Xamarin Forms Visual Studioのレイアウトにグラデーション背景を追加する

Question

私はXamarin Formsの初心者で、MenuのContentPageを作成します。背景に線形グラデーション色が必要です。しかし、背景のグラデーションカラーを作成する方法を教えてくれるリンクは見つかりません。また、Androidのセレクターのようなボタンの背景にその色の場所が必要です。何か情報があれば返信してください。

Answer 1

以下のコードでは、StackLayoutのレイアウトを置き換えるだけで別のレイアウトを書きたい場合は、StackLayoutで作成する下の任意のレイアウトに水平および垂直グラデーション（#regionに配置）を設定できます。

PCL：で

using System;
using Xamarin.Forms;

namespace GradientColor
 {
   public class GradientColorStack : StackLayout
    {
      public Color StartColor { get; set; }
      public Color EndColor { get; set; }
    }
 }

Xamarin.Android:

  using System;
  using GradientColor;
  using GradientColor.Droid;
  using Xamarin.Forms;
  using Xamarin.Forms.Platform.Android;
  [Assembly: ExportRenderer(typeof(GradientColorStack), typeof(GradientColorStackRenderer))]

 namespace GradientColor.Droid
  {
     public class GradientColorStackRenderer : VisualElementRenderer<StackLayout>
       {
    private Color StartColor { get; set; }
    private Color EndColor { get; set; }

    protected override void DispatchDraw(global::Android.Graphics.Canvas canvas)
      {
        #region for Vertical Gradient
        //var gradient = new Android.Graphics.LinearGradient(0, 0, 0, Height,
        #endregion

        #region for Horizontal Gradient
     var gradient = new Android.Graphics.LinearGradient(0, 0, Width, 0,
          #endregion

            this.StartColor.ToAndroid(),
            this.EndColor.ToAndroid(),
            Android.Graphics.Shader.TileMode.Mirror);

        var Paint = new Android.Graphics.Paint()
        {
            Dither = true,
        };
        Paint.SetShader(gradient);
        canvas.DrawPaint(Paint);
        base.DispatchDraw(canvas);
    }

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

        if (e.OldElement != null || Element == null)
        {
            return;
        }
        try
        {
            var stack = e.NewElement as GradientColorStack;
            this.StartColor = stack.StartColor;
            this.EndColor = stack.EndColor;
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine(@"ERROR:", ex.Message);
        }
      }
   }
}

Xamarin.iOS：

  using System;
  using CoreAnimation;
  using CoreGraphics;
  using GradientColor;
  using GradientColor.iOS;
  using Xamarin.Forms;
  using Xamarin.Forms.Platform.iOS;
  [Assembly: ExportRenderer(typeof(GradientColorStack), typeof(GradientColorStackRenderer))]

 namespace GradientColor.iOS
   {
public class GradientColorStackRenderer : VisualElementRenderer<StackLayout>
    {
      public override void Draw(CGRect rect)
      {
        base.Draw(rect);
        GradientColorStack stack = (GradientColorStack)this.Element;
        CGColor startColor = stack.StartColor.ToCGColor();

        CGColor endColor = stack.EndColor.ToCGColor();

        #region for Vertical Gradient

        var gradientLayer = new CAGradientLayer();

        #endregion

        #region for Horizontal Gradient

        //var gradientLayer = new CAGradientLayer()
        //{
        //  StartPoint = new CGPoint(0, 0.5),
        //  EndPoint = new CGPoint(1, 0.5)
        //};

        #endregion



        gradientLayer.Frame = rect;
        gradientLayer.Colors = new CGColor[] { startColor, endColor 
        };

