如何通过C#寻找MediaPlayerElement

Question

我正在为 MediaPlayerElement 创建 CustomMediaTransportControls。在其中，我添加了一个新按钮，用于使用 CompactOverlay Mode 中当前正在播放的视频创建 window。我使用下面的代码完成了它。

//Button click event for CompactOverlayButton to Create a Frame in CompactOverlay mode
public async void CompactOverlayButton_ClickAsync(object sender, RoutedEventArgs e)
{
    int compactViewId = ApplicationView.GetForCurrentView().Id;      //Initializing compactViewId to the Current View ID
    await CoreApplication.CreateNewView().Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        var frame = new Frame();
        compactViewId = ApplicationView.GetForCurrentView().Id;
        frame.Navigate(typeof(VideoPlayerPage));
        Window.Current.Content = frame;
        Window.Current.Activate();
        ApplicationView.GetForCurrentView().Title = "";
    });
    bool viewShown = await ApplicationViewSwitcher.TryShowAsViewModeAsync(compactViewId, ApplicationViewMode.CompactOverlay);
    compactOverlayButton.Visibility = Visibility.Collapsed;
}

但一个问题是我想从用户单击 CompactOverlay 按钮的位置恢复视频。我该怎么做？

Answer 1

我认为您的问题的一种可能解决方案是使用 Navigate(TypeName, Object) method to pass the current playback position to your VideoPlayerPage and in VideoPlayerPage code-behind file, override the OnNavigatedTo 方法从当前播放位置恢复视频。

例如，假设当前页面中有两个名为 "mediaPlayerElement" 的 MediaPlayerElement 和 VideoPlayerPage。在当前页面，我们可以将当前播放位置传给pass the current playback position，如下：

//Get current playback position
var position = mediaPlayerElement.MediaPlayer.PlaybackSession.Position;

int compactViewId = 0;
await CoreApplication.CreateNewView().Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
    var frame = new Frame();
    compactViewId = ApplicationView.GetForCurrentView().Id;
    frame.Navigate(typeof(VideoPlayerPage), position);
    Window.Current.Content = frame;
    Window.Current.Activate();
    ApplicationView.GetForCurrentView().Title = "";
});
bool viewShown = await ApplicationViewSwitcher.TryShowAsViewModeAsync(compactViewId, ApplicationViewMode.CompactOverlay);

然而，CompactOverlayButton_ClickAsync 是 CustomMediaTransportControls 中的一个函数，它是 MediaTransportControls 的派生 class。从这里我们无法得到 mediaPlayerElement。所以我们需要在这里做一些修改。

在自定义传输控件中添加自定义命令按钮时，我们通常会使用public EventHandler 来执行单击按钮时发生的操作。有关详细信息，请参阅 Adding a custom button in Create custom transport controls.

在这种情况下，我们可以添加一个EventHandler，例如：

public event EventHandler<EventArgs> CompactOverlaid;
...
//Button click event for CompactOverlayButton to Create a Frame in CompactOverlay mode
public void CompactOverlayButton_Click(object sender, RoutedEventArgs e)
{               
    CompactOverlaid?.Invoke(this, EventArgs.Empty);
    compactOverlayButton.Visibility = Visibility.Collapsed;
}

并且在当前页面中，使用 CustomMediaTransportControls 如：

<local:CustomMediaTransportControls x:Name="CustomMediaControl"  CompactOverlaid="CustomMediaControl_CompactOverlaid"/>

private async void CustomMediaControl_CompactOverlaid(object sender, EventArgs e)
{
    //Get current playback position
    var position = mediaPlayerElement.MediaPlayer.PlaybackSession.Position;

    int compactViewId = 0;
    await CoreApplication.CreateNewView().Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        var frame = new Frame();
        compactViewId = ApplicationView.GetForCurrentView().Id;
        frame.Navigate(typeof(VideoPlayerPage), position);
        Window.Current.Content = frame;
        Window.Current.Activate();
        ApplicationView.GetForCurrentView().Title = "";
    });
    bool viewShown = await ApplicationViewSwitcher.TryShowAsViewModeAsync(compactViewId, ApplicationViewMode.CompactOverlay);
}

然后在 VideoPlayerPage 代码隐藏文件中，重写 OnNavigatedTo 方法，如下所示：

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    /// set media source
    ...
    /// set media source

    if (e.Parameter is TimeSpan position)
    {
        mediaPlayerElement.MediaPlayer.PlaybackSession.Position = position;
    }

    mediaPlayerElement.MediaPlayer.Play();
}

在此之后，视频应该可以从用户点击的位置播放 CompactOverlayButton。

如何通过C#寻找MediaPlayerElement

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