在预定脚本之前执行映像下载

今天我遇到了这个“有趣”的问题。我在一个wpf窗口上有一个按钮，当我按下它时，我想要一个矩形变为可见并展开到我的主窗口的大小。然后将文本保存在矩形内部以对齐它的中心。发生这种情况后，我希望脚本从网上下载图像以开始执行。不过......当我按下按钮，我的矩形不会成为可见，取而代之的是exe文件开始下载图像...我想代码应该按顺序执行...在预定脚本之前执行映像下载

On button_1 press(blah blah){ 

expander1.IsExpanded = false; //just an expander i use to hide a few elements 

      pleasewait.Visibility = Visibility.Visible; //pleasewait - rectangle 
      plswait_label.Visibility = Visibility.Visible; // plswait_lable - label 
      pleasewait.Height = window_main.Height; 
      pleasewait.Width = window_main.Width; 
      plswait_label.HorizontalAlignment = HorizontalAlignment.Center; 
      plswait_label.VerticalAlignment = VerticalAlignment.Center; 

      image1.Source = null; // dumping previous image before downloading a new one 



//This is the script to download the image and do some other stuff.. 
    string path = System.IO.Path.GetDirectoryName(System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName); 

    Uri urlUri = new Uri(address.Text); 
    var request = WebRequest.CreateDefault(urlUri); 

    byte[] buffer = new byte[4096]; 

    using (var target = new FileStream(path + @"\Temp\br_temp.png", FileMode.Create, FileAccess.Write)) 
    { 
     using (var response = request.GetResponse()) 
     { 
      using (var stream = response.GetResponseStream()) 
      { 
       int read; 

       while ((read = stream.Read(buffer, 0, buffer.Length)) > 0) 
       { 
        target.Write(buffer, 0, read); 
       } 
      } 
     } 
    } 


    Bitmap resizedImage; 
    System.Drawing.Size newSize = new System.Drawing.Size(266, 150); 

    using (System.Drawing.Image originalImage = System.Drawing.Image.FromFile(path + @"\Temp\br_temp.png")) 
     resizedImage = new System.Drawing.Bitmap(originalImage, newSize); 
    resizedImage.Save(path + @"\Temp\temp.png", System.Drawing.Imaging.ImageFormat.Jpeg); 
    resizedImage.Dispose(); 

    BitmapImage MainImage = new BitmapImage(); 
    MainImage.BeginInit(); 
    MainImage.UriSource = new Uri(path + @"\Temp\temp.png"); 
    MainImage.DecodePixelWidth = 266; 
    MainImage.DecodePixelHeight = 150; 
    MainImage.EndInit(); 
    image1.Source = MainImage; 
}

滑稽的是，如果我删除下载代码，矩形实际上做我想要它..

来源

2012-04-28 Meh

下载阻止了UI线程。在下载完成之前，UI上的任何内容都不会起作用。

您需要将下载代码从UI线程中移出。

一个简单的方法做，这是一个BackgroundWorker

像往常一样，我建议你阅读Joe Albahari's ebook

来源

2012-04-28 14:53:08

在预定脚本之前执行映像下载

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