android 双击退出

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK){
if (isDouble){
//点击第二次的时候
finish();
}else{
//点击第一次的时候
isDouble = true;
Toast.makeText(this, "再次点击退出", Toast.LENGTH_SHORT).show();
//判断时间
Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
isDouble = false;
}
},2000);
}
}

return super.onKeyDown(keyCode, event);
}