Intermittent NullReferenceException when calling MediaPicker.Default.CapturePhotoAsync() & Email.Default.ComposeAsync

Question

A user has reported an issue on an iPhone (iOS 17.3.1) where an exception has been repeatedly thrown when the app calls MediaPicker.Default.CapturePhotoAsync() & Email.Default.ComposeAsync. After a few phone and app restarts the issue seemed to resolve itself. The exceptions are:

EX: System.NullReferenceException: The current view controller can not be detected.

at Microsoft.Maui.ApplicationModel.WindowStateManagerExtensions.GetCurrentUIViewController(IWindowStateManager , Boolean )

at Microsoft.Maui.ApplicationModel.Communication.EmailImplementation.ComposeWithMailCompose(EmailMessage )

at Microsoft.Maui.ApplicationModel.Communication.EmailImplementation.ComposeAsync(EmailMessage )

at MyApp.OnEmail(Object sender, EventArgs e)

EX: System.NullReferenceException: The current view controller can not be detected.

at Microsoft.Maui.ApplicationModel.WindowStateManagerExtensions.GetCurrentUIViewController(IWindowStateManager , Boolean )

at Microsoft.Maui.Media.MediaPickerImplementation.PhotoAsync(MediaPickerOptions , Boolean , Boolean )

at MyApp.ShowPhotoSourceSelectionAsync()

Cut down version of code:

public partial class App : Application

{

    public App()

    {

        MainPage = new LoginPage();

    }

}

public partial class LoginPage : ContentPage

{

private async void SignInButton_Clicked(object sender, EventArgs e)

{

	App.Current.MainPage = new NavigationPage(new MainPagePhone());

}

}

public partial class MainPagePhone : ContentPage

{

    protected override void OnAppearing()

	{        

		var detailPage = DataCollectorSubmissionDetailPage.CreatePage(viewModel.Title, dataCollectorSubmissionViewModel);

        await Navigation.PushModalAsync(new NavigationPage(detailPage));

						

	}

}

public partial class DataCollectorSubmissionDetailPage : ContentPage

{

    public StackLayout FormContent

    {

        get; private set;

    }

	

	public static DataCollectorSubmissionDetailPage CreatePage(string title, DataCollectorSubmissionViewModel viewModel)

    {

		var sectionControl = new DataCollectorSectionControl();

		FormContent.Children.Add(sectionControl);

		mainScrollView.Content = FormContent; // This is a scroll view in the xaml

    }

}

public class DataCollectorSectionControl : VerticalStackLayout

{

public StackLayout FieldControls { get; private set; }



public DataCollectorSectionControl()

{

BaseFieldControl control = field.CreateControl(_viewModel, _readOnly, _openToolTipPDF);

FieldControls.Children.Add(control);

Children.Add(FieldControls);

}

}

public class PhotoFieldControl : BaseFieldControl

{

public PhotoFieldControl(PhotoField photoField, DataCollectorSubmissionViewModel viewModel, bool readOnly, Action<string, string> openToolTipPDFAction) : base(photoField, viewModel, readOnly, openToolTipPDFAction)

{

    var grid = new Grid();

    grid.Add(CreateFieldLabel(_photoField.FieldName, _photoField.IsMandatory), 0, 0);

    grid.Add(CreateValueView(FieldValueLabel), 0, 1);

    grid.Add(image, 1, 0);

    grid.SetRowSpan(image, 2);

    var children = new View[] { grid };

    ConstructField(children, CreateFieldTapGestureRecogniser(ReadOnly), photoField);

}



public override BaseFieldControl CreateControl(DataCollectorSubmissionViewModel viewModel, bool readOnly, Action<string, string> openToolTipPDFAction)

{            

return new PhotoFieldControl(this, viewModel, readOnly, openToolTipPDFAction);

}

	

public async Task OnTapped()

{

	FileResult file = await MediaPicker.Default.CapturePhotoAsync();

}		



public class BaseFieldControl : StackLayout

{



    protected virtual void ConstructField(IList<View> children, IList<TapGestureRecognizer> gestureRecognizers, Field field)

    {

        StackLayout stackLayout = new StackLayout();

        foreach (View child in children)

        {

            stackLayout.Children.Add(child);

        }

        if (gestureRecognizers != null)

        {

            foreach (TapGestureRecognizer gestureRecognizer in gestureRecognizers)

            {

                stackLayout.GestureRecognizers.Add(gestureRecognizer);

            }

        }

        ConstructField(stackLayout, field);

    }

	protected virtual void ConstructField(StackLayout containerLayout, Field field)

    {

        AddStackLayoutStyleBinding(containerLayout);

        containerLayout.BindingContext = field;

        Children.Add(containerLayout);

    }		

}