the application stopped when stop playing the sound

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http://stackoverflow.com – I created my Android app to play sound when user select option value on i did my code well. All thing worked well but when i added my code to make user mute or stop the sound when click on lock button at his mobile it worked well but when i rotate the mobile horizontal the error " the application stopped unexpectedly " occurred. I checked my code and i reached that the error at onPause method . @Override protected void onResume() { IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(Intent.ACTION_SCREEN_OFF); registerReceiver(new IntentListener(), intentFilt (HowTos)