Question

所以我有两个按钮Start / Stop和start可以正常工作，因为每次单击start时它都从头开始。但是我是xamarin表单的新手，并不完全了解如何停止device.starttimer。

这是我目前拥有的，并且无法正常工作。（不用担心声音的东西）

//timer
    bool shouldRun = false;
    private void timer()
    {
        Device.StartTimer(TimeSpan.FromSeconds(3), () =>
        {
            // Do something
            label.Text = "Time is up!";
            //shows start button instead of stop button
            startButton.IsVisible = true;
            //hides stop button
            stopButton.IsVisible = false;
            return shouldRun;
        });
    }

    private void STOPButton_Clicked(object sender, EventArgs e)
    {
        //shows start button instead of stop button
        startButton.IsVisible = true;
        //hides stop button
        stopButton.IsVisible = false;
        //stops timer
        shouldRun = false;
        //stops sound
    }

    private void STARTButton_Clicked(object sender, EventArgs e)
    {
        //hides start button
        startButton.IsVisible = false;
        //shows stop button instead of start button
        stopButton.IsVisible = true;

        //starts timer from beginning

        timer();
        //starts sound from beginning
    }

Answer 1

您将取消令牌来源添加到运行计时器的视图中

私人CancellationTokenSource取消；

按如下所示调整您的StopButton代码：

private void STOPButton_Clicked(object sender, EventArgs e)
{
    startButton.IsVisible = true;
    //hides stop button
    stopButton.IsVisible = false;
    //stops timer
    if (this.cancellation != null)
        Interlocked.Exchange(ref this.cancellation, new CancellationTokenSource()).Cancel();
    shouldRun = false;
}

最后在计时器委托中，您创建取消令牌源

CancellationTokenSource cts = this.cancellation = new CancellationTokenSource();
Device.StartTimer(TimeSpan.FromSeconds(3), () =>
{
    if (this.cancellation != null)
        Interlocked.Exchange(ref this.cancellation, new CancellationTokenSource()).Cancel();
    // Do something
    label.Text = "Time is up!";
    //shows start button instead of stop button
    startButton.IsVisible = true;
    //hides stop button
    stopButton.IsVisible = false;
    return shouldRun;
});

基本上，它与布尔标记方法非常相似，SushiHangover在其评论中提到。但是，取消来源是线程安全的，因此从其他线程停止计时器时，您不会遇到令人讨厌的竞争状况。

如何在单击按钮时停止device.starttimer xamarin表单？

1 个答案: