c# - UWP 中的异步绑定(bind)缩略图

Question

我正在我的 UWP 应用中开发内部文件管理器。我通过调用此方法在 GridView 中显示 StorageFolder 的内容:

gridView.ItemsSource = await storageFolder.GetItemsAsync();

此外，我还有一个项目模板，用于可视化链接到 GridView 的文件/文件夹项目外观。我在这个模板中有一个图像对象。我想将 StorageFolder 的缩略图图像绑定(bind)到此 Image 对象的 Source 属性。但是，GetThumbnailAsync() 是一种异步方法，而不是属性。我该怎么做？

Answer 1

Also, I have an item template for visualizing a file/folder item look linked to the the GridView. I have a Image object in this template. I want to bind StorageFolder's thumbnail image to this Image object's Source property.

我觉得你可以先获取缩略图再转成图片，这样可以作为Image的来源吗？控制。我想你需要的是这样的:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Grid.Resources>
        <local:ThumbnailToImageConverter x:Key="cvt" />
    </Grid.Resources>
    <GridView x:Name="gridView">
        <GridView.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <Image Source="{Binding Thumbnail, Converter={StaticResource cvt}}" Stretch="None" />
                    <TextBlock Text="{Binding Name}" Margin="0,5" />
                </StackPanel>
            </DataTemplate>
        </GridView.ItemTemplate>
    </GridView>
</Grid>

绑定(bind)模型的代码隐藏和类:

private ObservableCollection<Model> Collection = new ObservableCollection<Model>();

protected override async void OnNavigatedTo(NavigationEventArgs e)
{
    var files = await KnownFolders.PicturesLibrary.GetFilesAsync();
    foreach (var file in files)
    {
        var thumbnail = await file.GetThumbnailAsync(ThumbnailMode.PicturesView, 100);
        Collection.Add(new Model { Name = file.Name, Thumbnail = thumbnail });
    }
    gridView.ItemsSource = Collection;
}

public class Model
{
    public StorageItemThumbnail Thumbnail { get; set; }
    public string Name { get; set; }
}

代码ThumbnailToImageConverter :

public class ThumbnailToImageConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        BitmapImage image = null;

        if (value != null)
        {
            StorageItemThumbnail thumbnail = (StorageItemThumbnail)value;
            image = new BitmapImage();
            image.SetSource(thumbnail);
        }
        return (image);
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
        throw new NotImplementedException();
    }
}

因为我使用了PicturesLibrary在我的代码中，我们需要启用 <uap:Capability Name="picturesLibrary" />测试此代码时在 list 文件中。