PlayToSource 类

定义

命名空间:

Windows.Media.PlayTo

表示连接到“播放到”目标的媒体元素。

public ref class PlayToSource sealed

/// [Windows.Foundation.Metadata.ContractVersion(Windows.Foundation.UniversalApiContract, 65536)]
/// [Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
/// [Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
/// [Windows.Foundation.Metadata.Deprecated("PlayToSource may be altered or unavailable for releases after Windows 10. Instead, use CastingSource.", Windows.Foundation.Metadata.DeprecationType.Deprecate, 65536, "Windows.Foundation.UniversalApiContract")]
class PlayToSource final

[Windows.Foundation.Metadata.ContractVersion(typeof(Windows.Foundation.UniversalApiContract), 65536)]
[Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
[Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
[Windows.Foundation.Metadata.Deprecated("PlayToSource may be altered or unavailable for releases after Windows 10. Instead, use CastingSource.", Windows.Foundation.Metadata.DeprecationType.Deprecate, 65536, "Windows.Foundation.UniversalApiContract")]
public sealed class PlayToSource

Public NotInheritable Class PlayToSource

继承

Object Platform::Object IInspectable PlayToSource

属性

ContractVersionAttribute DeprecatedAttribute MarshalingBehaviorAttribute ThreadingAttribute

Windows 要求

设备系列	Windows 10 (在 10.0.10240.0 中引入)
API contract	Windows.Foundation.UniversalApiContract (在 v1.0 中引入)

示例

IReadOnlyList<Windows.Storage.StorageFile> imageList;   // contains the list of images to show
bool streaming = false;      // true when streaming using Play To; otherwise false
int timeLapse = 5;           // time between images (5 seconds)
int imageSize = 600;         // size of current displayed image
int thumbnailSize = 200;     // size of "thumbnail" of next image
int currentImage = 0;        // index of the current image from imageList

// Get the list of images from the Pictures folder and start the slide show.
async private void StartSlideShow()
{
    var resultsLibrary = await
        Windows.Storage.KnownFolders.PicturesLibrary.GetFilesAsync();
    imageList = resultsLibrary;
    if (imageList.Count > 0)
    {
        var image = QueueImage(0, true);
    }
    else
    {
        MessageBlock.Text = "There are no images in the Pictures library.";
    }
}

// PlayNextImage
// Called when a new image is displayed due to a timeout.
// Removes the current image object and queues a new next image.
// Sets the next image index as the new current image, and increases the size 
// of the new current image. Then sets the timeout to display the next image.

private async void PlayNextImage(int num)
{
    // Stop the timer to avoid repeating.
    if (timer != null) { timer.Stop(); }

    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        async () =>
        {
            SlideShowPanel.Children.Remove((UIElement)(SlideShowPanel.FindName("image" + num)));
            var i = await QueueImage(num + 2, false);

            currentImage = num + 1;
            ((Image)SlideShowPanel.FindName("image" + currentImage)).Width = imageSize;
        });

    timer = new Windows.UI.Xaml.DispatcherTimer();
    timer.Interval = new TimeSpan(0, 0, timeLapse);
    timer.Tick += delegate(object sender, object e)
    {
        PlayNextImage(num + 1);
    };
    timer.Start();
}

// QueueImage
// Called to create an image object for the displayed images.

private async System.Threading.Tasks.Task<Image> QueueImage(int num, bool isFirstImage)
{
    // Create the image element for the specified image index and add to the
    // slide show div.

    Image image = new Image();
    image.Width = isFirstImage ? imageSize : thumbnailSize;
    image.Name = "image" + num;
    image.VerticalAlignment = VerticalAlignment.Bottom;
    var fileContents = await imageList[num % imageList.Count].OpenReadAsync();
    var imageBitmap = new Windows.UI.Xaml.Media.Imaging.BitmapImage();
    imageBitmap.SetSource(fileContents);
    image.Source = imageBitmap;

    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        () =>
        {
            SlideShowPanel.Children.Add(image);
        });

    // If this is the first image of the slide show, queue the next image. Do
    // not queue if streaming as images are already queued before
    // streaming using Play To.

    if (isFirstImage && !streaming)
    {
        var i = await QueueImage(num + 1, false);

        timer = new Windows.UI.Xaml.DispatcherTimer();
        timer.Interval = new TimeSpan(0, 0, timeLapse);
        timer.Tick += delegate(object sender, object e)
        {
            PlayNextImage(num);
        };
        timer.Start();
    }

