         if (!mManualExit) {
+            unregisterReceiver(mBroadcastReceiver);
             onTermination();
         }
+
         // Temp fix: kill process after 3 seconds to prevent app hanging at next launch.
         new Thread(() -> {
             try {
@@ -117,5 +116,19 @@ public class MainActivity extends GameActivity {
         finish();
     }
 
+    // Called from native code to restart the app.
+    public void onAppRestart() {
+        BackgroundService.stop(this);
+
+        // Restart Activity.
+        Intent intent = getPackageManager().getLaunchIntentForPackage(getPackageName());
+        ComponentName componentName = intent.getComponent();
+        Intent mainIntent = Intent.makeRestartActivityTask(componentName);
+        startActivity(mainIntent);
+
+        // Kill old process.
+        Process.killProcess(Process.myPid());
+    }
+
     public native void onTermination();
 }