“调用线程无法访问此对象，因为不同的线程拥有它”从 WPF 中的不同线程更新 UI 控件时出现错误

Question

我有从主线程调用的方法。此方法正在创建一个新线程。代码如下所示：

MouseCursorWallObject MouseCursorWall = null;
List<MovingRectangle> MovingRectangles = null;

DrawingImage RenderedImage;


public MainWindow()
    {
        InitializeComponent();
        PrepareObjects();            
        GameLoopRun();                       
    }

private void GameLoopRun()
    {
        Thread thread = new Thread(() =>
        {
            while (true)
            {
                DateTime dtStart = DateTime.Now;

                Events();
                Update();
                Display();

                DateTime dtEnd = DateTime.Now;
                TimeSpan ts = dtEnd - dtStart;
                if (SkipTicks - ts.TotalMilliseconds >= 0)
                {
                    Thread.Sleep((int)(SkipTicks - ts.TotalMilliseconds));
                }
            }
        });
        thread.Start();
    }

在 Display() 方法中，我正在尝试更新图像控件。 “Display()”方法如下所示：

private void Display()
    {
        DrawingGroup imageDrawings = new DrawingGroup();

        // Drawing main canvas
        imageDrawings.Children.Add(DrawingObject(500, 350, 0, 0, new Uri(@"Images\gameCanvas.jpg", UriKind.Relative)));

        // Drawing mouse cursor wall
        imageDrawings.Children.Add(DrawingObject(MouseCursorWall.Width, MouseCursorWall.Height, MouseCursorWall.GetLocX, MouseCursorWall.GetLocY, MouseCursorWall.DisplayTexture));

        for (int i = 0; i < MovingRectangles.Count; i++)
        {
            MovingRectangle o = MovingRectangles[i];

            // Drawing moving object
            imageDrawings.Children.Add(DrawingObject(20, 20, o.GetLocX, o.GetLocY, o.TextureUri));
        }

        if (GamePause == true)
        {

        }
        RenderedImage = new DrawingImage(imageDrawings);

        // Image control on main UI thread
        renderImage.Dispatcher.Invoke(() =>
        {
            renderImage.Source = RenderedImage;
        });
    }

问题是当我尝试使用 Dispatcher.Invoke 更新图像控件时，我收到错误“调用线程无法访问此对象，因为不同的线程拥有它”。我尝试了很多不同的选项，但只有一个可以正常工作：

private void Display()
    {
        this.Dispatcher.Invoke(() => {
            DrawingGroup imageDrawings = new DrawingGroup();

            // Drawing main canvas
            imageDrawings.Children.Add(DrawingObject(500, 350, 0, 0, new Uri(@"Images\gameCanvas.jpg", UriKind.Relative)));

            // Drawing mouse cursor wall
            imageDrawings.Children.Add(DrawingObject(MouseCursorWall.Width, MouseCursorWall.Height, MouseCursorWall.GetLocX, MouseCursorWall.GetLocY, MouseCursorWall.DisplayTexture));

            for (int i = 0; i < MovingRectangles.Count; i++)
            {
                MovingRectangle o = MovingRectangles[i];

                // Drawing moving object
                imageDrawings.Children.Add(DrawingObject(20, 20, o.GetLocX, o.GetLocY, o.TextureUri));
            }

            if (GamePause == true)
            {

            }

            RenderedImage = new DrawingImage(imageDrawings);
            renderImage.Source = RenderedImage;
        });

    }

你能解释一下为什么“Display()”方法的第二个选项可以正常工作，但第一个选项会抛出异常吗？我做错了什么？

Answer 1

DrawingImage 和DrawingGroup 都继承自DispatcherObject，这意味着它们需要从创建它们的线程中访问。这就是为什么您的所有工作都被调用回调度程序的版本可以正常工作的原因。

正如 Brian Reichle 所指出的，这些对象也继承自 System.Windows.Freezable，您可以利用它来允许跨线程访问对象。