How to increase number label when holding down mouse button?

Question

C# Calling a function repeatedly to increase value of label automatically

This is a WPF program. It has a label on it (minuteTimerLabel) that displays a two digit number, starting from 00, 01, 02 and so on up to 99. I want two features from this label. First, when the left mouse button goes up on the label (simulating a click), the number increases by 1. I have been able to implement this. But I have problem with the second feature.

    private void MinuteTimerLabel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        while(true)
        {
            if (timerMinute == 99)
            {
                return;
            }
            timerMinute += 1;
            minuteTimerLabel.Content = String.Format("{0:00}", timerMinute);
            Thread.Sleep(250);
        }
    }

When the left mouse button is held down on the label for a few seconds, the number should keep increasing one by one automatically. timerMinute is a global int variable. With my current code, the entire program locks up and nothing works. When I remove the while(true), number increases only once when pressing mouse down. If I release the mouse and press again, it works but again only once.

Answer 1

To avoid locking up the UI you need to use some form of async coding. I'd suggest using Microsoft's Reactive Framework.

NuGet "System.Reactive.Windows.Threading" to get the bits and add using System.Reactive.Linq; to the top of your code.

Then you can do this:

    private IDisposable _subscription = null;

    private void MinuteTimerLabel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _subscription =
            Observable
                .Interval(TimeSpan.FromMilliseconds(250.0))
                .Select(x => String.Format("{0:00}", x))
                .ObserveOnDispatcher()
                .Subscribe(x => MinuteTimerLabel.Content = x);
    }

    private void MinuteTimerLabel_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        _subscription.Dispose();
    }

It's super simple and super clean.

---

private IDisposable _subscription = null;

private int _counter = 0;

private void MinuteTimerLabel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    _subscription =
        Observable
            .Interval(TimeSpan.FromMilliseconds(250.0))
            .Select(x => String.Format("{0:00}", x))
            .ObserveOnDispatcher()
            .Subscribe(x => MinuteTimerLabel.Content = _counter++ % 100);
}

private void MinuteTimerLabel_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    _subscription.Dispose();
}

Answer 2

You need to bind couple of event in this case, PreviewMouseDown and PreviewMouseUp . Then calculate time different between it and increament the value for lable on ticks/secs.

Like this

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        PreviewMouseDown += Window3_PreviewMouseDown;
        PreviewMouseUp += Window3_PreviewMouseUp;
    }

    DateTime mouseDown;
    private void Window3_PreviewMouseDown(object sender, MouseButtonEventArgs e)
    {
        mouseDown = DateTime.Now;
    }

    private void Window3_PreviewMouseUp(object sender, MouseButtonEventArgs e)
    {
        var seconds = DateTime.Now.Subtract( mouseDown ).Seconds;

        //Condition code goes here..
        minuteTimerLabel.Content = seconds;
    }
}

Answer 3

Try the below code:

The code will run in the another thread un-blocking the Main Thread .

private void MinuteTimerLabel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    new Thread(Timer).Start();
}

private void Timer() {
    while(true)
    {
        if (timerMinute == 99)
        {
            return;
        }
        timerMinute += 1;
        minuteTimerLabel.Content = String.Format("{0:00}", timerMinute);
        Thread.Sleep(250);
    }
}

Answer 4

Good fit for a CancellationToken and Async Await Pattern

private CancellationTokenSource _cs;
private int _timerMinute =0;

private async void Label1_OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
   _cs?.Cancel();
   _cs?.Dispose();
   _cs = new CancellationTokenSource();
   try
   {
      while (!_cs.Token.IsCancellationRequested)
      {
         await Task.Delay(200, _cs.Token);

         Label1.Content = $"{++_timerMinute:00}";
      }
   }
   catch (OperationCanceledException) {}
}

private void Label1_OnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
   _cs?.Cancel();
   _cs?.Dispose();
}

Also if you wanted to be tricky you could add weight to it the more the mouse is down, by altering the delay