        NativeView.Layer.InsertSublayer(gradientLayer, 0);
      }
    }
 }

XAMLの場合

 <?xml version="1.0" encoding="utf-8"?>
 <ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.Microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:GradientColor; Assembly:GradientColor" x:Class="GradientColor.GradientColorPage">
 <Grid VerticalOptions="FillAndExpand" RowSpacing="0">
    <Grid.RowDefinitions>
        <RowDefinition Height="*"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Grid Grid.Row="0" BackgroundColor="Olive">
         <StackLayout VerticalOptions="Center">
            <Label Text="Normal color for stacklayout" HorizontalTextAlignment="Center" VerticalTextAlignment="Center"  TextColor="White"/>
         </StackLayout>
    </Grid>
    <Grid Grid.Row="1">
         <local:GradientColorStack StartColor="Green" EndColor="Red">
               <StackLayout VerticalOptions="CenterAndExpand">
               <Label Text="Gradient color for StackLayout" HorizontalTextAlignment="Center" VerticalTextAlignment="Center"   TextColor="White"/>
               </StackLayout>

         </local:GradientColorStack>
     </Grid>
   </Grid>
  </ContentPage>

Answer 2

Xamarin.Formsアプリでフル機能のグラデーションが必要な人のために、私のコードがあります：

PCLで

GradientLayout.cs

using Xamarin.Forms;

namespace MyProject.Renderers
{
    public class GradientLayout : StackLayout
    {
        public string ColorsList { get; set; }

        public Color[] Colors
        {
            get
            {
                string[] hex = ColorsList.Split(',');
                Color[] colors = new Color[hex.Length];

                for (int i = 0; i < hex.Length; i++)
                {
                    colors[i] = Color.FromHex(hex[i].Trim());
                }

                return colors;
            }
        }

        public GradientColorStackMode Mode { get; set; }
    }
}

GradientColorStackMode.cs

namespace MyProject.Renderers
{
    public enum GradientColorStackMode
    {
        ToRight,
        ToLeft,
        ToTop,
        ToBottom,
        ToTopLeft,
        ToTopRight,
        ToBottomLeft,
        ToBottomRight
    }
}

iOSプロジェクト内

GradientLayoutRenderer.cs

using CoreAnimation;
using CoreGraphics;
using MyProject.Renderers;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[Assembly: ExportRenderer(typeof(GradientLayout), typeof(GradientLayoutRenderer))]

namespace MyProject.iOS.Renderers
{
    public class GradientLayoutRenderer : VisualElementRenderer<StackLayout>
    {
        public override void Draw(CGRect rect)
        {
            base.Draw(rect);
            GradientLayout layout = (GradientLayout)Element;

            CGColor[] colors = new CGColor[layout.Colors.Length];

            for (int i = 0, l = colors.Length; i < l; i++)
            {
                colors[i] = layout.Colors[i].ToCGColor();
            }

            var gradientLayer = new CAGradientLayer();

            switch (layout.Mode)
            {
                default:
                case GradientColorStackMode.ToRight:
                    gradientLayer.StartPoint = new CGPoint(0, 0.5);
                    gradientLayer.EndPoint = new CGPoint(1, 0.5);
                    break;
                case GradientColorStackMode.ToLeft:
                    gradientLayer.StartPoint = new CGPoint(1, 0.5);
                    gradientLayer.EndPoint = new CGPoint(0, 0.5);
                    break;
                case GradientColorStackMode.ToTop:
                    gradientLayer.StartPoint = new CGPoint(0.5, 0);
                    gradientLayer.EndPoint = new CGPoint(0.5, 1);
                    break;
                case GradientColorStackMode.ToBottom:
                    gradientLayer.StartPoint = new CGPoint(0.5, 1);
                    gradientLayer.EndPoint = new CGPoint(0.5, 0);
                    break;
                case GradientColorStackMode.ToTopLeft:
                    gradientLayer.StartPoint = new CGPoint(1, 0);
                    gradientLayer.EndPoint = new CGPoint(0, 1);
                    break;
                case GradientColorStackMode.ToTopRight:
                    gradientLayer.StartPoint = new CGPoint(0, 1);
                    gradientLayer.EndPoint = new CGPoint(1, 0);
                    break;
                case GradientColorStackMode.ToBottomLeft:
                    gradientLayer.StartPoint = new CGPoint(1, 1);
                    gradientLayer.EndPoint = new CGPoint(0, 0);
                    break;
                case GradientColorStackMode.ToBottomRight:
                    gradientLayer.StartPoint = new CGPoint(0, 0);
                    gradientLayer.EndPoint = new CGPoint(1, 1);
                    break;
            }

            gradientLayer.Frame = rect;
            gradientLayer.Colors = colors;

