Windows UWP C＃代码可在台式机上使用，而不能在移动设备上使用

Question

我正在尝试使用C＃更改桌面和Windows Mobile的背景墙纸。 一切都可以在台式机上运行，​​但不能在Windows Mobile中运行。 我只是有一个带有Click事件的按钮，该事件执行ChangeBackground：

private async void ChangeBackgroundButton_Click(object sender, RoutedEventArgs e)
{
    await ChangeBackground();
    updateTask();
}

private static async Task ChangeBackground()
{
    if (UserProfilePersonalizationSettings.IsSupported())
    {
        StorageFile file = Task.Run(async () => {
            Uri uri = new Uri("https://source.unsplash.com/random/1080x1920");
            StorageFile f = await StorageFile.CreateStreamedFileFromUriAsync("background.jpg", uri, RandomAccessStreamReference.CreateFromUri(uri));
            return await f.CopyAsync(ApplicationData.Current.LocalFolder, "background.jpg", NameCollisionOption.ReplaceExisting);
            }).Result;
        UserProfilePersonalizationSettings settings = UserProfilePersonalizationSettings.Current;
        await settings.TrySetWallpaperImageAsync(file);
    }
}

当我按Windows Mobile上的按钮时，该应用程序卡住了。 该按钮保持悬停状态，并且墙纸没有变化。

我究竟做错了什么？

编辑：我重写了代码以解决CopyAsync的问题。 现在的代码如下所示：

    private static async Task<StorageFile> ChangeBackground()
    {
        if (UserProfilePersonalizationSettings.IsSupported())
        {
            Uri uri = new Uri("https://source.unsplash.com/random/1920x1080");
            string filename = DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".jpg";

            HttpClient httpClient = new HttpClient();
            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, uri);
            HttpResponseMessage response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

            var imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
            var fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite);
            DataWriter writer = new DataWriter(fs.GetOutputStreamAt(0));
            writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
            await writer.StoreAsync();
            writer.DetachStream();
            await fs.FlushAsync();

            StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(filename);

            UserProfilePersonalizationSettings settings = UserProfilePersonalizationSettings.Current;
            if (!await settings.TrySetWallpaperImageAsync(file))
            {
                Debug.WriteLine("Failed");
            } else
            {
                Debug.WriteLine("Success");
            }
            return file;
        }
        return null;
    }

在Windows 10上显示成功，在Windows 10 Mobile上显示失败。

Answer 1

只需使用ChangeBackground函数中的await自然地编写代码； 无需使用Task.Run ，然后获取它的Result （这将导致死锁）。

Answer 2

就像我昨天说的那样，我无法弄清楚为什么CopyAsync()方法在移动设备上运行时会卡在您的第一个代码中。 使用Http下载图片是正确的，但是第二个代码中存在一些问题，即使在我这边的PC上也无法使用。

很明显，您不能使用httpClient.SendAsync()从uri获取数据。 这是我的代码：

private static async Task ChangeBackground()
{
    if (UserProfilePersonalizationSettings.IsSupported())
    {
        Uri uri = new Uri("https://source.unsplash.com/random/1920x1080");
        using (HttpClient client = new HttpClient())
        {
            try
            {
                HttpResponseMessage response = await client.GetAsync(uri);
                if (response != null && response.StatusCode == HttpStatusCode.Ok)
                {
                    string filename = "background.jpg";
                    var imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
                    using (IRandomAccessStream stream = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
                    {
                        await response.Content.WriteToStreamAsync(stream);
                    }
                    StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(filename);
                    UserProfilePersonalizationSettings settings = UserProfilePersonalizationSettings.Current;
                    if (!await settings.TrySetWallpaperImageAsync(file))
                    {
                        Debug.WriteLine("Failed");
                    }
                    else
                    {
                        Debug.WriteLine("Success");
                    }
                }
            }
            catch
            {
            }
        }
    }
}

顺便说一句，我正在使用Windows.Web.Http API，而不是System.Net.Http API。