    // Use the transferred event of the Play To connection for the current image object
    // to "move" to the next image in the slide show. The transferred event occurs
    // when the PlayToSource.playNext() method is called, or when the Play To
    // Receiver selects the next image.

    image.PlayToSource.Connection.Transferred += 
        async delegate(Windows.Media.PlayTo.PlayToConnection sender, 
                 Windows.Media.PlayTo.PlayToConnectionTransferredEventArgs e)
           { 
               currentImage = num + 1;

               await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                   () =>
                   {
                       ((Image)SlideShowPanel.FindName("image" + currentImage)).Width = imageSize;
                   });
           };


// Use the statechanged event to determine which action to take or to respond
// if the Play To Receiver is disconnected.
image.PlayToSource.Connection.StateChanged += 
    async delegate(Windows.Media.PlayTo.PlayToConnection sender,
             Windows.Media.PlayTo.PlayToConnectionStateChangedEventArgs e)
    {
        switch (e.CurrentState) {
            case Windows.Media.PlayTo.PlayToConnectionState.Disconnected:

                // If the state is disconnected and the current image index equals the 
                // num value passed to queueImage, then the image element is not connected 
                // to the Play To Receiver any more. Restart the slide show.
                // Otherwise, the current image has been discarded and the slide show
                // has moved to the next image. Clear the current image object and
                // remove it from the slide show div.

                if (currentImage == num)
                {
                    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, 
                        async () =>
                        {
                            MessageBlock.Text = "Slideshow disconnected";

                            // Cancel any existing timeout
                            if (timer != null) { timer.Stop(); }

                            // Clear all image objects from the slide show div
                            SlideShowPanel.Children.Clear();

                            // Reset the slide show objects and values to their beginning state
                            streaming = false;
                            DisconnectButton.Visibility = Visibility.Collapsed;
                            InstructionsBlock.Visibility = Visibility.Visible;
                            DisconnectButton.Click -= DisconnectButtonClick;

                            // Restart the slide show from the current image index
                            var i = await QueueImage(currentImage, true);
                        });
                } 
                else 
                { 
                    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                            () =>
                            {
                                image.PlayToSource.Next = null;

                                if (streaming)
                                {
                                    SlideShowPanel.Children.Remove(image);
                                }   
                            });
                }

                break;
            
            case Windows.Media.PlayTo.PlayToConnectionState.Connected:

                // If the state is connected and the previous state is disconnected, 
                // then the image element is newly connected. Queue up the next image so 
                // that it is loaded while the current image is being displayed.
                // If the previous state is rendering, then the user has paused the slideshow 
                // on the Play To Receiver. Clear the current timeout until the user restarts
                // the slide show.
                await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                    async () =>
                    {
                        if (e.PreviousState ==  Windows.Media.PlayTo.PlayToConnectionState.Disconnected)
                        {
                            var imageNext = await QueueImage(num + 1, false);
                            image.PlayToSource.Next = imageNext.PlayToSource;
                        } 
                        else if (e.PreviousState == Windows.Media.PlayTo.PlayToConnectionState.Rendering) 
                        {
                            if (timer != null) { timer.Stop(); }
                        }

                        if (currentImage == num) 
                        {
                            MessageBlock.Text = "Slideshow connected";
                        }
                    });
                break;

            case  Windows.Media.PlayTo.PlayToConnectionState.Rendering:

                // If the state is rendering and the previous state is
                // connected, then the Play To Receiver has restarted
                // the slide show.
                    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                        () =>
                        {
                            if (e.PreviousState == Windows.Media.PlayTo.PlayToConnectionState.Connected)
                            {
                                // Clear any existing timeout.
                                if (timer != null) { timer.Stop(); }

                                // Restart the slide show.
                                timer = new Windows.UI.Xaml.DispatcherTimer();
                                timer.Interval = new TimeSpan(0, 0, timeLapse);
                                timer.Tick += delegate(object s, object args)
                                {
                                    image.PlayToSource.PlayNext();
                                };
                                timer.Start();
                            }

                            if (currentImage == num)
                            {
                                MessageBlock.Text = "Slideshow rendering";
                            }
                       }); 
                break;
            }
        };

    return image;
}

Private imageList As IReadOnlyList(Of Windows.Storage.StorageFile)    ' contains the list of images to show
Private streaming As Boolean = False       ' true when streaming using Play To otherwise false
Private timeLapse As Integer = 5           ' time between images (5 seconds)
Private imageSize As Integer = 600         ' size of current displayed image
Private thumbnailSize As Integer = 200     ' size of "thumbnail" of next image
Private currentImage As Integer = 0        ' index of the current image from imageList

