如何在Android代码中取消处理程序？

Question

如果没有完成,我创建1分钟延迟计时器来关闭服务.看起来像这样:

private Handler timeoutHandler = new Handler();

在onCreate()里面

timeoutHandler.postDelayed(new Runnable()
        {
            public void run()
            {
                Log.d(LOG_TAG, "timeoutHandler:run");

                DBLog.InsertMessage(getApplicationContext(), "Unable to get fix in 1 minute");
                finalizeService();
            }
        }, 60 * 1000);

如果我在这1分钟之前完成工作 - 我想取消这个延迟的事情但不确定如何.

Answer 1

你不能用匿名的Runnable真正做到这一点.如何将Runnable保存到命名变量？

Runnable finalizer = new Runnable()
    {
        public void run()
        {
            Log.d(LOG_TAG, "timeoutHandler:run");

            DBLog.InsertMessage(getApplicationContext(), "Unable to get fix in 1 minute");
            finalizeService();
        }
    };
timeoutHandler.postDelayed(finalizer, 60 * 1000);

...

// Cancel the runnable
timeoutHandler.removeCallbacks(finalizer);

Answer 2

如果你不想保留runnable的引用,你可以简单地调用:

timeoutHandler.removeCallbacksAndMessages(null);

官方文件说:

...如果token为null,则将删除所有回调和消息.

Answer 3

您可能希望postDelayed使用sendMessageDelayed类似的替换使用:

private Handler timeoutHandler = new Handler(){
    @Override
    public void handleMessage(Message msg)
    {
            switch (msg.what){
        case 1:
            ((Runnable)msg.obj).run();
            break;
        }
    }
};

然后发布消息:

Message m = Message.obtain();
m.what = 1;
m.obj = new Runnable(){
            public void run()
            {
                Log.d(LOG_TAG, "timeoutHandler:run");

                DBLog.InsertMessage(getApplicationContext(), "Unable to get fix in 1 minute");
                finalizeService();
            }
        };
timeoutHandler.sendMessageDelayed(m, 60 * 1000);

然后取消:

timeoutHandler.removeMessages(1);

没有跟踪必要的可运行.