            NativeView.Layer.InsertSublayer(gradientLayer, 0);
        }
    }
}

Android Project

GradientLayoutRenderer.cs

using System;
using Android.Content;
using MyProject.Renderers;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[Assembly: ExportRenderer(typeof(GradientLayout), typeof(GradientLayoutRenderer))]

namespace MyProject.Droid.Renderers
{
    public class GradientLayoutRenderer : VisualElementRenderer<StackLayout>
    {
        private Color[] Colors { get; set; }

        private GradientColorStackMode Mode { get; set; }

        public GradientLayoutRenderer(Context ctx) : base(ctx)
        { }

        protected override void DispatchDraw(global::Android.Graphics.Canvas canvas)
        {
            Android.Graphics.LinearGradient gradient;

            int[] colors = new int[Colors.Length];

            for (int i = 0, l = Colors.Length; i < l; i++)
            {
                colors[i] = Colors[i].ToAndroid().ToArgb();
            }

            switch (Mode)
            {
                default:
                case GradientColorStackMode.ToRight:
                    gradient = new Android.Graphics.LinearGradient(0, 0, Width, 0, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToLeft:
                    gradient = new Android.Graphics.LinearGradient(Width, 0, 0, 0, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToTop:
                    gradient = new Android.Graphics.LinearGradient(0, Height, 0, 0, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToBottom:
                   gradient = new Android.Graphics.LinearGradient(0, 0, 0, Height, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToTopLeft:
                    gradient = new Android.Graphics.LinearGradient(Width, Height, 0, 0, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToTopRight:
                    gradient = new Android.Graphics.LinearGradient(0, Height, Width, 0, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToBottomLeft:
                    gradient = new Android.Graphics.LinearGradient(Width, 0, 0, Height, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
                case GradientColorStackMode.ToBottomRight:
                    gradient = new Android.Graphics.LinearGradient(0, 0, Width, Height, colors, null, Android.Graphics.Shader.TileMode.Mirror);
                    break;
            }

            var Paint = new Android.Graphics.Paint()
            {
                Dither = true,
            };

            Paint.SetShader(gradient);
            canvas.DrawPaint(Paint);

            base.DispatchDraw(canvas);
        }

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

            if (e.OldElement != null || Element == null)
                return;

            try
            {
                if (e.NewElement is GradientLayout layout)
                {
                    Colors = layout.Colors;
                    Mode = layout.Mode;
                }
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(@"ERROR:", ex.Message);
            }
        }
    }
}

WPプロジェクト

GradientLayoutRenderer.cs

using System;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using MyProject.Renderers;
using Xamarin.Forms;
using Xamarin.Forms.Platform.UWP;
using Point = Windows.Foundation.Point;

[Assembly: ExportRenderer(typeof(GradientLayout), typeof(GradientLayoutRenderer))]

namespace MyProject.UWP.Renderers
{
    public class GradientLayoutRenderer : VisualElementRenderer<StackLayout, Panel>
    {
        private Color[] Colors { get; set; }

        private GradientColorStackMode Mode { get; set; }

        protected override void UpdateBackgroundColor()
        {
            base.UpdateBackgroundColor();

            LinearGradientBrush gradient;