' Get the list of images from the Pictures folder and start the slide show.
Private Async Sub StartSlideShow()
    Dim resultsLibrary =
        Await Windows.Storage.KnownFolders.PicturesLibrary.GetFilesAsync()
    imageList = resultsLibrary
    If (imageList.Count > 0) Then
        Dim image = QueueImage(0, True)
    Else
        MessageBlock.Text = "There are no images in the Pictures library."
    End If
End Sub

' PlayNextImage
' Called when a new image is displayed due to a timeout.
' Removes the current image object and queues a new next image.
' Sets the next image index as the new current image, and increases the size 
' of the new current image. Then sets the timeout to display the next image.

Private Async Sub PlayNextImage(num As Integer)
    ' Stop the timer to avoid repeating.
    If timer IsNot Nothing Then timer.Stop()

    Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        Async Sub()
            SlideShowPanel.Children.Remove(CType(SlideShowPanel.FindName("image" & num), UIElement))
            Dim i = Await QueueImage(num + 2, False)

            currentImage = num + 1
            CType(SlideShowPanel.FindName("image" & currentImage), Image).Width = imageSize
        End Sub)

    timer = New Windows.UI.Xaml.DispatcherTimer()
    timer.Interval = New TimeSpan(0, 0, timeLapse)
    AddHandler timer.Tick, Sub(sender As Object, e As Object)
                               PlayNextImage(num + 1)
                           End Sub
    timer.Start()
End Sub

' QueueImage
' Called to create an image object for the displayed images.

Private Async Function QueueImage(num As Integer, isFirstImage As Boolean) As Task(Of Image)
    ' Create the image element for the specified image index and add to the
    ' slide show div.

    Dim image = New Image()
    image.Width = If(isFirstImage, imageSize, thumbnailSize)
    image.Name = "image" & num
    image.VerticalAlignment = VerticalAlignment.Bottom
    Dim fileContents = Await imageList(num Mod imageList.Count).OpenReadAsync()
    Dim imageBitmap = New BitmapImage()
    imageBitmap.SetSource(fileContents)
    image.Source = imageBitmap

    Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        Sub()
            SlideShowPanel.Children.Add(image)
        End Sub)

    ' If this is the first image of the slide show, queue the next image. Do
    ' not queue if streaming as images are already queued before
    ' streaming using Play To.

    If isFirstImage AndAlso Not streaming Then

        Dim i = Await QueueImage(num + 1, False)

        timer = New Windows.UI.Xaml.DispatcherTimer()
        timer.Interval = New TimeSpan(0, 0, timeLapse)
        AddHandler timer.Tick, Sub(sender As Object, e As Object)
                                   PlayNextImage(num)
                               End Sub
        timer.Start()
    End If

' Use the transferred event of the Play To connection for the current image object
' to "move" to the next image in the slide show. The transferred event occurs
' when the PlayToSource.playNext() method is called, or when the Play To
' Receiver selects the next image.

    AddHandler image.PlayToSource.Connection.Transferred,
        Async Sub(sender As Windows.Media.PlayTo.PlayToConnection,
                  e As Windows.Media.PlayTo.PlayToConnectionTransferredEventArgs)

            currentImage = num + 1

            Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                Sub()
                    CType(SlideShowPanel.FindName("image" & currentImage), Image).Width = imageSize
                End Sub)
        End Sub


    ' Use the statechanged event to determine which action to take or to respond
    ' if the Play To Receiver is disconnected.
    AddHandler image.PlayToSource.Connection.StateChanged,
        Async Sub(sender As Windows.Media.PlayTo.PlayToConnection,
                  e As Windows.Media.PlayTo.PlayToConnectionStateChangedEventArgs)

            Select Case e.CurrentState
                Case Windows.Media.PlayTo.PlayToConnectionState.Disconnected

                    ' If the state is disconnected and the current image index equals the 
                    ' num value passed to queueImage, then the image element is not connected 
                    ' to the Play To Receiver any more. Restart the slide show.
                    ' Otherwise, the current image has been discarded and the slide show
                    ' has moved to the next image. Clear the current image object and
                    ' remove it from the slide show div.

