DrawingVisual未刷新

发布于 2024-08-09 22:20:30 字数 1704 浏览 2 评论 0原文

我创建自己的 FrameworkElement 并通过返回我自己的 DrawingVisual 覆盖 VisualChildrenCount{get;} 和 GetVisualChild(int index) > 实例。

如果我在初始渲染（例如在计时器处理程序中）后使用 DrawingVisual.RenderOpen() 修改视觉内容并绘制到上下文中，则该元素不会刷新。

这是最简单的示例：

using System;
using System.Windows;
using System.Windows.Media;
using System.Windows.Threading;

namespace VisualTest
{
    public class TestControl : FrameworkElement
    {
        private readonly DrawingVisual _visual = new DrawingVisual();

        public TestControl()
        {
            Draw(false);

            var timer = new DispatcherTimer {Interval = new TimeSpan(0, 0, 2)};
            timer.Tick += (sender, args) =>
                              {
                                  Draw(true);
                                  InvalidateVisual();
                                  timer.Stop();
                              };
            timer.Start();
        }

        protected override Visual GetVisualChild(int index)
        {
            return _visual;
        }

        protected override int VisualChildrenCount
        {
            get { return 1; }
        }

        private void Draw(bool second)
        {
            DrawingContext ctx = _visual.RenderOpen();
            if (!second)
                ctx.DrawRoundedRectangle(Brushes.Green, null, new Rect(0, 0, 200, 200), 20, 20);
            else
                ctx.DrawEllipse(Brushes.Red, null, new Point(100, 100), 100, 100);
            ctx.Close();
        }
    }
}

InvalidateVisual() 不执行任何操作。尽管如果您调整包含该元素的窗口的大小，它也会更新。

关于如何正确刷新内容有什么想法吗？最好不为我的元素引入新的依赖属性。

原文

I create my own FrameworkElement and override VisualChildrenCount{get;} and GetVisualChild(int index) by returning my own DrawingVisual instance.

If I modify the content of the visual after initial rendering (e.g. in timer handler) using DrawingVisual.RenderOpen() and drawing into the context, the element is not refreshed.

Here's the simplest sample:

using System;
using System.Windows;
using System.Windows.Media;
using System.Windows.Threading;

namespace VisualTest
{
    public class TestControl : FrameworkElement
    {
        private readonly DrawingVisual _visual = new DrawingVisual();

        public TestControl()
        {
            Draw(false);

            var timer = new DispatcherTimer {Interval = new TimeSpan(0, 0, 2)};
            timer.Tick += (sender, args) =>
                              {
                                  Draw(true);
                                  InvalidateVisual();
                                  timer.Stop();
                              };
            timer.Start();
        }

        protected override Visual GetVisualChild(int index)
        {
            return _visual;
        }

        protected override int VisualChildrenCount
        {
            get { return 1; }
        }

        private void Draw(bool second)
        {
            DrawingContext ctx = _visual.RenderOpen();
            if (!second)
                ctx.DrawRoundedRectangle(Brushes.Green, null, new Rect(0, 0, 200, 200), 20, 20);
            else
                ctx.DrawEllipse(Brushes.Red, null, new Point(100, 100), 100, 100);
            ctx.Close();
        }
    }
}

InvalidateVisual() does nothing. Although if you resize the window containing the element, it gets updated.

Any ideas on how to properly refresh the content? Preferably without introducing new dependency properties for my element.

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御守 2024-08-16 22:20:30

添加

this.AddVisualChild(_visual);
this.AddLogicalChild(_visual);

到 TestControl 类构造函数。

Add

this.AddVisualChild(_visual);
this.AddLogicalChild(_visual);

to TestControl class constructor.

回复收藏 0 原文

酒绊 2024-08-16 22:20:30

基于SMART_n的回答，这里有一个改进的解决方案，不会泄漏内存：

    public TestControl()
    {
        Loaded += AddVisualToTree;
        Unloaded += RemoveVisualFromTree;

        Draw(false);

        var timer = new DispatcherTimer {Interval = new TimeSpan(0, 0, 2)};
        timer.Tick += (sender, args) =>
                          {
                              Draw(true);
                              InvalidateVisual();
                              timer.Stop();
                          };
        timer.Start();

    }

    private void AddVisualToTree(object sender, RoutedEventArgs e)
    {
        AddVisualChild(_visual);
        AddLogicalChild(_visual);
    }

    private void RemoveVisualFromTree(object sender, RoutedEventArgs e)
    {
        RemoveLogicalChild(_visual);
        RemoveVisualChild(_visual);
    }

Based on SMART_n's answer, here is an improved solution that doesn't leak memory:

    public TestControl()
    {
        Loaded += AddVisualToTree;
        Unloaded += RemoveVisualFromTree;

        Draw(false);

        var timer = new DispatcherTimer {Interval = new TimeSpan(0, 0, 2)};
        timer.Tick += (sender, args) =>
                          {
                              Draw(true);
                              InvalidateVisual();
                              timer.Stop();
                          };
        timer.Start();

    }

    private void AddVisualToTree(object sender, RoutedEventArgs e)
    {
        AddVisualChild(_visual);
        AddLogicalChild(_visual);
    }

    private void RemoveVisualFromTree(object sender, RoutedEventArgs e)
    {
        RemoveLogicalChild(_visual);
        RemoveVisualChild(_visual);
    }

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