            GradientStopCollection stopCollection = new GradientStopCollection();

            for (int i = 0, l = Colors.Length; i < l; i++)
            {
                stopCollection.Add(new GradientStop
                {
                    Color = Windows.UI.Color.FromArgb((byte)(Colors[i].A * byte.MaxValue), (byte)(Colors[i].R * byte.MaxValue), (byte)(Colors[i].G * byte.MaxValue), (byte)(Colors[i].B * byte.MaxValue)),
                    Offset = (double)i / Colors.Length
                });
            }

            switch (Mode)
            {
                default:
                case GradientColorStackMode.ToRight:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(0, 0.5),
                        EndPoint = new Point(1, 0.5)
                    };
                    break;
                case GradientColorStackMode.ToLeft:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(1, 0.5),
                        EndPoint = new Point(0, 0.5)
                    };
                    break;
                case GradientColorStackMode.ToTop:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(0.5, 1),
                        EndPoint = new Point(0.5, 0)
                    };
                    break;
                case GradientColorStackMode.ToBottom:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(0.5, 0),
                        EndPoint = new Point(0.5, 1)
                    };
                    break;
                case GradientColorStackMode.ToTopLeft:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(1, 1),
                        EndPoint = new Point(0, 0)
                    };
                    break;
                case GradientColorStackMode.ToTopRight:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(0, 1),
                        EndPoint = new Point(1, 0)
                    };
                    break;
                case GradientColorStackMode.ToBottomLeft:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(1, 0),
                        EndPoint = new Point(0, 1)
                    };
                    break;
                case GradientColorStackMode.ToBottomRight:
                    gradient = new LinearGradientBrush
                    {
                        GradientStops = stopCollection,
                        StartPoint = new Point(0, 0),
                        EndPoint = new Point(1, 1)
                    };
                    break;
            }

            Background = gradient;
        }

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

            if (e.OldElement != null || Element == null)
                return;

            try
            {
                if (e.NewElement is GradientLayout stack)
                {
                    Colors = stack.Colors;
                    Mode = stack.Mode;

                    UpdateBackgroundColor();
                }
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(@"ERROR:", ex.Message);
            }
        }
    }
}

XAMLページ内

<renderers:GradientLayout
    ColorsList="#dd8f68,#a9a9a9,#3a3939"
    Mode="ToBottomRight">

    <!-- Your content -->

</renderers:GradientLayout>

これが役立つことを願っています！

Answer 3

このクラスを使用して、SkiaSharp Nugetをプロジェクトに追加します。グラデーションが必要な場合は、xamlで使用してください。

public partial class GradientView : ContentView
{
    public Color StartColor { get; set; } = Color.Transparent;
    public Color EndColor { get; set; } = Color.Transparent;
    public bool Horizontal { get; set; } = false;

    public GradientView()
    {
        InitializeComponent();

        SKCanvasView canvasView = new SKCanvasView();
        canvasView.PaintSurface += OnCanvasViewPaintSurface;
        Content = canvasView;
    }

    void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
    {
        SKImageInfo info = args.Info;
        SKSurface surface = args.Surface;
        SKCanvas canvas = surface.Canvas;

        canvas.Clear();

        var colors = new SKColor[] { StartColor.ToSKColor(), EndColor.ToSKColor()};
        SKPoint startPoint = new SKPoint(0,0);
        SKPoint endPoint = Horizontal ? new SKPoint(info.Width, 0) : new SKPoint(0, info.Height);

        var shader = SKShader.CreateLinearGradient(startPoint, endPoint, colors, null, SKShaderTileMode.Clamp);

        SKPaint Paint = new SKPaint
        {
            Style = SKPaintStyle.Fill,
            Shader = shader
        };

        canvas.DrawRect(new SKRect(0, 0, info.Width, info.Height), Paint);
    }

Answer 4

今のところ、それを行うための実際の描画機能はありません。背景として画像を設定したい場合は、さまざまなフォルダ（hdpi、mdpi、xhdpiなど）に多くの画像を提供できます。または、 カスタムレンダラー を使用してContentPageクラスを自分の。

この議論はXamarinフォーラムで見ることができます。 https://forums.xamarin.com/discussion/22440/gradient-as-background-color

