收到Messenger.default.Receive后，UWP MvvmLight更新UI

Question

I am using MVVMLight in an UWP application, I have two screens: on MainScreen I have a button to open a second screen, and I also have another button to send some data from MainScreen to the second screen. I am using

Messenger.Default.Send(someobject)

and similarly

Messenger.Default.Register<Some>(this, (action) => ReceiveMsg(action));

I have to click the button on the main screen and send data to other view. The problem is the data is not getting updated on the second screen, and causing an exception

The application called an interface that was marshalled for a different thread

I tried several ways to update UI, like this , this in fact I have tried all these possibilities like following

 private async void ReceiveMsg(Some action)
    {
        try
        {
            //await Task.Factory.StartNew(() => {
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //});

            //SharingData.UpdateScore(action);
            //DispatcherHelper.Initialize();

            //await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal
            //     , () =>
            //     {
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //     });

            //await Dispatcher.DispatchAsync(() =>
            //{
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //},1000, Windows.UI.Core.CoreDispatcherPriority.Normal);

            //await Window.Current.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
            //{
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //});

            //var views= Windows.ApplicationModel.Core.CoreApplication.Views.ToList()[0];
            //await views.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () => {
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //});


            var thiswindow = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;

            await thiswindow.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
             {
                 team1 = action.Team1;
                 this.RaisePropertyChanged("Team1");

             });

            //DispatcherHelper.CheckBeginInvokeOnUI(
            //() =>
            //{
            //    T1 = action.T1;
            //    RaisePropertyChanged(() => T1);
            //});
            //DispatcherHelper.Reset();
            //DispatcherHelper.Initialize();

        }
        catch (Exception ex)
        {
            //DispatcherHelper.Reset();
            //Console
        }
    }

I have tried all the above segments one by one, but nothing works and still getting the "marshalled for a different thread" error.

Please tell me what I am doing wrong? The property is getting update, like T1='Some Value' but not reflecting on UI and on RaisePropertyChanged its giving the exception.

Answer 1

I have to click the button on the main screen and send data to other view. The problem is the data is not getting updated on the second screen, and causing an exception

The application called an interface that was marshalled for a different thread.

The Send and Receive action of Messenger will be invoked in same thread. When you click the button in the MainScreen , the CoreWindow.Dispatcher is dispatcher of MainScreen . If you use this dispatcher to modify the content of second screen, it will throw exception.

To resolve it, you should invoke Send method in the main thread of second screen.

private async void Button_Click(object sender, RoutedEventArgs e)
{
    newView = CoreApplication.CreateNewView();
    int newViewId = 0;
    await newView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        var id = Environment.CurrentManagedThreadId;
        Frame frame = new Frame();
        frame.Navigate(typeof(SecondPage), null);
        Window.Current.Content = frame;

        Window.Current.Activate();

        newViewId = ApplicationView.GetForCurrentView().Id;
    });
    bool viewShown = await ApplicationViewSwitcher.TryShowAsStandaloneAsync(newViewId);
}

private async void SendBtn_Click(object sender, RoutedEventArgs e)
{
    await newView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        var id = Environment.CurrentManagedThreadId;
        Messenger.Default.Send("Test send message!!!");
    });
}