뒤로가기버튼 눌렀을떄 반응

public boolean onKeyDown(int keyCode, KeyEvent event) {
  switch(keyCode){
  case KeyEvent.KEYCODE_BACK: // 뒤로가기 버튼을 눌렀을떄
   new AlertDialog.Builder(this)
   .setTitle("종료?")
   .setMessage("종료 하시겠습니까?")
   .setPositiveButton("종료",new DialogInterface.OnClickListener() {
    
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     finish();
     
     
    }
   })
   .setNegativeButton("취소",null)
   .show();
   break;
  
  }
  
  return true;
 }