Windows IoT Raspberry Pi 3 c# 在不同页面中播放音频

Question

我正在 Rasp Pi 3 上制作一个应用程序，我可以在其中触发“播放页面”上的一个按钮，以在页面中使用 MediaPlayer 激活音频播放。一旦我切换到另一个页面，音频将继续在后台播放，但是一旦我导航回“播放页面”，音频仍在播放，但由于我的 mediaPlayer = new MediaPlayer(); 我失去了对 MediaPlayer 的控制；线。如果它处于重复模式，我将无法停止播放并且如果我触发另一条消息，则新消息和现有消息将同时播放。

即使在页面之间切换时，如何确保一次只播放一个 MediaPlayer。 请帮忙。谢谢。

修改后的代码：

public sealed partial class MessagePage : Page
{

   private object syncObj = new object();

   public MessagePage()
       {
           this.InitializeComponent();
           startclock();

           this.Home.Click += Home_Click;
           this.Message.Click += Message_Click;

           //mediaPlayer = new MediaPlayer();
           mediaPlayer = this.GetInstance();

           //mediaPlayer.MediaEnded += MediaPlayer_MediaEnded;
           //mediaPlayer.MediaOpened += MediaPlayer_MediaOpened;
       }

    public MediaPlayer GetInstance()
       {
           lock (syncObj)
           {
               if (mediaPlayer == null)
               {
                   mediaPlayer = new MediaPlayer();
                   mediaPlayer.MediaEnded += MediaPlayer_MediaEnded;
                   mediaPlayer.MediaOpened += MediaPlayer_MediaOpened;
               }
           }

           return mediaPlayer;
       }
   }

旧代码：

public MessagePage()
    {
        this.InitializeComponent();
        startclock();

        this.Home.Click += Home_Click;
        this.Message.Click += Message_Click;

        mediaPlayer = new MediaPlayer();
        mediaPlayer.MediaEnded += MediaPlayer_MediaEnded;

    }

private async void Btn_Click(object sender, RoutedEventArgs e)
    {
        StorageFolder externalDevices = KnownFolders.RemovableDevices;
        IReadOnlyList<StorageFolder> externalDrives = await externalDevices.GetFoldersAsync();
        StorageFolder usbStorage = externalDrives[0];

        if (usbStorage != null)
        {
            StorageFolder storageFolder = KnownFolders.RemovableDevices;
            StorageFile audioFile = await usbStorage.GetFileAsync("message1.mp3");
            mediaPlayer.Source = Windows.Media.Core.MediaSource.CreateFromStorageFile(audioFile);
            mediaPlayer.Play();
            TextBlock.Text = "Playing Message 1...";
        }
        else
        {
            TextBlock.Text = "No USB Storage Detected...";
        };
    }

Answer 1

您需要在这里使用singleton pattern。单例模式是一种软件设计模式，它将类的实例化限制为一个对象。当需要一个对象来协调整个系统的动作时，这很有用。

    private static readonly object syncObj = new object(); 

    public MediaPlayer GetInstance()
    {
        lock (syncObj)
        {
            if (mediaPlayer == null)
            {
                mediaPlayer = new MediaPlayer();
                mediaPlayer.MediaEnded += MediaPlayer_MediaEnded;
            }
        }

        return mediaPlayer;
    }

    public MessagePage()
    {
        this.InitializeComponent();
        startclock();

        this.Home.Click += Home_Click;
        this.Message.Click += Message_Click;

        //mediaPlayer = new MediaPlayer();
        mediaPlayer = this.GetInstance();

    }