Why do I get a null.p.ex. on startForegrund?

Question

I want to make a Notification to control my music player and so I want to start a foreground service.

My Code:

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
protected void onStop(){
    super.onStop();
    System.out.println("Stop");
    Toast.makeText(this,"Stopped",Toast.LENGTH_SHORT).show();
    if(play_media.isPlaying()){
        PendingIntent pi = PendingIntent.getActivity(getApplicationContext(), 0,
                new Intent(getApplicationContext(), MainActivity.class),
                PendingIntent.FLAG_UPDATE_CURRENT);
        Notification notification = new Notification.Builder(mContext)
                .setContentTitle("Playing")
                .setContentText("playing a song")
                .setSmallIcon(R.drawable.ic_play)
                .setLargeIcon(list.get(mDrawerList.getCheckedItemPosition()).getAlbum_Art())
                .setContentIntent(pi)
                .build();

        mediaPlayerService =  new MediaPlayerService();
 322:       mediaPlayerService.startForeground(NOTIFICATION_ID,notification);
    }
}

Exception caught on startForeground:

02-12 18:06:08.935    4405-4405/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.Driiinx.musicslide, PID: 4405
java.lang.RuntimeException: Unable to stop activity {...com.Driiinx.musicslide.MainActivity}: java.lang.NullPointerException: class name is null
at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:3188)

...

Caused by: java.lang.NullPointerException: class name is null
        at android.content.ComponentName.<init>(ComponentName.java:63)
        at android.app.Service.startForeground(Service.java:643)
        at com.Driiinx.musicslide.MainActivity.onStop(MainActivity.java:322)

Thanks!

Answer 1

The solution is simple:

• start service explicitly (e.g. in the Activity)

  Intent serviceIntent = new Intent(this, TheService.class);  
  startService(serviceIntent);
  

• in the Service onCreate() you should call startForeground(...)

  Notification notification = ...;
  startForeground(101, notification);
  

The wrong code that caused your issue was the instantiation of service:

    mediaPlayerService =  new MediaPlayerService();