c# - Xamarin Forms 异步播放声音

Question

我可以使用 Xamarin 表单(Android 和 iOS)成功播放声音，但我还需要实现以下目标:

我需要等待，以便如果“播放”多个声音，一个会在下一个之前完成。

我需要返回一个 bool 值来指示操作是否成功。

这是我当前的简化代码(适用于 iOS 平台):

    public Task<bool> PlayAudioTask(string fileName)
    {
        var tcs = new TaskCompletionSource<bool>();

        string filePath = NSBundle.MainBundle.PathForResource(
                Path.GetFileNameWithoutExtension(fileName), Path.GetExtension(fileName));

        var url = NSUrl.FromString(filePath);

        var _player = AVAudioPlayer.FromUrl(url);

        _player.FinishedPlaying += (object sender, AVStatusEventArgs e) =>
            {
                _player = null;
                tcs.SetResult(true);
            };

        _player.Play();

        return tcs.Task;
    }

为了测试该方法，我尝试这样调用它:

    var res1 = await _audioService.PlayAudioTask("file1");
    var res2 = await _audioService.PlayAudioTask("file2");
    var res3 = await _audioService.PlayAudioTask("file3");

我曾希望听到 file1、file2、file3 的音频。但是我只听到文件 1 并且代码似乎没有达到第二个等待。

谢谢

Answer 1

我认为您的问题是 AVAudioPlayer _player在它完成之前被清除。如果您要在 FinsihedPlaying 中添加调试，你会注意到你从来没有达到那个点。

试试这些改变，我做了一个私有(private)的AVAudioPlayer坐在 Task 外面

(我使用以下指南作为引用 https://developer.xamarin.com/recipes/ios/media/sound/avaudioplayer/ )

    public async void play()
    {

        System.Diagnostics.Debug.WriteLine("Play 1");
        await PlayAudioTask("wave2.wav");

        System.Diagnostics.Debug.WriteLine("Play 2");
        await PlayAudioTask("wave2.wav");

        System.Diagnostics.Debug.WriteLine("Play 3");
        await PlayAudioTask("wave2.wav");

    }


    private AVAudioPlayer player;  // Leave the player outside the Task

    public Task<bool> PlayAudioTask(string fileName)
    {
        var tcs = new TaskCompletionSource<bool>();

        // Any existing sound playing?
        if (player != null)
        {
            //Stop and dispose of any sound
            player.Stop();
            player.Dispose();
        }

        string filePath = NSBundle.MainBundle.PathForResource(
                Path.GetFileNameWithoutExtension(fileName), Path.GetExtension(fileName));

        var url = NSUrl.FromString(filePath);

        player = AVAudioPlayer.FromUrl(url);

        player.FinishedPlaying += (object sender, AVStatusEventArgs e) =>
        {
            System.Diagnostics.Debug.WriteLine("DONE PLAYING");
            player = null;
            tcs.SetResult(true);
        };


        player.NumberOfLoops = 0;
        System.Diagnostics.Debug.WriteLine("Start Playing");
        player.Play();

        return tcs.Task;
    }