c# - 如何在 Xamarin C# Android 中实现 CountDownTimer 类？

Question

我是 Xamarin.Android 框架的新手。我正在研究倒数计时器，但无法像javaCountDownTimer 类那样实现。任何人都可以帮我将以下 java代码转换为 C# Xamarin android 代码。

    bar = (ProgressBar) findViewById(R.id.progress);
    bar.setProgress(total);
    int twoMin = 2 * 60 * 1000; // 2 minutes in milli seconds

    /** CountDownTimer starts with 2 minutes and every onTick is 1 second */
    cdt = new CountDownTimer(twoMin, 1000) { 

        public void onTick(long millisUntilFinished) {

            total = (int) ((dTotal / 120) * 100);
            bar.setProgress(total);
        }

        public void onFinish() {
             // DO something when 2 minutes is up
        }
    }.start();

Answer 1

为什么不System.Timers.Timer用于这个？

private System.Timers.Timer _timer;
private int _countSeconds;

void Main()
{
    _timer = new System.Timers.Timer();
    //Trigger event every second
    _timer.Interval = 1000;
    _timer.Elapsed += OnTimedEvent;
    //count down 5 seconds
    _countSeconds = 5;

    _timer.Enabled = true;
}

private void OnTimedEvent(object sender, System.Timers.ElapsedEventArgs e)
{
    _countSeconds--;

    //Update visual representation here
    //Remember to do it on UI thread

    if (_countSeconds == 0)
    {
        _timer.Stop();
    }
}

另一种方法是启动 async Task，它内部有一个简单的循环并使用CancellationToken.

private async Task TimerAsync(int interval, CancellationToken token)
{
    while (token.IsCancellationRequested)
    {
        // do your stuff here...

        await Task.Delay(interval, token);
    }
}

然后开始

var cts = new CancellationTokenSource();
cts.CancelAfter(5000); // 5 seconds

TimerAsync(1000, cts.Token);

只记得抓住TaskCancelledException.