menue funktioniert nicht mehr

@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {if ((keyCode == KeyEvent.KEYCODE_BACK)) {
	  AlertDialog.Builder   beendenDialog  = new AlertDialog.Builder(this);	  	  beendenDialog.setMessage("Programm beenden?");
	  beendenDialog.setPositiveButton("JA", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {           finish();                  }
      });	  beendenDialog.setNegativeButton("NEIN", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {          // do nix          }
      });	  AlertDialog dialog = beendenDialog.create();	  beendenDialog.show();}return true;}