如何在xamarin窗体中使用自定义渲染器更改编辑器底部边框线颜色

using Xamarin.Forms;

namespace YourNamespace
{
    public class CustomEntry : Entry
    {
        public static readonly BindableProperty BottomBorderColorProperty =
            BindableProperty.Create(nameof(BottomBorderColor), typeof(Color), typeof(CustomEntry), Color.Default);

        public Color BottomBorderColor
        {
            get { return (Color)GetValue(BottomBorderColorProperty); }
            set { SetValue(BottomBorderColorProperty, value); }
        }
    }
}

using Android.Content;
using Android.Graphics.Drawables;
using YourNamespace;
using YourNamespace.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(CustomEntry), typeof(CustomEntryRenderer))]
namespace YourNamespace.Droid
{
    public class CustomEntryRenderer : EntryRenderer
    {
        public CustomEntryRenderer(Context context) : base(context)
        {
        }

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

            if (Control != null && e.NewElement is CustomEntry customEntry)
            {
                // 创建一个底部边框线的Drawable对象
                var bottomBorder = new ShapeDrawable();
                bottomBorder.Paint.Color = customEntry.BottomBorderColor.ToAndroid();
                bottomBorder.Paint.StrokeWidth = 2;
                bottomBorder.Paint.SetStyle(Paint.Style.Stroke);

                // 设置底部边框线的Drawable为编辑器的背景
                Control.SetBackground(bottomBorder);
            }
        }
    }
}

using CoreGraphics;
using YourNamespace;
using YourNamespace.iOS;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(CustomEntry), typeof(CustomEntryRenderer))]
namespace YourNamespace.iOS
{
    public class CustomEntryRenderer : EntryRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
        {
            base.OnElementChanged(e);

            if (Control != null && e.NewElement is CustomEntry customEntry)
            {
                // 设置底部边框线的颜色
                Control.Layer.BorderColor = customEntry.BottomBorderColor.ToCGColor();
                Control.Layer.BorderWidth = 2;
            }
        }
    }
}

var customEntry = new CustomEntry
{
    Placeholder = "Enter text",
    BottomBorderColor = Color.Red // 设置底部边框线的颜色
};