create custom view handler just for android and ios

Question

I use maui only want to for android and ios. and create an custom view MyEntry and viewHandler MyEntryViewHandler 1.MyEntryViewHandler.iOS 2.MyEntryViewHandler.android.cs and create MapText

public static void MapText(MyEntryViewHandler handler,MyEntry view)
{
}

but it tells that there is no MapText unless I create MyEntryViewHandler.window.cs in MyEntryViewHandler.cs public static PropertyMapper<Controls.MyEntry, MyEntryViewHandler> Mapper=new (ViewMapper) { [nameof(Controls.PoEntry.Text)] = MapText } MyEntryViewHandler cannot use for PropertyMapper<TVirtualView,TViewHandler> 's parameter TViewHandler why?

Answer 1

Hello,

You need to add PropertyMapper in the EntryViewHandler, then you can mapper your properties of CustomEntry and Native platform controls. But you do not need to create MyEntryViewHandler.window.cs just for android and ios. If you Configure filename-based multi-targeting

Here are completely steps to create a EntryViewHandler.

Firstly, based on your description, you create a custom View with tested properties like following code.

public class CustomEntry : View, ICustomEntry
{
    public string Text { get; set; }
    public Color TextColor { get; set; }
}
public interface ICustomEntry : IView
{
    public string Text { get; }
    public Color TextColor { get; }
}

Then, you can create a Handlers folder in your MAUI project, Add MyEntryHandler.cs, MyEntryHandler.android.cs and MyEntryHandler.ios.cs in this Handlers folder.

MyEntryHandler.cs file is an empty partial class like following code.

namespace MauiPopAsyncDemo.Handlers
{
    public partial class MyEntryHandler
    {

    }

}

MyEntryHandler.android.cs file, you need to add PropertyMapper, then you can create a relationship between native android control(AppCompatEditText) and your customEntry. By the way, please do not forget to add CustomEntryMapper to your MyEntryHandler's constrcutor's base method like following code.

#if  ANDROID
using AndroidX.AppCompat.Widget;
using Android.Content;
#endif

using Microsoft.Maui.Handlers;
using Microsoft.Maui.Controls.Compatibility.Platform.Android;

namespace MauiPopAsyncDemo.Handlers
{
    public partial class MyEntryHandler :ViewHandler<ICustomEntry, AppCompatEditText>
    {
        public MyEntryHandler() : base(CustomEntryMapper)
        {

       }
       public static PropertyMapper<ICustomEntry, MyEntryHandler> CustomEntryMapper = new PropertyMapper<ICustomEntry, MyEntryHandler>(ViewHandler.ViewMapper)
        {
            [nameof(ICustomEntry.Text)] = MapText,
            [nameof(ICustomEntry.TextColor)] = MapTextColor,
        };
       protected override AppCompatEditText CreatePlatformView()
        {
            return new AppCompatEditText(Context);
        }
       static void MapText(MyEntryHandler handler, ICustomEntry entry)
        {
            handler.PlatformView.Text= entry.Text;
        }
       static void MapTextColor(MyEntryHandler handler, ICustomEntry entry)
        {
            handler.PlatformView?.SetTextColor(entry.TextColor.ToAndroid())  ;
        }
   }
}

MyEntryHandler.ios.cs I donot know which control that you want to custom, SO I add an empty partial class for testing.

namespace MauiPopAsyncDemo.Handlers
{
    public partial class MyEntryHandler
    {


   }
}

In the end, you need to register this handler. I do not implement iOS platform. So I just register for android platform. I test above code; it could run in android platform.

 public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            })
            .ConfigureMauiHandlers(handlers =>
            {
#if __ANDROID__
                 handlers.AddHandler(typeof(CustomEntry), typeof(MauiPopAsyncDemo.Handlers.MyEntryHandler));
#endif
            }); ;


#if DEBUG
        builder.Logging.AddDebug();
#endif

       return builder.Build();
    }

Best Regards, Leon Lu

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