在UWP应用程序的不同页面运行的后台音频

问题描述：

我想提出一个UWP应用程序，我在一个按钮单击事件中运行的MainPage背景音频。当我移动到另一个网页，还有一个不同的传媒背景音频任务那里踢球。

I am making a UWP App where I run Background Audio in the MainPage on a Button Click event. When I move to another page, there's also a different Media to play in Background Audio Task there.

如何停止当前播放的任务运行的其他？我应该在全球范围界定的东西吗？？关于这个问题的任何帮助。

How can I stop the currently playing Task to run the other? Should I define something globally? Any help regarding this issue?

修改

我使用这个示例： https://github.com/Microsoft/Windows-universal-samples /树/主/样品/ backgroundAudio 虽然第一页是运行的backgroundAudio，我去到第二页和我将用下面的代码一个新的列表中单击事件：

I am using this sample: https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/BackgroundAudio While the backgroundAudio of the first Page is running, I go to the second page and on a click event I set a new List with the following code:

   // First update the persisted start track
   ApplicationSettingsHelper.SaveSettingsValue(ApplicationSettingsConstants.TrackId, RadioFacade.mySongs[0].MediaUri.ToString()); //here
           ApplicationSettingsHelper.SaveSettingsValue(ApplicationSettingsConstants.Position, new TimeSpan().ToString());

                // Start task
                StartBackgroundAudioTask();

但是，新的歌曲的时间比预计时间更运行，并进入该方法的其他：

But the new song takes more than the estimated time to run and enter the else of this method:

private void StartBackgroundAudioTask()
        {
            AddMediaPlayerEventHandlers();

            var startResult = this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                bool result = backgroundAudioTaskStarted.WaitOne(10000);
                //Send message to initiate playback
                if (result == true)
                {
                    MessageService.SendMessageToBackground(new UpdatePlaylistMessage(RadioFacade.mySongs));
                    MessageService.SendMessageToBackground(new StartPlaybackMessage());
                }
                else
                {
                    throw new Exception("Background Audio Task didn't start in expected time");
                }
            });
            startResult.Completed = new AsyncActionCompletedHandler(BackgroundTaskInitializationCompleted);
        }

和旧的（第一弹）的歌曲一直播放。

and the old (first playing) song keeps playing.

我试着用停止当前BackgroundMediaPlayer BackgroundMediaPLayer.Shutdown（），但没有奏效。

I tried to Stop the current BackgroundMediaPlayer using BackgroundMediaPLayer.Shutdown() but it didn't work.

不知道如何让老松站和当前歌曲播放？

Any idea how to let the old song stop and the current song play?

答

可以通过从前景发送消息到它控制背景媒体播放器。例如，

You can control the background media player by sending messages to it from the foreground. For example,

从前台应用程序：

BackgroundMediaPlayer.SendMessageToBackground(new ValueSet
{
    {"playnew", "some value"}
});

在你的后台任务：

public sealed class AudioPlayer : IBackgroundTask
{
    public void Run(IBackgroundTaskInstance taskInstance)
    {
        BackgroundMediaPlayer.MessageReceivedFromForeground += BackgroundMediaPlayer_MessageReceivedFromForeground;
        ...
        ...
    }

    private async void BackgroundMediaPlayer_MessageReceivedFromForeground(object sender, MediaPlayerDataReceivedEventArgs e)
    {
        object value;
        if (e.Data.TryGetValue("playnew", out value) && value != null)
        {
            // value will be whatever you pass from the foreground.
            BackgroundMediaPlayer.Current.Pause();
            BackgroundMediaPlayer.Current.Source = stream source;
            BackgroundMediaPlayer.Current.Play();
        }
    }

    ...
}

playnew可以在你的应用程序中的全局常量。您可以使用ValueSet传递现场直播网址后台任务作为值。

"playnew" can be a global constant in your application. You can use the ValueSet to pass the live stream url to the background task as the value.

在UWP应用程序的不同页面运行的后台音频

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