UITextFieldDelegate.ShouldReturn not triggered

Question

Hi, I'm having a problem with triggering the Completed event in custom control on iOS.

I'm implementing the CustomRadEntry as a custom control of type Entry.

public class CustomRadEntry : Entry 	
{ 		
	public event EventHandler OnCompleted;	
	public CustomRadEntry() 	
	{ }  	
	public void InvokeCompletedEvent() 	
	{ 			
		OnCompleted?.Invoke(this, null); 	
	} 
}

CustomRadEntryHandler.cs

public partial class CustomRadEntryHandler
{
	public static IPropertyMapper<CustomRadEntry, CustomRadEntryHandler> PropertyMapper = 			new PropertyMapper<CustomRadEntry, CustomRadEntryHandler>(EntryHandler.ViewMapper)
        {
            [nameof(CustomRadEntry.Text)] = MapText
        };

        public static CommandMapper<CustomRadEntry, CustomRadEntryHandler> CommandMapper = 	new(ViewCommandMapper)
        { };

        
	public CustomRadEntryHandler() : base(PropertyMapper, CommandMapper)        
	{    } 
}

CustomRadEntryHandler.MaciOS.cs

public partial class CustomRadEntryHandler : EntryHandler
	{
        protected override MauiCustomRadEntry CreatePlatformView()
        {
            return new MauiCustomRadEntry(VirtualView);
        }

        protected override void ConnectHandler(MauiTextField platformView)
        {
            base.ConnectHandler(platformView);
        }

        protected override void DisconnectHandler(MauiTextField platformView)
        {
            base.DisconnectHandler(platformView);
        }
    }

Beneath it, there is also an implementation for iOS named MauiCustomRadEntry which inherits from MauiTextField.

public class MauiCustomRadEntry : MauiTextField
	{
        private CustomRadEntry _customEntry;
        public MauiCustomRadEntry(IEntry entry)
        {
            _customEntry = (CustomRadEntry)entry;
            AddDoneButton();
            //TODO: Test if using _customEntry in this constructor is correct.
            CustomBorderUITextFieldDelegate textFieldDelegate = new 		CustomBorderUITextFieldDelegate(_customEntry);
            WeakDelegate = textFieldDelegate;
        }

        private void AddDoneButton()
        {
            var toolbar = new UIToolbar(new RectangleF(0.0f, 0.0f, 50.0f, 44.0f));

            var doneButton = new UIBarButtonItem(UIBarButtonSystemItem.Done, delegate
            {
                ResignFirstResponder();
                _customEntry.InvokeCompletedEvent();
            });

            toolbar.Items = new[] {
                        new UIBarButtonItem (UIBarButtonSystemItem.FlexibleSpace),
                        doneButton};
            InputAccessoryView = toolbar;
        }
    }

    public class CustomBorderUITextFieldDelegate : UITextFieldDelegate
    {
        private WeakReference element;

        internal Entry Element => this.element.IsAlive ? (Entry)this.element.Target : (Entry)null;

        public CustomBorderUITextFieldDelegate(Entry element) => this.element = new WeakReference((object)element);

        public override void EditingStarted(UITextField textField) => this.Element?.SetValueFromRenderer(VisualElement.IsFocusedPropertyKey, (object)true);

        public override bool ShouldReturn(UITextField textField)
        {
            textField.ResignFirstResponder();
            if (Element is CustomRadEntry customRadEntry)
            {
                customRadEntry.InvokeCompletedEvent();
            }
            //this.Element.InvokeCompletedEvent();
            return false;
        }

        public override void EditingEnded(UITextField textField, UITextFieldDidEndEditingReason reason) => this.Element?.SetValueFromRenderer(VisualElement.IsFocusedPropertyKey, (object)false);
    }

inside the MauiCustomRadEntry constructor, I assigned a WeakDelegate to a custom Delegate. Details of implementation is in the attached project. The Page containing and testing this control is CustomRadEntryPage.xaml.

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="dummyProj.Pages.CustomRadEntryPage"
             xmlns:controls="clr-namespace:dummyProj.CustomControls"
             Title="CustomRadEntryPage">
    <Grid>
        <controls:CustomRadEntry
            HorizontalOptions="Center"
            Text="heLLO WORLD"
            OnCompleted="CustomRadEntry_OnCompleted"
            ReturnType="Next"
            />
    </Grid>
</ContentPage>

CustomRadEntryPage.xaml.cs

public CustomRadEntryPage()
	{
		InitializeComponent();
	}

    void CustomRadEntry_OnCompleted(System.Object sender, System.EventArgs e)
    {
		Console.Write("Hit Done");
    }

If you run into the issue when an exception of delegate occurs, please add this line to CreateMauiApp() of AppDelegate.cs

UIApplication.CheckForEventAndDelegateMismatches = false;

When I hit Done, I expect it to trigger the ShouldReturn() of the delegate. In fact, it doesn't. I need it to invoke the completed event. Please have a look and can you give me a work-around to make this work?

Answer 1

Hello,

From the MAUI EntryHandler.iOS source code, we can see MAUI has implemented this ShouldReturn delegate method, you could overwrite it in the CustomRadEntryHandler class. Please refer to the following code:

public partial class CustomRadEntryHandler : EntryHandler
{
    protected override MauiCustomRadEntry CreatePlatformView()
    {
        return new MauiCustomRadEntry(VirtualView);
    }


   protected override bool OnShouldReturn(UITextField view)
    {
        CustomRadEntry customRadEntry = this.VirtualView as CustomRadEntry;
        customRadEntry.InvokeCompletedEvent();// Find the entry and invoke the completed event
        Debug.WriteLine("CustomRadEntryHandler Hit ");
      return base.OnShouldReturn(view);


    }
    protected override void ConnectHandler(MauiTextField platformView)
    {
        base.ConnectHandler(platformView);
        platformView.ShouldReturn += OnShouldReturn;
    }


   protected override void DisconnectHandler(MauiTextField platformView)
    {
        base.DisconnectHandler(platformView);
        platformView.ShouldReturn -= OnShouldReturn;
    }
}

Best Regards,

Wenyan Zhang

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