signalr method not being triggered in onSleep event xamarin.forms

Question

i am trying to implement a way to detect the user's status if online or offline. so i used the lifecycle events in xamarin.forms. i set online flag to false when the app goes to the background, then send it using a signalr hub method:

 async  protected override void OnSleep()
        {
                online = false;
                
                if (!string.IsNullOrEmpty(Preferences.Get("userid", "")) && !string.IsNullOrEmpty(Preferences.Get("permission", "")))
                {
                    if (Preferences.Get("permission", "") == "Student")
                    {
                        try
                        {
                             await SendMessage(Preferences.Get("userid", ""), false);
                        }
                        catch (Exception exp)
                        {
                            MessagingCenter.Send(this, App.UpdateStatusErrorMessage, exp.Message);
                        }

                    
                        await updateuserstatus(Preferences.Get("userid", ""));

                    }
                    
                }
       
        }

but it is not being triggered unless it is the second time or third time the app goes to the background. i tried adding Task.Delay(500) then calling base.OnSleep() but nothing is working. any suggestions? thanks in advance

Answer 1

Since you want to update your presence when the user navigates away from the page, the Page.OnDisappearing Method may be more suitable.

protected override async void OnDisappearing()
{
    base.OnDisappearing();
    
    online = false;
    
    if (!string.IsNullOrEmpty(Preferences.Get("userid", "")) && !string.IsNullOrEmpty(Preferences.Get("permission", "")))
    {
        if (Preferences.Get("permission", "") == "Student")
        {
            try
            {
                await SendMessage(Preferences.Get("userid", ""), false);
            }
            catch (Exception exp)
            {
                MessagingCenter.Send(this, App.UpdateStatusErrorMessage, exp.Message);
            }
            
            await updateuserstatus(Preferences.Get("userid", ""));
        }
    }
}

And if you still want use OnSleep event, you can try the code below.

protected override void OnSleep()
{
    online = false;

    if (!string.IsNullOrEmpty(Preferences.Get("userid", "")) && !string.IsNullOrEmpty(Preferences.Get("permission", "")))
    {
        if (Preferences.Get("permission", "") == "Student")
        {
            Task.Run(async () =>
            {
                try
                {
                    await SendMessage(Preferences.Get("userid", ""), false);
                }
                catch (Exception exp)
                {
                    Device.BeginInvokeOnMainThread(() =>
                    {
                        MessagingCenter.Send(this, App.UpdateStatusErrorMessage, exp.Message);
                    });
                }

                await updateuserstatus(Preferences.Get("userid", ""));
            });
        }
    }

    base.OnSleep();
}