CODEWITHSUNDEEP
xamarinxamarin.iosxamarin.forms
Cass
Cass

Reputation: 892

Pushing content page from background thread freezes app

In Xamarin Forms for iOS, I have a custom renderer for a ContentPage that displays a video control. In my Xamarin Forms app, this custom ContentPage is displayed inside a NavigationPage. I would like to have the video screen open when a specific message comes in via MQTT.

When I open the video page by clicking a link on the main screen, it opens as expected. I know I am receiving the message via MQTT and calling Navigation.PushModalAsync() because of console statements and breakpoints. However, the custom rendered page is not displayed and the UI of my app freezes each time after calling PushModalAsync.

Is there something else I need to do to trigger Navigation.PushModalAsync() based on receiving an MQTT notification in the background of my app?

ViewRoomsPage.axml.cs:

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class ViewRoomsPage : ContentPage
{
    public ViewRoomsPage()
    {
        InitializeComponent();
    }

    public string StreamUri { get; set; }
}

ViewRoomsPage.axml:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="MyForms.Pages.ViewRoomsPage">
<ContentPage.Content>
</ContentPage.Content>

VideoViewerRenderer.cs (video code removed; this should display a blank red screen. It also works when launched from a button on the main screen)

[assembly: ExportRenderer(typeof(ViewRoomsPage), typeof(ViewRoomsRenderer))]
namespace MyForms.IOS.NativeImplementations
{
    public class ViewRoomsRenderer : PageRenderer
    {
        private IJKFFMoviePlayerController _playerController;

        protected override void OnElementChanged(VisualElementChangedEventArgs e)
        {

            base.OnElementChanged(e);

            if (e.OldElement != null || Element == null)
            {
                return;
            }

            e.NewElement.BackgroundColor = Color.Red;
        }
    }
}

Method triggered from receiving an MQTT message

    public void PushViewRooms()
    {
        Device.BeginInvokeOnMainThread(async () =>
        {
            await Application.Current.MainPage.Navigation.PushModalAsync(new ViewRoomsPage());
        });
    }

In App.xaml.cs: 

public partial class App : Application
{
    public App()
    {
        SetupDependencies(); // using StructureMap
        Manager = DependencyContainer.Resolve<IMqttManager>();
        Manager.Connect();            

        InitializeComponent();

        var mainPage = new MainPage();
        MainPage = new NavigationPage(mainPage);
    }
}

Upvotes: 1

Views: 1887

Answers (1)

Cass
Cass

Reputation: 892

The problem was a deadlock caused by a Task.WaitAll() being triggered in another section of code running in the background.

Thanks all who helped sanity check that it wasn't something in the way the renderer was set up.

Upvotes: 0

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