wpf 自定义绘图元素

1 新建wpf项目

2 新建wpf UserControl类库

3 在类库中新建类，继承于FrameworkElement

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace CustomControl
{
    public class CustomDrawnElement : FrameworkElement
    {
        static CustomDrawnElement()
        {
            FrameworkPropertyMetadata metadata = new FrameworkPropertyMetadata(Colors.Yellow);
            metadata.AffectsRender = true;
            BackgroundColorProperty = DependencyProperty.Register("BackgroundColor",
                typeof(Color), typeof(CustomDrawnElement), metadata);
        }

        public Color BackgroundColor
        {
            get { return (Color)GetValue(BackgroundColorProperty); }
            set { SetValue(BackgroundColorProperty, value); }
        }

        public static readonly DependencyProperty BackgroundColorProperty;

        protected override void OnMouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);
            this.InvalidateVisual();
        }

        protected override void OnMouseLeave(MouseEventArgs e)
        {
            base.OnMouseLeave(e);
            this.InvalidateVisual();
        }


        protected override void OnRender(DrawingContext drawingContext)
        {
            base.OnRender(drawingContext);

            Rect bounds = new Rect(0, 0, base.ActualWidth, base.ActualHeight);
            drawingContext.DrawRectangle(GetForegroundBrush(), null, bounds);
        }

        private Brush GetForegroundBrush()
        {
            if (!IsMouseOver)
            {
                return new SolidColorBrush(BackgroundColor);
            }
            else
            {
                RadialGradientBrush brush = new RadialGradientBrush(Colors.White, BackgroundColor);
                Point absoluteGradientOrigin = Mouse.GetPosition(this);
                Point relativeGradientOrigin = new Point(
                    absoluteGradientOrigin.X / base.ActualWidth, absoluteGradientOrigin.Y / base.ActualHeight);

                brush.GradientOrigin = relativeGradientOrigin;
                brush.Center = relativeGradientOrigin;
                brush.Freeze();
                return brush;
            }
        }
    }
}

4 主程序

<Window x:Class="CustomControlApp.CustomDrawnElementTest"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:CustomControlApp"
        xmlns:lib="clr-namespace:CustomControl;assembly=CustomControl"
        mc:Ignorable="d"
        Title="CustomDrawnElementTest" Height="450" Width="800">
    <Grid Margin="5">
        <Grid.RowDefinitions>
            <RowDefinition></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>
        <lib:CustomDrawnElement BackgroundColor="{Binding ElementName=lstColors,Path=SelectedItem.Content}"></lib:CustomDrawnElement>

        <StackPanel Grid.Row="1" Orientation="Horizontal" Margin="5">
            <TextBlock VerticalAlignment="Center" xml:space="preserve">Background Color:</TextBlock>
            <ComboBox Name="lstColors" Width="100">
                <ComboBoxItem>Yellow</ComboBoxItem>
                <ComboBoxItem>Blue</ComboBoxItem>
                <ComboBoxItem IsSelected="True">Green</ComboBoxItem>
            </ComboBox>
        </StackPanel>
    </Grid>
</Window>