Custom Frame renderer for unique corner radius values in android [Xamarin.Forms]

Question

I want to create a custom renderer for my frame control in fact of having a control which each corner radius values are unique, I have tried to create a custom renderer for frame control in many ways but I haven't found a "solid" solution for it, my custom renderer is not working, I also have tried to use Xamarin.Forms.PancackeView plugin but in my Xamarin.Forms version (4.3.0.991) it seems to have a bug or something related:

EXTRA : I want to implement shadow in the control frame, but as you should know, frame control by default has shadow, but the shadow in my frame is not working, is there a bug or how can I implement shadow to the custom frame renderer?

Android code for custom Frame renderer:

[assembly: ExportRenderer(typeof(TagFrame), typeof(TagFrameCustomRendererAndroid))]
namespace Sortex.Droid.CRImplementations
{
    public class TagFrameCustomRendererAndroid : FrameRenderer
    {
        public TagFrameCustomRendererAndroid(Context context) : base(context)
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Frame> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
            {
                GradientDrawable gradientDrawable = new GradientDrawable();

                float[] cornerRadius = { 100000, 100000, 0, 0, 0, 0, 100000, 100000 };
                gradientDrawable.SetCornerRadii(cornerRadius);

                SetBackgroundDrawable(gradientDrawable);
            }
        }
    }
}

TagFrame class in the shared project:

public class TagFrame : Frame
{
}

Answer 1

I want to create a custom renderer for my frame control in fact of having a control which each corner radius values are unique,

According to your description, you want to custom render frame, then you can set different corner radius. If yes, I do one sample that you can take a look:

Firstly, create CustomFrame inherit Frame, has BindableProperty CornerRadiusProperty.

public class CustomFrame:Frame
{
    public static new readonly BindableProperty CornerRadiusProperty = BindableProperty.Create(nameof(CustomFrame), typeof(CornerRadius), typeof(CustomFrame));

    public CustomFrame()
    {
        // MK Clearing default values (e.g. on iOS it's 5)
        base.CornerRadius = 0;
    }

    public new CornerRadius CornerRadius
    {
        get => (CornerRadius)GetValue(CornerRadiusProperty);
        set => SetValue(CornerRadiusProperty, value);
    }
}

Then going to Android platform,

using FrameRenderer = Xamarin.Forms.Platform.Android.AppCompat.FrameRenderer;


[assembly: ExportRenderer(typeof(CustomFrame), typeof(CustomFrameRenderer))]
namespace Framerender.Droid
{
  public  class CustomFrameRenderer: FrameRenderer
    {
        public CustomFrameRenderer(Context context)
            : base(context)
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Frame> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null && Control != null)
            {
                UpdateCornerRadius();
            }
        }

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            if (e.PropertyName == nameof(CustomFrame.CornerRadius) ||
                e.PropertyName == nameof(CustomFrame))
            {
                UpdateCornerRadius();
            }
        }

        private void UpdateCornerRadius()
        {
            if (Control.Background is GradientDrawable backgroundGradient)
            {
                var cornerRadius = (Element as CustomFrame)?.CornerRadius;
                if (!cornerRadius.HasValue)
                {
                    return;
                }

                var topLeftCorner = Context.ToPixels(cornerRadius.Value.TopLeft);
                var topRightCorner = Context.ToPixels(cornerRadius.Value.TopRight);
                var bottomLeftCorner = Context.ToPixels(cornerRadius.Value.BottomLeft);
                var bottomRightCorner = Context.ToPixels(cornerRadius.Value.BottomRight);

                var cornerRadii = new[]
                {
                    topLeftCorner,
                    topLeftCorner,

                    topRightCorner,
                    topRightCorner,

                    bottomRightCorner,
                    bottomRightCorner,

                    bottomLeftCorner,
                    bottomLeftCorner,
                };

                backgroundGradient.SetCornerRadii(cornerRadii);
            }
        }
    }
}

Now, you can use CustomFrame in PCL.

 <local:CustomFrame
        BackgroundColor="Red"
        CornerRadius="0,0,30,30"
        HasShadow="True"
        HeightRequest="100"
        VerticalOptions="CenterAndExpand"
        WidthRequest="100" />

Here is the sample at Github, you can also take a look:

https://github.com/CherryBu/CustomFrame

There are also one article about customframe:

https://progrunning.net/customizing-corner-radius/