Windows UWP C# 代码适用于桌面，不适用于移动设备

Question

我正在尝试使用 C# 更改桌面和 Windows 移动设备的背景墙纸。在桌面上一切正常，但在 Windows 移动设备上却不行。我只有一个带有执行 ChangeBackground 的单击事件的按钮：

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);
    }
}

当我在 Windows 移动设备上按下按钮时，应用程序卡住了。按钮保持悬停状态，壁纸不变。

我做错了什么？

编辑：我重写了代码以修复 CopyAsync 的问题。代码现在看起来像这样：

    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

只需在 ChangeBackground 函数中使用 await 自然地编写您的代码；没有必要使用 Task.Run 然后获取它的 Result （这会导致死锁）。

Answer 2

正如我昨天所说，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下载图片是对的，但是你的第二段代码有问题，我这边的pc上也不能用

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
            {
            }
        }
    }
}

顺便说一下，我使用的是 Windows.Web.Http API，而不是 System.Net.Http API。

Windows UWP C# 代码适用于桌面，不适用于移动设备

Windows UWP C# code works on desktop, not on mobile

c#

windows-10

windows-10-mobile

uwp