WP8.1 应用程序中的文件选择器没有显示任何照片

Question

我需要制作仪器，允许用户从图库中选择照片。选择照片后，会在 ImageBox 中显示给用户。

问题是，当用户在图库中选择一些照片时，图库关闭，ImageBox 保持为空。代码不返回错误。请帮我找出错误并解决这个问题。谢谢。

这是一个代码：

ImagePath = String.Empty

    filePicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary
        filePicker.ViewMode = PickerViewMode.Thumbnail
        ' Filter to include a sample subset of file types
        filePicker.FileTypeFilter.Clear()
        filePicker.FileTypeFilter.Add(".bmp")
        filePicker.FileTypeFilter.Add(".png")
        filePicker.FileTypeFilter.Add(".jpeg")
        filePicker.FileTypeFilter.Add(".jpg")
        filePicker.PickSingleFileAndContinue()


        Dim BitmapImage = New BitmapImage()
        Await BitmapImage.SetSourceAsync(filePicker)
        MyPhoto.Source = BitmapImage

Answer 1

如果您使用filePicker.PickSingleFileAndContinue()，则需要将代码添加到App_Activated

您会注意到 PickSingleFileAndContinue() 是一个 void 方法，不会返回选择的文件，因为 PickSingleFileAsync() 将返回一个文件。

代码块在C#，对不起，我对vb的了解有限，你可以在下面找到vb示例

Similar SO Answer

C#

FileOpenPicker openPicker = new FileOpenPicker();
openPicker.ViewMode = PickerViewMode.Thumbnail;
openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
openPicker.FileTypeFilter.Add(".jpg");
openPicker.FileTypeFilter.Add(".jpeg");
openPicker.FileTypeFilter.Add(".png");

StorageFile file = await openPicker.PickSingleFileAsync();

当您使用 PickSingleFileAndContinue() 时，您需要实现 ContinuationManager 以获取您选择的文件。

在 App.xaml.cs 中

public ContinuationManager ContinuationManager { get; private set; }

这将在应用程序被激活时触发

    protected async override void OnActivated(IActivatedEventArgs e)
    {
        base.OnActivated(e);

        continuationManager = new ContinuationManager();

        Frame rootFrame = CreateRootFrame();
        await RestoreStatusAsync(e.PreviousExecutionState);

        if(rootFrame.Content == null)
        {
            rootFrame.Navigate(typeof(MainPage));
        }

        var continuationEventArgs = e as IContinuationActivatedEventArgs;
        if (continuationEventArgs != null)
        {
            Frame scenarioFrame = MainPage.Current.FindName("ScenarioFrame") as Frame;
            if (scenarioFrame != null)
            {
                // Call ContinuationManager to handle continuation activation
                continuationManager.Continue(continuationEventArgs, scenarioFrame);
            }
        }

        Window.Current.Activate();
    }

在页面中的使用

假设您的应用的一页包含调用 FileOpenPicker 以选取现有文件的代码。在这个类中，实现来自 ContinuationManager 助手类的相应接口。当您的应用使用 FileOpenPicker 时，要实现的接口是 IFileOpenPickerContinuable。

 public sealed partial class Scenario1 : Page, IFileOpenPickerContinuable
{
    ...

//inside this you have this

private void PickAFileButton_Click(object sender, RoutedEventArgs e)
    {
        ...
        FileOpenPicker openPicker = new FileOpenPicker();
        openPicker.ViewMode = PickerViewMode.Thumbnail;
        openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
        openPicker.FileTypeFilter.Add(".jpg");
        openPicker.FileTypeFilter.Add(".jpeg");
        openPicker.FileTypeFilter.Add(".png");

        // Launch file open picker and caller app is suspended
        // and may be terminated if required
        openPicker.PickSingleFileAndContinue();
    }
}


switch (args.Kind)
    {
        case ActivationKind.PickFileContinuation:
            var fileOpenPickerPage = rootFrame.Content as IFileOpenPickerContinuable;
            if (fileOpenPickerPage != null)
            {
                fileOpenPickerPage.ContinueFileOpenPicker(args as FileOpenPickerContinuationEventArgs);
            }
            break;

        ...
    }

Download msdn sample here

Msdn documentation using FilePicker