How to schedule a repeating task to count down a number in windows phone 8

Question

I need to just have a simple task that runs as long as the user is on one specific screen. On this screen there is a count down timer.

I looked into Background Agents - but that seems not to be the right approach.

Basically it should work like this: The user goes to this one screen, presses start and the cont down timer starts to count down - every 30 seconds update is perfectly ok.

How should I do this on WP8 ?

Answer 1

You should use a DispatcherTimer as wkempf points out. Pretty simple to create actually. Something like this (where you have a TextBlock named countText in your xaml:

public partial class MainPage : PhoneApplicationPage
{
    private DispatcherTimer _timer;
    private int _countdown;

    // Constructor
    public MainPage()
    {
        InitializeComponent();

        _countdown = 100;
        _timer = new DispatcherTimer();
        _timer.Interval = TimeSpan.FromSeconds(1);
        _timer.Tick += (s, e) => Tick();
        _timer.Start();
    }

    private void Tick()
    {
        _countdown--;

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

        countText.Text = _countdown.ToString();
    }
}