@Override public void registerListener(RadioListener mRadioListener){
  if (isServiceConnected)   mService.registerListener(mRadioListener);
 else   mRadioListenerQueue.add(mRadioListener);
}

@ Override public void registerListener ( RadioListener mRadioListener ) { if ( isServiceConnected ) mService . registerListener ( mRadioListener ) ; else mRadioListenerQueue . add ( mRadioListener ) ; }
register listener to listen radio service actions
