Android 监听回来键|您确定要退出吗

@Override	public boolean onKeyDown(int keyCode, KeyEvent event) {		// TODO Auto-generated method stub		switch (keyCode) {		case KeyEvent.KEYCODE_BACK:			AlertDialog.Builder build=new AlertDialog.Builder(this);			build.setTitle("注意")					.setMessage("确定要退出吗？")					.setPositiveButton("确定", new DialogInterface.OnClickListener() {												@Override						public void onClick(DialogInterface dialog, int which) {							// TODO Auto-generated method stub							finish();													}					})					.setNegativeButton("取消", new DialogInterface.OnClickListener() {												@Override						public void onClick(DialogInterface dialog, int which) {							// TODO Auto-generated method stub													}					})					.show();			break;		default:			break;		}		return false;		//return super.onKeyDown(keyCode, event);			}