Android 监听返回键|您确定要退出吗

@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {// TODO Auto-generated method stubswitch (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() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stubfinish();}}).setNegativeButton("取消", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stub}}).show();break;default:break;}return false;//return super.onKeyDown(keyCode, event);}