使用WPF在C＃中异步加载BitmapImage
使用WPF在C＃中异步加载BitmapImage的最佳方法是什么？ 似乎存在许多解决方案，但是存在标准模式还是最佳实践？
谢谢！
我只是在调查这个并且不得不投入我的两分钱，虽然在原始post后几年（以防万一其他人来寻找我正在研究的同样的事情）。
我有一个Image控件，需要使用Stream在后台加载它的图像，然后显示。
我一直遇到的问题是BitmapSource ，它的Stream源和Image控件都必须在同一个线程上。
在这种情况下，使用Binding并将其设置为IsAsynch = true将引发跨线程exception。
BackgroundWorker非常适合WinForms，你可以在WPF中使用它，但我更喜欢避免在WPF中使用WinForm程序集（不建议对项目进行膨胀，这也是一个很好的经验法则）。 在这种情况下，这应该抛出一个无效的交叉引用exception，但我没有测试它。
事实certificate，一行代码将使这些工作中的任何一个：
//Create the image control Image img = new Image {HorizontalAlignment = System.Windows.HorizontalAlignment.Stretch, VerticalAlignment = System.Windows.VerticalAlignment.Stretch}; //Create a seperate thread to load the image ThreadStart thread = delegate { //Load the image in a seperate thread BitmapImage bmpImage = new BitmapImage(); MemoryStream ms = new MemoryStream(); //A custom class that reads the bytes of off the HD and shoves them into the MemoryStream. You could just replace the MemoryStream with something like this: FileStream fs = File.Open(@"C:\ImageFileName.jpg", FileMode.Open); MediaCoder.MediaDecoder.DecodeMediaWithStream(ImageItem, true, ms); bmpImage.BeginInit(); bmpImage.StreamSource = ms; bmpImage.EndInit(); //**THIS LINE locks the BitmapImage so that it can be transported across threads!! bmpImage.Freeze(); //Call the UI thread using the Dispatcher to update the Image control Dispatcher.BeginInvoke(new ThreadStart(delegate { img.Source = bmpImage; img.Unloaded += delegate { ms.Close(); ms.Dispose(); }; grdImageContainer.Children.Add(img); })); }; //Start previously mentioned thread... new Thread(thread).Start(); 假设您正在使用数据绑定，将Binding.IsAsync属性设置为True似乎是实现此目的的标准方法。 如果你使用后台线程在代码隐藏文件中加载位图+ Dispatcher对象是更新UI异步的常用方法
BitmapCacheOption.OnLoad var bmp = await System.Threading.Tasks.Task.Run(() => { BitmapImage img = new BitmapImage(); img.BeginInit(); img.CacheOption = BitmapCacheOption.OnLoad; img.UriSource = new Uri(path); img.EndInit(); ImageBrush brush = new ImageBrush(img); }
要详细说明aku的答案，这里有一个关于在哪里设置IsAsync的小例子：
ItemsSource="{Binding IsAsync=True,Source={StaticResource ACollection},Path=AnObjectInCollection}"
这就是你在XAML中所做的。
这将允许您通过使用HttpClient进行异步下载在UI线程上创建BitmapImage：
private async Task LoadImage(string url) { HttpClient client = new HttpClient(); try { BitmapImage img = new BitmapImage(); img.CacheOption = BitmapCacheOption.OnLoad; img.BeginInit(); img.StreamSource = await client.GetStreamAsync(url); img.EndInit(); return img; } catch (HttpRequestException) { // the download failed, log error return null; } }
使用或扩展System.ComponentModel.BackgroundWorker：
http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx
就个人而言，我发现这是在客户端应用程序中执行异步操作的最简单方法。 （我在WinForms中使用过它，但不是WPF。我假设这也适用于WPF。）
我通常扩展Backgroundworker，但你不必这样做。
public class ResizeFolderBackgroundWorker : BackgroundWorker { public ResizeFolderBackgroundWorker(string sourceFolder, int resizeTo) { this.sourceFolder = sourceFolder; this.destinationFolder = destinationFolder; this.resizeTo = resizeTo; this.WorkerReportsProgress = true; this.DoWork += new DoWorkEventHandler(ResizeFolderBackgroundWorker_DoWork); } void ResizeFolderBackgroundWorker_DoWork(object sender, DoWorkEventArgs e) { DirectoryInfo dirInfo = new DirectoryInfo(sourceFolder); FileInfo[] files = dirInfo.GetFiles("*.jpg"); foreach (FileInfo fileInfo in files) { /* iterate over each file and resizing it */ } } }
这就是你在表单中使用它的方法：
//handle a button click to start lengthy operation private void resizeImageButtonClick(object sender, EventArgs e) { string sourceFolder = getSourceFolderSomehow(); resizer = new ResizeFolderBackgroundWorker(sourceFolder,290); resizer.ProgressChanged += new progressChangedEventHandler(genericProgressChanged); resizer.RunWorkerCompleted += new RunWorkerCompletedEventHandler(genericRunWorkerCompleted); progressBar1.Value = 0; progressBar1.Visible = true; resizer.RunWorkerAsync(); } void genericRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { progressBar1.Visible = false; //signal to user that operation has completed } void genericProgressChanged(object sender, ProgressChangedEventArgs e) { progressBar1.Value = e.ProgressPercentage; //I just update a progress bar }