Dispose Device.StartTimer, if current page is reinitialized from the mainpage - xamarin

Question

I want to stop Device.StartTimer when my current page is re-initialize from the App.cs page, but every time when page is re-initialize Device.Starttimer create new instance and function is calling multiple times.
from the links and references i get to know that it will not stop until return statement not execute, but in my case how to execute return statement outside the method, that i can not understand.
Below is my cs page code.
public partial class MediaScreen : ContentPage
{
public static readonly List<string> ImageExtensions = new List<string>
{ ".JPG", ".JPE", ".BMP", ".GIF", ".PNG" };
public static readonly List<string> videoExtensions = new List<string> {
".WAV", ".MID", ".MIDI", ".WMA", ".OGG", ".RMA", //etc
".AVI", ".MP4", ".DIVX", ".WMV", //etc
};
int i = 0;
DisplayInfo mainDisplayInfo = DeviceDisplay.MainDisplayInfo;
public MediaScreen()
{
InitializeComponent();
try
{
StartPlaying();
}
catch (Exception e)
{
}
}
public bool StartPlaying()
{
CrossMediaManager.Current.Stop();
if (i == App.localStorage.Playlist.PlayListItems.Count)
{
i = 0;
StartPlaying();
return false;
}
var data = App.localStorage.Playlist.PlayListItems[i].MediaLibrary;
string fileName = App.path + "\\" + Path.GetFileName(data.Url);
if (ImageExtensions.Contains(Path.GetExtension(fileName).ToUpperInvariant()))
{
// process image
imgPlayer.IsVisible = true;
imgPlayer.Source = fileName;
videoPlayer.IsVisible = false;
}
else
{
try
{
CrossMediaManager.Current.Play(fileName);
CrossMediaManager.Current.MediaItemFinished += finishVideo;
videoPlayer.IsVisible = true;
imgPlayer.IsVisible = false;
}
catch (Exception e1)
{
}
}
i++;
Device.StartTimer(TimeSpan.FromSeconds
(data.Duration), StartPlaying);
return false;
}
}
}

Answer 1

You can use a stoppable timer instead. It has 2 goals: it can be stopped, it can be rescheduled (if it didn't start yet you can reschedule it):
Schedule example:
public StoppableTimer<object> timerScheduled; //object is param type you want
public void LaunchTimer()
{
if (timerScheduled == null)
{
timerScheduled = new StoppableTimer<object>(TimeSpan.FromSeconds(2), OnTimerStart);
timerScheduled.Start(null); //whatever param
}
else
{
//relaunch
timerScheduled.Stop();
timerScheduled.Start(control);
}
}
So when you need to cancel the timer just call timerScheduled.Stop();
Your callback:
private void OnTimerStart(object p)
{
//StartPlaying - do your stuff
}
Class:
public class StoppableTimer<T> // T is the parameter you want to pass to timer
{
private readonly TimeSpan timespan;
private readonly Action<T> callback;
private CancellationTokenSource cancellation;
public StoppableTimer(TimeSpan timespan, Action<T> callback)
{
this.timespan = timespan;
this.callback = callback;
this.cancellation = new CancellationTokenSource();
}
public void Start(T param)
{
CancellationTokenSource cts = this.cancellation; // safe copy
Device.StartTimer(this.timespan,
() => {
if (cts.IsCancellationRequested) return false;
this.callback.Invoke(param);
return false; // or true for periodic behavior
});
}
public void Stop()
{
Interlocked.Exchange(ref this.cancellation, new CancellationTokenSource()).Cancel();
}
public void Dispose()
{
}
}