Answer 5

XFGloss プロジェクトは、XAMLを介してグラデーションを追加する機能を追加します。

例えば：

    <xfg:ContentPageGloss.BackgroundGradient>
        <xfg:Gradient Rotation="150">
            <xfg:GradientStep StepColor="White" StepPercentage="0" />
            <xfg:GradientStep StepColor="White" StepPercentage=".5" />
            <xfg:GradientStep StepColor="#ccd9ff" StepPercentage="1" />
        </xfg:Gradient>
    </xfg:ContentPageGloss.BackgroundGradient>
    ...
</ContentPage>

Answer 6

SOの最初のコメント。

na2xl answerを効果として使用する

エフェクトは異なるコンポーネントにアタッチでき、完全に再利用可能で、Formsコンポーネントをサブクラス化することを強制しません。

グラデーションの各色の開始位置と終了位置を調整するロケーションシステムを追加しました-0絶対開始/ 1絶対終了。

NetStandard lib

using System.Linq;
using Xamarin.Forms;

namespace YourProject.Effects
{
    public class GradientEffect : RoutingEffect
    {
        public GradientEffect() : base("YourCompany.GradientEffect")
        {
        }

        public string Colors { get; set; }

        public GradientMode Mode { get; set; }

        public Color[] ColorList => Colors.Split(',').Select(i => Color.FromHex(i.Trim())).ToArray();

        public string Locations { get; set; }

        public float[] LocationList => Locations.Split(',').Select(float.Parse).ToArray();

    }

    public enum GradientMode
    {
        ToRight,
        ToLeft,
        ToTop,
        ToBottom,
        ToTopLeft,
        ToTopRight,
        ToBottomLeft,
        ToBottomRight,
        Null
    }
}

iOSプロジェクト

using System;
using System.Linq;
using CoreAnimation;
using CoreGraphics;
using Foundation;
using YourProject.Effects;
using YourProject.iOS.Effects;
using Serilog;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;


[Assembly:ResolutionGroupName ("YourCompany")]
[Assembly: ExportEffect(typeof(IosGradientEffect), "GradientEffect")]
namespace YourProject.iOS.Effects
{
    public class IosGradientEffect : PlatformEffect
    {
        protected override void OnAttached()
        {
            try
            {
                var nativeView = Control ?? Container;
                var effect = (GradientEffect) Element.Effects.FirstOrDefault(e => e is GradientEffect);
                if (effect == null) return;

                var colors = effect.ColorList.Select(i => i.ToCGColor()).ToArray();

                var gradientLayer = new CAGradientLayer
                {
                    Locations = effect.LocationList?.Select(i => new NSNumber(i)).ToArray()
                };

                switch (effect.Mode)
                {
                    default:
                        gradientLayer.StartPoint = new CGPoint(0, 0.5);
                        gradientLayer.EndPoint = new CGPoint(1, 0.5);
                        break;
                    case GradientMode.ToLeft:
                        gradientLayer.StartPoint = new CGPoint(1, 0.5);
                        gradientLayer.EndPoint = new CGPoint(0, 0.5);
                        break;
                    case GradientMode.ToTop:
                        gradientLayer.StartPoint = new CGPoint(0.5, 1);
                        gradientLayer.EndPoint = new CGPoint(0.5, 0);
                        break;
                    case GradientMode.ToBottom:
                        gradientLayer.StartPoint = new CGPoint(0.5, 0);
                        gradientLayer.EndPoint = new CGPoint(0.5, 1);
                        break;
                    case GradientMode.ToTopLeft:
                        gradientLayer.StartPoint = new CGPoint(1, 1);
                        gradientLayer.EndPoint = new CGPoint(0, 0);
                        break;
                    case GradientMode.ToTopRight:
                        gradientLayer.StartPoint = new CGPoint(0, 1);
                        gradientLayer.EndPoint = new CGPoint(1, 0);
                        break;
                    case GradientMode.ToBottomLeft:
                        gradientLayer.StartPoint = new CGPoint(1, 0);
                        gradientLayer.EndPoint = new CGPoint(0, 1);
                        break;
                    case GradientMode.ToBottomRight:
                        gradientLayer.StartPoint = new CGPoint(0, 0);
                        gradientLayer.EndPoint = new CGPoint(1, 1);
                        break;
                }

