UI 在图像控件加载 BitmapImage 时冻结

Question

我的 WPF MVVM 应用程序通过Webclient.DownloadFileAsync(url, fileLocation). 该过程顺利进行，下载图片时根本没有冻结。但是当我将图像文件呈现给用户时会出现问题 - 应用程序变得无响应。

下载文件后，我将图像文件分配给 BitmapImage：

public async void LoadFileToBitmapImage(string filePath)

    {

        _isDownloading = false;

        await FileToBitmapImage(filePath);

    }

public Task FileToBitmapImage(string filePath)

    {

        return Task.Run(() =>

        {

            var executableLocation = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);

            var imageLocation = Path.Combine(executableLocation, filePath);

            var bi = new BitmapImage();

            bi.BeginInit();

            bi.UriSource = new Uri(imageLocation);

            bi.EndInit();

            bi.Freeze();

            Image = bi;

        });

    }

图片.cs：

private BitmapImage _image;

public BitmapImage Image

    {

        get => _image;

        set

        {

            _image = value;

            NotifyOfPropertyChange("Image");

        }

    }

XAML 图像绑定：

<Image Source="{Binding Image, IsAsync=True}" Margin="3"/>

下载图像并将其呈现给用户时会出现问题。图像越大，向用户呈现图像所需的时间越多，应用程序无响应的时间就越长。

当应用程序冻结以检查线程并获取以下信息时，我尝试单击暂停，不幸的是它没有为我提供任何信息。

任何帮助都感激不尽！

编辑

值得注意的是，在引发 PropertyChanged 事件之后，应用程序变得无响应，而不是之前。也许这与将图像渲染到 UI 有关？

Answer 1

首先，如果你保存图像，直接将绑定更改为字符串/uri，没有 BitmapImage，不需要创建它，Wpf 为你处理 public BitmapImage Image ===> public Uri Image并删除 FileToBitmapImage。

Answer 2

我花了几天的时间来找到解决这个问题的简单方法。我需要在不冻结 UI 的情况下以高质量显示一百多张图像。我尝试了对绑定等的各种修改，最后只有通过代码和 Source 属性集创建 Image 控件才起作用，然后 Image 出现在界面元素树中。在 XAML 中只有空的 ContentControl：&nbsp; &nbsp; <ContentControl x:Name="ImageContent"/>在代码中：&nbsp; &nbsp; static readonly ConcurrentExclusiveSchedulerPair _pair = new&nbsp; ConcurrentExclusiveSchedulerPair();&nbsp; &nbsp; // Works for very big images&nbsp; &nbsp; public void LoadImage(Uri imageUri)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; var image = new System.Windows.Controls.Image(); // On UI thread&nbsp; &nbsp; &nbsp; &nbsp; RenderOptions.SetBitmapScalingMode(image, BitmapScalingMode.HighQuality);&nbsp; &nbsp; &nbsp; &nbsp; Task.Factory.StartNew(() =>&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var source = new BitmapImage(imageUri); // load ImageSource&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Dispatcher.RunOnMainThread(() =>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; image.Source = source; // Set source while not in UI&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // Add image in UI tree&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ImageContent.Content = image; // ImageContent is empty ContentControl&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ImageContent.InvalidateVisual();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; &nbsp; &nbsp; }, default, TaskCreationOptions.LongRunning, _pair.ExclusiveScheduler);&nbsp; &nbsp; }使用 CacheOption OnLoad 加载图像效果更好。&nbsp; &nbsp; public static ImageSource BitmapFromUri(Uri source)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; if (source == null)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return new BitmapImage(source);&nbsp; &nbsp; &nbsp; &nbsp; using (var fs = new FileStream(source.LocalPath, FileMode.Open))&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var bitmap = new BitmapImage();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; bitmap.BeginInit();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; bitmap.StreamSource = fs;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; bitmap.CacheOption = BitmapCacheOption.OnLoad;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; bitmap.EndInit();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; bitmap.Freeze();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return bitmap;&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }