如何在Xamarin表单中创建浮动标签条目？

using Xamarin.Forms;

namespace YourNamespace
{
    public class FloatingLabelEntry : Entry
    {
        public static readonly BindableProperty FloatingLabelProperty =
            BindableProperty.Create(nameof(FloatingLabel), typeof(string), typeof(FloatingLabelEntry), string.Empty);

        public string FloatingLabel
        {
            get { return (string)GetValue(FloatingLabelProperty); }
            set { SetValue(FloatingLabelProperty, value); }
        }
    }
}

using Android.Content;
using Android.Graphics;
using Android.Text;
using Android.Widget;
using YourNamespace;
using YourNamespace.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

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

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

            if (Control != null && e.NewElement != null && e.NewElement is FloatingLabelEntry)
            {
                var entry = (FloatingLabelEntry)e.NewElement;
                Control.SetHintTextColor(ColorStateList.ValueOf(Android.Graphics.Color.Gray));
                Control.SetHint(entry.FloatingLabel);
                Control.SetTextSize(ComplexUnitType.Sp, 14);
                Control.SetPadding(0, 20, 0, 0);
            }
        }
    }
}

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

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

            if (Control != null && e.NewElement != null && e.NewElement is FloatingLabelEntry)
            {
                var entry = (FloatingLabelEntry)e.NewElement;
                Control.BorderStyle = UITextBorderStyle.None;
                Control.Layer.BorderWidth = 0;
                Control.Layer.CornerRadius = 0;
                Control.Layer.BackgroundColor = UIColor.Clear.CGColor;
                Control.LeftView = new UIView(new CGRect(0, 0, 10, 0));
                Control.LeftViewMode = UITextFieldViewMode.Always;
                Control.Font = UIFont.SystemFontOfSize(14);
                Control.Placeholder = entry.FloatingLabel;
            }
        }
    }
}

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:YourNamespace"
             x:Class="YourNamespace.MainPage">
    <StackLayout>
        <local:FloatingLabelEntry FloatingLabel="Username" />
        <local:FloatingLabelEntry FloatingLabel="Password" />
    </StackLayout>
</ContentPage>