如何选择并播放列表中的多首歌曲？

Question

我有一个要求，我需要使用 wpf 在窗口上播放多首音频歌曲。任何人都可以建议实现此目的的最佳方法。

我有窗户。我将在列表框中显示歌曲列表。用户应该能够从列表框中选择多首歌曲并单击播放。

我必须一一播放用户选择的所有音频歌曲。

我会感谢你的帮助。

Answer 1

最简单的方法是使用一个 ListBox 控件，并将其 ItemsSource 属性绑定到某个集合（例如“SongList”）。

<ListBox Name="lstSongs" ItemsSource="{Binding Path=SongList}" SelectionMode="Extended" Grid.Row="1" />

在页面上有一个 MediaElement 控件监听下一首歌曲

<MediaElement Name="player" MediaEnded="MediaElement_MediaEnded" LoadedBehavior="Play" UnloadedBehavior="Stop" Source="{Binding Path=CurrentlyPlaying}" />

当用户单击表单上的按钮时，当前选定的项目将添加到队列中。通过读取 ListBox.SelectedItems 属性可以找到当前选定的项目。

private void cmdQueueItems_Click(object sender, RoutedEventArgs e)
{
    Queue = lstSongs.SelectedItems.OfType<Uri>().ToList();
    playNext();
}

然后，您开始播放队列中的第一个项目，当引发 MediaElement.MediaEnded 事件时，将当前正在播放的项目替换为队列中的下一个项目（如果有可用的项目）。

private void MediaElement_MediaEnded(object sender, RoutedEventArgs e)
{
    playNext();
}

您将执行此操作，直到用户点击预定义的停止按钮。

playNext() 方法很简单

private void playNext()
{
    CurrentlyPlaying = Queue.FirstOrDefault();

    if (CurrentlyPlaying != null)
        Queue.Remove(CurrentlyPlaying);
}

（确保 CurrentPlaying 属性引发 INotifyPropertyChanged.PropertyChanged 事件）

MainWindow.xaml.cs

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string name)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(name));
    }

    public List<Uri> Queue { get; private set; }

    #region CurrentlyPlaying Definition

    private Uri _CurrentlyPlaying = null;

    public Uri CurrentlyPlaying
    {
        get
        {
            return _CurrentlyPlaying;
        }
        set
        {
            _CurrentlyPlaying = value;
            OnPropertyChanged("CurrentlyPlaying");
        }
    }

    #endregion // end of CurrentlyPlaying region

    public System.Collections.ObjectModel.ObservableCollection<Uri> SongList { get; private set; }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;

        SongList = new System.Collections.ObjectModel.ObservableCollection<Uri>();

        SongList.Add(new Uri(@"E:\Music\_relaxation\African Drums - Tribal Music.mp3"));
        SongList.Add(new Uri(@"E:\Music\Disturbed\Disturbed - A Welcme Burden.mp3"));
    }

    private void cmdQueueItems_Click(object sender, RoutedEventArgs e)
    {
        Queue = lstSongs.SelectedItems.OfType<Uri>().ToList();
        playNext();
    }

    private void cmdSkipItem_Click(object sender, RoutedEventArgs e)
    {
        playNext();
    }

    private void MediaElement_MediaEnded(object sender, RoutedEventArgs e)
    {
        playNext();
    }

    private void playNext()
    {
        CurrentlyPlaying = Queue.FirstOrDefault();

        if (CurrentlyPlaying != null)
            Queue.Remove(CurrentlyPlaying);
    }
}

<强>MainWindow.xaml

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>

    <MediaElement Name="player" MediaEnded="MediaElement_MediaEnded" LoadedBehavior="Play" UnloadedBehavior="Stop" Source="{Binding Path=CurrentlyPlaying}" />
    <ListBox Name="lstSongs" ItemsSource="{Binding Path=SongList}" SelectionMode="Extended" Grid.Row="1" />
    <Button Content="Play selected" Click="cmdQueueItems_Click" Grid.Row="2" />
    <Button Content="Skip" Click="cmdSkipItem_Click" Grid.Row="3" />
</Grid>