C#W10 UWP BackgroundTask存储文件

问题描述：

我正在尝试在BackgroundTask的C#W10 UWP应用中将图像设置为锁屏或墙纸...在正常执行中，我可以做到这一点，但是当我将相同的代码放入，代码将挂在StorageFile.CreateStreamedFileFromUriAsync.

I'm trying to set an image to lockscreen or wallpaper in my C# W10 UWP app in a BackgroundTask... I can do this just fine in normal execution, but when I put the same code into a BackgroundTask, the code hangs at StorageFile.CreateStreamedFileFromUriAsync.

// See if file exists already, if so, use it, else download it
StorageFile file = null;
try {
    file = await ApplicationData.Current.LocalFolder.GetFileAsync(name);
} catch (FileNotFoundException) {
    if (file == null) {
        Debug.WriteLine("Existing file not found... Downloading from web");

        file = await StorageFile.CreateStreamedFileFromUriAsync(name, uri, RandomAccessStreamReference.CreateFromUri(uri)); // hangs here!!
        file = await file.CopyAsync(ApplicationData.Current.LocalFolder);
    }
}

// Last fail-safe
if (file == null) {
    Debug.WriteLine("File was null -- error finding or downloading file...");
} else {
    // Now set image as wallpaper
    await UserProfilePersonalizationSettings.Current.TrySetLockScreenImageAsync(file);
}

我不知道BackgroundTasks中对StorageFile的任何限制吗?一些谷歌搜索没有产生这样的限制...

Are there any restrictions to StorageFile in BackgroundTasks that I'm unaware of? Some googling yielded no such restrictions...

有什么想法吗?

谢谢.

答

代码挂起"是什么意思?例外?开始操作，但不会完成/返回吗? 我遇到了(或正在解决)类似问题，或者至少我认为这是类似问题.

What does "the code hangs" mean? Exception? Starts the operation but wont finish/return? I had (or have, I'm still working on) a similar problem, or at least I think it's similar.

也许是异步配置上下文问题.

Maybe it's a async-configure-context problem.

//not tested...but try ...AsTask().ConfigureAwait(false):
file = await StorageFile.CreateStreamedFileFromUriAsync(name, uri,    RandomAccessStreamReference.CreateFromUri(uri)).AsTask().ConfigureAwait(false);

启动，但不会返回(未击中下一行代码的断点)，听起来仍然像是SynchronizationContext/Deadlock问题...嗯...

Starts, but wont return (breakpoint on next line of code not hit), sounds still like a SynchronizationContext/Deadlock problem... hmm...

您是否已检查(或确保)CreateStreamedFileFromUriAsync确实完成了?

Have you checked (or make sure) that CreateStreamedFileFromUriAsync really finishes?

C#W10 UWP BackgroundTask存储文件

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