Добавление градиентного фона в макеты в Xamarin Forms visual studio

Я новичок в формах Xamarin, я создаю ContentPage для меню. Мне нужен цвет линейного градиента на его фоне. Но я не могу найти ссылку, которая расскажет мне, как создать цвет градиента фона. Я также хочу, чтобы это место цвета на фоне кнопки, как селектор в android. Если вы имеете любую информацию, то пожалуйста дайте ответ.

9
c# cross-platform visual-studio-2015 xamarin xamarin.forms

6 ответов

ниже кода мы можем установить горизонтальный и вертикальный градиент (я помещаю его в #region) для любого макета ниже, я пишу для StackLayout если вы хотите написать другой макет, просто замените свой макет на StackLayout.

в PCL:

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);
      }
    }
 }

в XAML:

 <?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>
13

добавьте Skiasharp Nuget в свой проект вместе с этим классом. Используйте его в xaml, где вам нужен градиент.

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);
    }
9

для тех, кто хочет полнофункциональный градиент в Xamarin.Формы приложений, есть мой код:

в вашем PCL

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
    }
}

в вашем проекте iOS

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);
        }
    }
}

в вашем проекте Android

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 GradientLayoutRenderer layout)
                {
                    Colors = layout.Colors;
                    Mode = layout.Mode;
                }
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(@"ERROR:", ex.Message);
            }
        }
    }
}

в UWP проект

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);
            }
        }
    }
}

на страницах XAML

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

    <!-- Your content -->

</renderers:GradientLayout>

надеюсь, это поможет!

7

на данный момент нет реальной функциональности рисования, чтобы сделать это. Вы можете установить изображение в качестве фона, вы можете предоставить много изображений для разных папок (hdpi, mdpi, xhdpi и т. д...) Или вы можете использовать пользовательские средства визуализации чтобы расширить класс ContentPage в свой собственный.

вы можете взглянуть на это обсуждение на форумах Xamarin. https://forums.xamarin.com/discussion/22440/gradient-as-background-color

4

на XFGloss project добавляет возможность добавления градиентов через XAML.

например: 

    <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>
2

чтобы использовать динамические ресурсы, вам придется сделать ваши свойства bindable, как это

    public static BindableProperty StartColorProperty = BindableProperty.Create(nameof(CustomContentPage), typeof(Color), typeof(CustomButton), default(Color), defaultBindingMode: BindingMode.OneWay);

    public Color StartColor
    {
        get { return (Color)GetValue(StartColorProperty); }
        set { SetValue(PaddingProperty, value); }
    }


    public static BindableProperty EndColorProperty = BindableProperty.Create(nameof(CustomContentPage), typeof(Color), typeof(CustomButton), default(Color), defaultBindingMode: BindingMode.OneWay);

    public Color EndColor
    {
        get { return (Color)GetValue(EndColorProperty); }
        set { SetValue(PaddingProperty, value); }
    }
-1