如何在Windows Universal App中显示网络文件夹或本地驱动器中的图像

Question

I'm having trouble displaying an jpg in an Image control in a Windows Universal App. (I had the same problem trying to create a Windows 8 Store app as well)

I have a simple form with an Image control on it. All I want to do is be able to open images in a folder on my local drive or a network drive on my local network and display them. But I am not having any luck. The only thing I get is E_NETWORK_ERROR, with no additional information.

I assume it probably has something to do with security, but surely there must be a setting or permission to allow me to do it. I tried enabling Private Networks in the Capabilities tab of the manifest, but that didn't help. I don't see anything in Declarations that sounds like what I need.

I know UWP apps are somewhat sandboxed, but if you can't even access local files, what good are they?

Here is a sample of code I have tried. I've done other iterations as well, but they all have the same end result.

Xaml:

<Image Name="Image1"/>

Code behind:

    public LoadImage()
    {
        var bitmap = new BitmapImage();
        bitmap.ImageFailed += Bitmap_ImageFailed;
        bitmap.UriSource = new Uri(@"D:\Users\Steve\Documents\SomeImage.JPG", UriKind.Absolute);
        Image1.Source = bitmap;
    }

    private void Bitmap_ImageFailed(object sender, ExceptionRoutedEventArgs e)
    {
        Debug.Write(e.ErrorMessage);
    }

When I run it, I end up in the Bitmap_ImageFailed event and the ErrorMessage property is simply "E_NETWORK_ERROR", and nothing is displayed in the Image. Not very helpful.

What am I missing? It has to be something simple and obvious that I am overlooking.

Update:

Thanks to all the suggestions here I was able to get it going. The part I was failing to get through my skull was that you can't just give it a folder and expect it to read a file, even as a "quick & dirty test". You have to go through "proper channels" to get there. I pieced it all together and came up with this example which displays the first image in the selected folder:

    private async void Button_Click(object sender, RoutedEventArgs e)
    {
        FolderPicker folderPicker = new FolderPicker();
        folderPicker.SuggestedStartLocation = PickerLocationId.Desktop;
        folderPicker.FileTypeFilter.Add(".jpg");
        folderPicker.FileTypeFilter.Add(".tif");
        folderPicker.FileTypeFilter.Add(".png");

        StorageFolder folder = await folderPicker.PickSingleFolderAsync();
        if (folder != null)
        {
            StorageApplicationPermissions.FutureAccessList.AddOrReplace("PickedFolderToken", folder);
            var files = await folder.GetFilesAsync();

            var bitmap = new BitmapImage();
            bitmap.ImageFailed += Bitmap_ImageFailed;
            var stream = await files.First().OpenReadAsync();
            await bitmap.SetSourceAsync(stream);
            Image1.Source = bitmap;
        }
    }

In addition, I had to add the file types for .jpg, .tif and .png as well as File Open Picker to the Declarations.

Answer 1

You can figure out all necessary information in MSDN article File access permissions

In addition to the default locations, an app can access additional files and folders by declaring capabilities in the app manifest (see App capability declarations ), or by calling a file picker to let the user pick files and folders for the app to access (see Open files and folders with a picker ).

So if you want to read a file from users document folder you need to update your applications AppXManifest to request the Document Library Access capability .

You also need to update your AppXManifest by declaring what file type(s) you want to access. Then, even with access to the folders, you only have access to a limited set of file types. You have to specify supported files types on Declarations tab

I set a new file type (.txt) and let it role from there. And code example

async void Button_Click_2(object sender, RoutedEventArgs e)
{
    var _Name = "HelloWorld.txt";
    var _Folder = KnownFolders.DocumentsLibrary;
    var _Option = Windows.Storage.CreationCollisionOption.ReplaceExisting;

    // create file 
    var _File = await _Folder.CreateFileAsync(_Name, _Option);

    // write content
    var _WriteThis = "Hello world!";
    await Windows.Storage.FileIO.WriteTextAsync(_File, _WriteThis);

    // acquire file
    try { _File = await _Folder.GetFileAsync(_Name); }
    catch (FileNotFoundException) { /* TODO */ }

    // read content
    var _Content = await FileIO.ReadTextAsync(_File);
    await new Windows.UI.Popups.MessageDialog(_Content).ShowAsync();
}