                gradientLayer.Frame = nativeView.Bounds;
                gradientLayer.Colors = colors;

                nativeView.Layer.InsertSublayer(gradientLayer, 0);
            }
            catch (Exception ex)
            {
                Log.Fatal(ex.Message);
            }
        }

        protected override void OnDetached()
        {
            Log.Debug("Gradient Effect Detached");
        }
    }
}

** Androidプロジェクト**

using System;
using System.Linq;
using Android.Graphics;
using Android.Graphics.Drawables;
using Android.Graphics.Drawables.Shapes;
using YourProject.Droid.Effects;
using YourProject.Effects;
using Serilog;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[Assembly:ResolutionGroupName ("YourCompany")]
[Assembly: ExportEffect(typeof(AndroidGradientEffect), "GradientEffect")]
namespace YourProject.Droid.Effects
{
    public class AndroidGradientEffect : PlatformEffect
    {
        protected override void OnAttached()
        {
            try
            {
                var effect = (GradientEffect) Element.Effects.FirstOrDefault(e => e is GradientEffect);

                var nativeView = Control ?? Container;

                var colors = effect.ColorList.Select(i => i.ToAndroid().ToArgb()).ToArray();

                var Paint = new PaintDrawable();
                Paint.Shape = new RectShape();
                Paint.SetShaderFactory(new GradientShaderFactory(colors, effect.LocationList, Shader.TileMode.Mirror, effect.Mode));

                nativeView.SetBackgroundDrawable(Paint);
            }
            catch (Exception ex)
            {
                Log.Fatal("Couldn't set property for view with effect ex:" + ex.Message);
            }
        }

        protected override void OnDetached()
        {
            Log.Debug("Android Gradient Effect detached");
        }
    }

    internal class GradientShaderFactory : ShapeDrawable.ShaderFactory
    {
        private readonly Shader.TileMode _tileMode;
        private readonly int[] _colors;
        private readonly float[] _locations;
        private readonly GradientMode _gradientMode;


        internal GradientShaderFactory(int[] colors, float[] locations, Shader.TileMode tileMode,
            GradientMode gradientMode)
        {
            _colors = colors;
            _locations = locations;
            _tileMode = tileMode;
            _gradientMode = gradientMode;
        }

        public override Shader Resize(int width, int height)
        {
            LinearGradient gradient;
            switch (_gradientMode)
                {
                    default:
                        gradient = new LinearGradient(0, 0, width, 0, _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToLeft:
                        gradient = new LinearGradient(width, 0, 0, 0, _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToTop:
                        gradient = new LinearGradient(0, height, 0, 0, _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToBottom:
                        gradient = new LinearGradient(0, 0, 0, height, _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToTopLeft:
                        gradient = new LinearGradient(width, height, 0, 0,
                            _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToTopRight:
                        gradient = new LinearGradient(0, height, width,0 ,
                            _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToBottomLeft:
                        gradient = new LinearGradient(width, 0, 0, height,
                            _colors, _locations,
                            _tileMode);
                        break;
                    case GradientMode.ToBottomRight:
                        gradient = new LinearGradient(0, 0, width, height,
                            _colors,_locations,
                            _tileMode);
                        break;
                }

            return gradient;
        }
    }
}

Answer 7

ここに私が書いた私のContentViewがあります。 CustomRenderなしでPCL/Coreプロジェクトで現状のまま使用できます。ただし、SkiaSharpに依存しています。

ItemTemplateおよびBindableプロパティがあります。

Xamarin Forms Gradient Content View