                    If currentImage = num Then
                        Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                            Async Sub()
                                MessageBlock.Text = "Slideshow disconnected"

                                ' Cancel any existing timeout
                                If timer IsNot Nothing Then timer.Stop()

                                ' Clear all image objects from the slide show div
                                SlideShowPanel.Children.Clear()

                                ' Reset the slide show objects and values to their beginning state
                                streaming = False
                                DisconnectButton.Visibility = Visibility.Collapsed
                                InstructionsBlock.Visibility = Visibility.Visible
                                AddHandler DisconnectButton.Click, AddressOf DisconnectButtonClick

                                ' Restart the slide show from the current image index
                                Dim i = Await QueueImage(currentImage, True)
                            End Sub)
                    Else 
                           Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                                Sub()
                                    image.PlayToSource.Next = Nothing

                                    If streaming Then
                                        SlideShowPanel.Children.Remove(image)
                                    End If
                                End Sub)
                    End If

                Case Windows.Media.PlayTo.PlayToConnectionState.Connected

                ' If the state is connected and the previous state is disconnected, 
                ' then the image element is newly connected. Queue up the next image so 
                ' that it is loaded while the current image is being displayed.
                ' If the previous state is rendering, then the user has paused the slideshow 
                ' on the Play To Receiver. Clear the current timeout until the user restarts
                ' the slide show.
                Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                    Async Sub()
                            If e.PreviousState = Windows.Media.PlayTo.PlayToConnectionState.Disconnected Then
                                Dim imageNext = Await QueueImage(num + 1, False)
                                image.PlayToSource.Next = imageNext.PlayToSource
                            ElseIf e.PreviousState = Windows.Media.PlayTo.PlayToConnectionState.Rendering Then
                                If timer IsNot Nothing Then timer.Stop()
                            End If

                            If currentImage = num Then
                                MessageBlock.Text = "Slideshow connected"

                            End If
                        End Sub)

                Case Windows.Media.PlayTo.PlayToConnectionState.Rendering

                ' If the state is rendering and the previous state is
                ' connected, then the Play To Receiver has restarted
                ' the slide show.
                Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
                   Sub()
                           If e.PreviousState = Windows.Media.PlayTo.PlayToConnectionState.Connected Then

                               ' Clear any existing timeout.
                               If timer IsNot Nothing Then timer.Stop()

                               ' Restart the slide show.
                               timer = New Windows.UI.Xaml.DispatcherTimer()
                               timer.Interval = New TimeSpan(0, 0, timeLapse)
                               AddHandler timer.Tick, Sub(s As Object, args As Object)
                                                          image.PlayToSource.PlayNext()
                                                      End Sub
                               timer.Start()
                           End If

                           If currentImage = num Then
                               MessageBlock.Text = "Slideshow rendering"
                           End If
                       End Sub)
            End Select
            End Function

    Return image
End Function

// Set up the Play To contract.

// Used to pass an image to Play To that will not be removed/destroyed
// by the slide show logic. For example, if the user opens the Devices
// charm and the sourcerequested event fires, but the image display timeout
// completes before the user selects a target device, then the image that
// was being displayed is removed and destroyed. initialImage is never 
// destroyed so Play To will always have a valid source to stream.
Image initialImage = null;

private async void SourceRequested(Windows.Media.PlayTo.PlayToManager sender, 
                             Windows.Media.PlayTo.PlayToSourceRequestedEventArgs e)
{
    var deferral = e.SourceRequest.GetDeferral();

    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
    () =>
    {
        initialImage = new Image();

        // Use the statechanged event of the image passed to Play To to determine when
        // the image is finally connected to the Play To Receiver.
        initialImage.PlayToSource.Connection.StateChanged += InitialImageConnectionStateChanged;

        // Provide Play To with the first image to stream.
        e.SourceRequest.SetSource(initialImage.PlayToSource);

        deferral.Complete();
    });
}

private async void InitialImageConnectionStateChanged(Windows.Media.PlayTo.PlayToConnection sender,
                                                      Windows.Media.PlayTo.PlayToConnectionStateChangedEventArgs e)
{
        if (e.CurrentState == Windows.Media.PlayTo.PlayToConnectionState.Connected) {

            await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, 
                async () =>
                {
                    // Clear any existing timeout.
                    if (timer != null) { timer.Stop(); }

                    // Clear the slide show panel.
                    SlideShowPanel.Children.Clear();

                    // Set the slide show objects and values to show that we are streaming.
                    streaming = true;
                    DisconnectButton.Visibility = Visibility.Visible;
                    InstructionsBlock.Visibility = Visibility.Collapsed;

