Fix MediaPlaybackService exception issue.

b/194427284

Change-Id: I7b405366675c06d5c35a6817e0cba68d60783196
(cherry picked from commit 8f5cfd959c2eaba3546708c8425efa1c14bbbf56)

starboard/android/apk/app/src/main/java/dev/cobalt/coat/MediaPlaybackService.java

@@ -35,7 +35,6 @@ public class MediaPlaybackService extends Service {
   private static final int NOTIFICATION_ID = 193266736; // CL number for uniqueness.
   private static final String NOTIFICATION_CHANNEL_ID = "dev.cobalt.coat media playback service";
   private static final String NOTIFICATION_CHANNEL_NAME = "Media playback service";
-  private Context context;
 
   @Override
   public void onCreate() {
@@ -46,7 +45,6 @@ public void onCreate() {
       return;
     }
     getStarboardBridge().onServiceStart(this);
-    context = getApplicationContext();
   }
 
   @Override
@@ -70,7 +68,6 @@ public void onDestroy() {
       return;
     }
     getStarboardBridge().onServiceDestroy(this);
-    context = null;
     super.onDestroy();
     Log.i(TAG, "Destroying the Media playback service.");
   }
@@ -92,7 +89,7 @@ public void stopService() {
   private void hideNotification() {
     Log.i(TAG, "Hiding notification after stopped the service");
     NotificationManager notificationManager =
-        (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+        (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
     notificationManager.cancel(NOTIFICATION_ID);
   }
 
@@ -105,7 +102,7 @@ private void createChannel() {
   @RequiresApi(26)
   private void createChannelInternalV26() {
     NotificationManager notificationManager =
-        (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+        (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
     NotificationChannel channel =
         new NotificationChannel(
             NOTIFICATION_CHANNEL_ID,
@@ -115,7 +112,7 @@ private void createChannelInternalV26() {
     try {
       notificationManager.createNotificationChannel(channel);
     } catch (IllegalArgumentException e) {
-
+      // intentional empty.
     }
   }
 
@@ -128,13 +125,13 @@ public void deleteChannel() {
   @RequiresApi(26)
   private void deleteChannelInternalV26() {
     NotificationManager notificationManager =
-        (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+        (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
     notificationManager.deleteNotificationChannel(NOTIFICATION_CHANNEL_ID);
   }
 
   Notification buildNotification() {
     NotificationCompat.Builder builder =
-        new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
+        new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
             .setShowWhen(false)
             .setPriority(NotificationCompat.PRIORITY_MIN)
             .setSmallIcon(android.R.drawable.stat_sys_warning)

starboard/android/apk/app/src/main/java/dev/cobalt/coat/StarboardBridge.java

@@ -171,6 +171,10 @@ protected void onServiceDestroy(Service service) {
   protected void startMediaPlaybackService() {
     Service service = serviceHolder.get();
     if (service == null) {
+      if (appContext == null) {
+        Log.w(TAG, "Activiy already destoryed.");
+        return;
+      }
       Log.i(TAG, "Cold start - Instantiating a MediaPlaybackService.");
       Intent intent = new Intent(appContext, MediaPlaybackService.class);
       appContext.startService(intent);