在后台使用非托管库时无法更新 WPF GUI

发布于 2024-11-01 22:05:59 字数 798 浏览 2 评论 0原文

我在尝试使用 Emgu 从网络摄像头捕获图像时遇到了问题。为了完成此任务，Emgu 使用非托管 opencv 库。所以问题是我无法从 System.Timers.Timer Elapsed 事件更新我的 GUI（WPF 图像控件）。我知道它在不同的线程中运行，但是嘿，这就是我使用调度程序的原因。这是我第一次用 Dispatcher 做不到。收到 InvalidOperationException 并显示“调用线程无法访问此对象，因为另一个线程拥有它。”。我花了一整天的时间寻找解决方案，但仍然无法解决。任何想法为什么会发生？

webcam.OnNewFrame += newBitmapSource => this.imgCaptured.Dispatcher.Invoke
            (
                new Action(delegate
                    {
                        this.imgCaptured.Source = newBitmapSource;
                    }),
                DispatcherPriority.Background
            );

堆栈跟踪上的最后一件事是： System.Windows.Threading.Dispatcher.VerifyAccess()

但是，如果我调用 Dispatcher.CheckAccess() 它会返回 true。

更新：

最后我自己发现了：BitmapSource 必须在 UI 线程上创建。看来它不能以其他方式使用这个对象。

原文

I've enocountered a problem while trying to use Emgu to capture images from a webcam. To do this task, Emgu uses unmanaged opencv libraries. So the problem is that I can't update my GUI (WPF Image control) from System.Timers.Timer Elapsed event. I know it's running in different thread, but hey, that's why I'm using a Dispatcher. It's the first time I can't do it with Dispatcher. Getting InvalidOperationException with "The calling thread cannot access this object because a different thread owns it.". I've spent the whole day searching for a solution, but still couldn't fix it. Any ideas why does it happen?

webcam.OnNewFrame += newBitmapSource => this.imgCaptured.Dispatcher.Invoke
            (
                new Action(delegate
                    {
                        this.imgCaptured.Source = newBitmapSource;
                    }),
                DispatcherPriority.Background
            );

The last thing on Stack Trace is: System.Windows.Threading.Dispatcher.VerifyAccess()

However, if I call Dispatcher.CheckAccess() it returns true.

UPDATE:

Finally I found it out by myself: the BitmapSource had to be created on UI Thread. It seems like it can't use this object otherwise.

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