BitmapImage ImageOpened 事件未触发

Question

为什么在此示例中未触发 ImageOpened 事件？我在 Win8 的 WinRT 应用程序中使用它。

BitmapImage myImage = new BitmapImage();        
myImage.ImageOpened += myImage_ImageOpened;
myImage.UriSource = new Uri("ms-appx:/Assets/Image.png");


private void myImage_ImageOpened(object sender, RoutedEventArgs e)
{
    int pixelHeight = (sender as BitmapImage).PixelHeight;
}

我的问题是 ImageOpened 事件没有被触发。我想检查图像的 PixelHeight 和 PixelWidth，但如果没有收到此事件，则无法检查。

Answer 1

WinRT 具有延迟加载行为。除非您实际显示图像，否则不会加载图像。如果您确实需要强制加载以执行一些布局调整，您可以使用这种解决方法来强制加载：

 private async void Download()
    {
        Windows.UI.Xaml.Media.Imaging.BitmapImage image = new Windows.UI.Xaml.Media.Imaging.BitmapImage();
        image.ImageFailed += image_ImageFailed;
        image.ImageOpened += image_ImageOpened;
        var file = await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appx:///Assets/Logo.scale-100.png", UriKind.Absolute));
        var stream = await file.OpenStreamForReadAsync();
        await image.SetSourceAsync(stream.AsRandomAccessStream());
    }

    void image_ImageFailed(object sender, ExceptionRoutedEventArgs e)
    {
        MessageDialog dg = new MessageDialog("Image Failed");
        dg.ShowAsync();
    }

    void image_ImageOpened(object sender, RoutedEventArgs e)
    {
        MessageDialog dg = new MessageDialog("Image Opened");
        dg.ShowAsync();
    }