                    // Queue and display the next image.
                    var image = await QueueImage(currentImage, true);
                    initialImage.PlayToSource.Next = image.PlayToSource;
                    initialImage.PlayToSource.PlayNext();
                });
        };
}

// Update the once the user has selected a device to stream to.

private async void SourceSelected(Windows.Media.PlayTo.PlayToManager sender, 
                            Windows.Media.PlayTo.PlayToSourceSelectedEventArgs e)
{
    await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        () =>
        {
            DisconnectButton.Click += DisconnectButtonClick;
            MessageBlock.Text = "Streaming to " + e.FriendlyName + "...";
            DeviceBlock.Text = e.FriendlyName + ".\nClick here to disconnect.";
            var imageBitmap = new Windows.UI.Xaml.Media.Imaging.BitmapImage();
            imageBitmap.SetSource(e.Icon);
            IconImage.Source = imageBitmap;
        });
}

private void DisconnectButtonClick(object sender, RoutedEventArgs e)
{
    Windows.Media.PlayTo.PlayToManager.ShowPlayToUI();
}

' Set up the Play To contract.

' Used to pass an image to Play To that will not be removed/destroyed
' by the slide show logic. For example, if the user opens the Devices
' charm and the sourcerequested event fires, but the image display timeout
' completes before the user selects a target device, then the image that
' was being displayed is removed and destroyed. initialImage is never 
' destroyed so Play To will always have a valid source to stream.
Private initialImage As Image = Nothing

Private Async Sub SourceRequested(sender As Windows.Media.PlayTo.PlayToManager,
                             e As Windows.Media.PlayTo.PlayToSourceRequestedEventArgs)

    Dim deferral = e.SourceRequest.GetDeferral()

    Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
    Sub()
        initialImage = New Image()

        ' Use the statechanged event of the image passed to Play To to determine when
        ' the image is finally connected to the Play To Receiver.
        AddHandler initialImage.PlayToSource.Connection.StateChanged, AddressOf InitialImageConnectionStateChanged

        ' Provide Play To with the first image to stream.
        e.SourceRequest.SetSource(initialImage.PlayToSource)

        deferral.Complete()
    End Sub)
End Sub

Private Async Sub InitialImageConnectionStateChanged(sender As Windows.Media.PlayTo.PlayToConnection,
                                                         e As Windows.Media.PlayTo.PlayToConnectionStateChangedEventArgs)

    If e.CurrentState = Windows.Media.PlayTo.PlayToConnectionState.Connected Then

        Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
            Async Sub()
                ' Clear any existing timeout.
                If timer IsNot Nothing Then timer.Stop()

                ' Clear the slide show panel.
                SlideShowPanel.Children.Clear()

                ' Set the slide show objects and values to show that we are streaming.
                streaming = True
                DisconnectButton.Visibility = Visibility.Visible
                InstructionsBlock.Visibility = Visibility.Collapsed

                ' Queue and display the next image.
                Dim image = Await QueueImage(currentImage, True)
                initialImage.PlayToSource.Next = image.PlayToSource
                initialImage.PlayToSource.PlayNext()
            End Sub)
    End If
End Sub

' Update the once the user has selected a device to stream to.

Private Async Sub SourceSelected(sender As Windows.Media.PlayTo.PlayToManager,
                                 e As Windows.Media.PlayTo.PlayToSourceSelectedEventArgs)

    Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        Sub()
            AddHandler DisconnectButton.Click, AddressOf DisconnectButtonClick
            MessageBlock.Text = "Streaming to " & e.FriendlyName & "..."
            DeviceBlock.Text = e.FriendlyName & "." & vbCr & "Click here to disconnect."
            Dim imageBitmap = New Windows.UI.Xaml.Media.Imaging.BitmapImage()
            imageBitmap.SetSource(e.Icon)
            IconImage.Source = imageBitmap
        End Sub)
End Sub

Private Sub DisconnectButtonClick()
    Windows.Media.PlayTo.PlayToManager.ShowPlayToUI()
End Sub

注解

有关使用 PlayToSource 类的示例，请参阅 媒体转换。

属性

Connection	获取与“播放到”目标的连接。
Next	获取或设置下一个“播放到”源元素。
PreferredSourceUri	指定媒体流的首选统一资源标识符 (URI) ，例如基于云的媒体服务器，用于按引用播放到。

方法

PlayNext()

将下一个“播放到”源元素连接到“播放到”目标。

另请参阅

• 播放到示例
• PlayToReceiver 示例
• 媒体服务器示例