ios - 在IOS上自定义渲染Frame的CardView

Question

我试图通过子类化Frame并制作一个自定义渲染器来在IOS Xamarin Forms上制作CardView。我想实现以下目标:



在研究设置阴影的API时，我已完成以下操作:

[assembly: ExportRenderer(typeof(CardView), typeof(CardViewRenderer))]
namespace TrabbleMobile.iOS.CustomRenderers
{
    public class CardViewRenderer : FrameRenderer
    {
        public override void Draw(CGRect rect)
        {
            var cardView = (CardView)this.Element;

            using (var context = UIGraphics.GetCurrentContext())
            {
                //nfloat cornerRadius = 2;
                float shadowOffsetWidth = 2;
                float shadowOffsetHeight = 4;
                var shadowColor = new CGColor(0, 0, 0, (nfloat)0.5);
                var boxColor = new CGColor(255, 255, 255);
                var shadowBlur = (float)0.5;
                var offset = new CGSize(shadowOffsetWidth, shadowOffsetHeight);

                context.SetShadow(offset, shadowBlur, shadowColor);

但是，它不会呈现应有的渲染，也完全没有阴影。

Answer 1

我已经做到了，而这样做的方式是通过在IOS上进行自定义渲染，这是自定义渲染器代码:

    public class CardViewRenderer : FrameRenderer
    {

        public override void Draw(CGRect rect)
        {
            SetupShadowLayer();
            base.Draw(rect);
        }

        void SetupShadowLayer()
        {
            Layer.CornerRadius = 2; // 5 Default
            if (Element.BackgroundColor == Xamarin.Forms.Color.Default)
            {
                Layer.BackgroundColor = UIColor.White.CGColor;
            }
            else
            {
                Layer.BackgroundColor = Element.BackgroundColor.ToCGColor();
            }

            Layer.ShadowRadius = 2; // 5 Default
            Layer.ShadowColor = UIColor.Black.CGColor;
            Layer.ShadowOpacity = 0.4f; // 0.8f Default
            Layer.ShadowOffset = new CGSize(0f, 2.5f);

            if (Element.OutlineColor == Xamarin.Forms.Color.Default)
            {
                Layer.BorderColor = UIColor.Clear.CGColor;
            }
            else
            {
                Layer.BorderColor = Element.OutlineColor.ToCGColor();
                Layer.BorderWidth = 1;
            }

            Layer.RasterizationScale = UIScreen.MainScreen.Scale;
            Layer.ShouldRasterize = true;
        }
    }