WPF - 无法更改OnChanged方法（从FileSystemWatcher的发射）内的GUI属性 [英] WPF - Cannot change a GUI property inside the OnChanged method (fired from FileSystemWatcher)

问题描述

我想换一个GUI属性的OnChanged方法......（实际上我尝试设置图像源..但这里使用一个按键为简单起见）。这就是所谓的每次FileSystemWatcher的检测文件的改变..它获取到顶输出..但捕捉时，它会尝试设置按钮的宽度异常。

但如果我把相同的代码在一个按钮..它工作得很好。我真心不明白为什么..有人可以帮我吗？

 私人无效调用onChanged（对象源，FileSystemEventArgs E）
 {
 //防止二次烧成，已知的bug为FileSystemWatcher的
试
 {
 _jsonWatcher.EnableRaisingEvents = FALSE; 
 FileInfo的objFileInfo =新的FileInfo（e.FullPath）; 
如果（objFileInfo.Exists！）回报; //忽略文件打开，等待完整的写
 
 //在这里做的东西
 Console.WriteLine（顶）; 
 Test_Button.Width = 500; 
 Console.WriteLine（底部）; 
} 
赶上（例外）
 {
 //什么也不做
} 
终于
 {
 _jsonWatcher.EnableRaisingEvents = TRUE ; 
} 
} 
  

我真正想要做而不是改变一个按钮的宽度：

  BlueBan1_Image.Source = GUI.GetChampImageSource（JSONFile.Get（蓝禁止1），阿凡达 ）; 
  

解决方案

现在的问题是，本次活动是在后台上调线。您需要名帅回调到UI线程：

  //在这里做的东西
 Console.WriteLine（最佳）; 
 this.Dispatcher.BeginInvoke（新动作（（）=> 
 {
 //这个运行在UI线程
 BlueBan1_Image.Source = GUI.GetChampImageSource（JSONFile.Get （蓝禁止1），阿凡达）; 
 Test_Button.Width = 500; 
}））; 
 Console.WriteLine（底部）; 
  

I want to change a GUI property in the OnChanged method... (in actuality im trying to set an image source.. but used a button here for simplicity). This is called everytime filesystemwatcher detects a change in a file.. and it gets to the "top" output.. but catches an exception when it tries to set the button width.

but if i put the same code in a button.. it works just fine. I sincerely don't understand why.. can someone help me?

private void OnChanged(object source, FileSystemEventArgs e)
        {
            //prevents a double firing, known bug for filesystemwatcher
            try
            {
                _jsonWatcher.EnableRaisingEvents = false;
                FileInfo objFileInfo = new FileInfo(e.FullPath);
                if (!objFileInfo.Exists) return;   // ignore the file open, wait for complete write

                //do stuff here                    
                Console.WriteLine("top");
                Test_Button.Width = 500;
                Console.WriteLine("bottom");
            }
            catch (Exception)
            {
                //do nothing
            }
            finally
            {
                _jsonWatcher.EnableRaisingEvents = true;
            }
        }

what i'm really trying to do instead of changing a button width:

BlueBan1_Image.Source = GUI.GetChampImageSource(JSONFile.Get("blue ban 1"), "avatar");

解决方案

The problem is that this event is raised on a background thread. You need to marshal the call back to the UI thread:

// do stuff here                    
Console.WriteLine("top");
this.Dispatcher.BeginInvoke(new Action( () =>
{
    // This runs on the UI thread
    BlueBan1_Image.Source = GUI.GetChampImageSource(JSONFile.Get("blue ban 1"), "avatar");
    Test_Button.Width = 500;
}));
Console.WriteLine("bottom");

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