xamarin.from上可以使用本身的button实现圆角带图标的按钮，但是没有半圆角的按钮实现，需要自己使用Renderer重新写过来重写一个button。
下面是一个重写的带边框的方式，代码如下：
1 using UIKit; 2 using Xamarin.Forms.Platform.iOS; 3 using Xamarin.Forms; 4 using CoreAnimation; 5 using System.ComponentModel; 6 7 [assembly: ExportRenderer(typeof(Test.Renderers.MyRadiusButton), typeof(Test.iOS.Renderers.MyRadiusButton))] 8 namespace Test.iOS.Renderers 9 { 10 public class MyRadiusButton : ButtonRenderer 11 { 12 bool btnStatus = true; 13 bool radiusLeft = true; 14 protected override void OnElementChanged(ElementChangedEventArgs<Button> e) 15 { 16 base.OnElementChanged(e); 17 Test.Renderers.MyRadiusButton view = Element as Test.Renderers.MyRadiusButton; 18 radiusLeft = view.RadiusLeft; 19 if (e.OldElement == null) 20 { 21 UIBezierPath maskPath; 22 23 24 double widthLength = 600 / 2 - 10; 25 maskPath = UIBezierPath.FromRoundedRect(new CoreGraphics.CGRect(0, 0, widthLength, 35), UIRectCorner.TopLeft | UIRectCorner.BottomLeft, new CoreGraphics.CGSize(18, 18)); 26 27 CAShapeLayer maskLayer = new CAShapeLayer(); 28 //maskLayer.Frame = new CoreGraphics.CGRect(0, 0, widthLength, 35); 29 maskLayer.Path = maskPath.CGPath; 30 maskLayer.StrokeColor = new CoreGraphics.CGColor(0, 0, 0);//边框颜色 31 32 CAShapeLayer borderLayer = new CAShapeLayer(); 33 borderLayer.Path = maskPath.CGPath; 34 borderLayer.Frame = new CoreGraphics.CGRect(0, 0, widthLength, 35); 35 borderLayer.FillColor = new CoreGraphics.CGColor(1, 1, 1, 0f); 36 borderLayer.StrokeColor = new CoreGraphics.CGColor(0.23f, 0.72f, 0.47f, 1.0f); 37 borderLayer.LineWidth = 1; 38 39 Control.Layer.Mask = maskLayer; 40 Control.Layer.AddSublayer(borderLayer); 41 Control.Layer.MasksToBounds = true; 42 Control.SetTitleColor(UIColor.FromRGB(255, 255, 255), UIControlState.Normal); 43 Control.BackgroundColor = UIColor.FromRGB(59, 183, 120); 44 45 view.Clicked += (sender, even) => 46 { 47 if (!view.BtnSelected) 48 { 49 if (btnStatus) 50 { 51 Control.SetTitleColor(UIColor.FromRGB(59, 183, 120), UIControlState.Normal); 52 Control.BackgroundColor = UIColor.FromRGB(222, 222, 222); 53 btnStatus = !btnStatus; 54 } 55 else 56 { 57 Control.SetTitleColor(UIColor.FromRGB(255, 255, 255), UIControlState.Normal); 58 Control.BackgroundColor = UIColor.FromRGB(59, 183, 120); 59 btnStatus = !btnStatus; 60 } 61 view.BtnClickAction?.Invoke(); 62 } 63 }; 64 65 } 66 } 67 } 68 }