c# - Windows Phone 8.1 音乐点击事件

Question

我目前正尝试在单击按钮时播放 mp3 文件，我正在尝试像他那样使用该功能:How can I play mp3 files stored in my Windows Phone 8.1 solution? 但效果不佳，它说

Error   1   The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task'.    c:\users\halt\documents\visual studio 2013\Projects\HDCAR\HDCAR\MainPage.xaml.cs    55  35  HDCAR

代码:

    SystemMediaTransportControls systemControls;
     void Alfa4c_Click(object sender, RoutedEventArgs e)
    {
        // get folder app is installed to
        var installFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
        // get folders mp3 files are installed to.
        var resourcesFolder = await installFolder.GetFolderAsync("Audio");
        // open the mp3 file async
        var audioFile = await mp3FilesFolder.GetFileAsync("Alfa4c.mp3");
        var stream = await audioFile.OpenAsync(Windows.Storage.FileAccessMode.Read);
        // play dat funky music
        MediaElement mediaplayer = new MediaElement();
        mediaplayer.SetSource(stream, audioFile.ContentType);
        mediaplayer.Play();
    }

Answer 1

您需要将其设为async void 方法:

async void Alfa4c_Click(object sender, RoutedEventArgs e)
{
   // Your code...

这允许您在方法中使用 await。

请注意，您可能还想正确处理流。这需要一些额外的工作:

    using(var stream = await audioFile.OpenAsync(Windows.Storage.FileAccessMode.Read))
    {
        // play dat funky music
        MediaElement mediaplayer = new MediaElement();
        mediaplayer.SetSource(stream, audioFile.ContentType);

        var tcs = new TaskCompletionSource<bool>();
        mediaplayer.CurrentStateChanged += (o,e) =>
        {
            if (mediaplayer.CurrentState != MediaElementState.Opening && 
                mediaplayer.CurrentState != MediaElementState.Playing && 
                mediaplayer.CurrentState != MediaElementState.Buffering &&
                mediaplayer.CurrentState != MediaElementState.AcquiringLicense)
                {
                    // Any other state should mean we're done playing
                    tcs.TrySetResult(true);
                }
        };
        mediaplayer.Play();
        await tcs.Task; // Asynchronously wait for media to finish
    }
}