c# - 如何在 TPL 中停止播放并返回正确的值？

Question

在我的 TPL 应用程序中，我想通过方法 PlayTTS(string text) 播放文本到语音。

public static CancellationTokenSource cTokenSource = new CancellationTokenSource();
public static CancellationToken cToken = cTokenSource.Token;

然后在消费者方法中。

async Task Consumer()
    {
        try
        {
            var executionDataflowBlockOptions = new ExecutionDataflowBlockOptions
            {
                MaxDegreeOfParallelism = 50,
                CancellationToken = cToken
            };
            var consumerBlock = new ActionBlock<AppointmentReminder>(
            remainder =>
            {
               if (cToken.IsCancellationRequested)
                  return;
                Dictionary<string, string> dict = new OutboundDial(ts).RunScript(remainder, cToken);
                // update UI by the returned dictionary
            },
            executionDataflowBlockOptions);

            m_bufferBlock.LinkTo(
            consumerBlock, new DataflowLinkOptions { PropagateCompletion = true });
            await consumerBlock.Completion;
        }

我有一个按钮事件来取消进程(WPF)。

private void Cancel_Click(object sender, RoutedEventArgs e)
{
    cTokenSource.Cancel();
}

您看到 ActionBlock 中有 cToken.IsCancellationRequested，但是它并没有帮助停止方法 OutboundDial(ts).RunScript(剩余部分，cToken); 虽然我传入了取消 token 。

现在让我们看看RunScript方法。

public Dictionary<string, string> RunScript(AppointmentReminder callData, CancellationToken cToken)
    {
        try
        {
             m_ChannelResource = m_TelephonyServer.GetChannel() as SipChannel;
             m_VoiceResource = m_ChannelResource.VoiceResource;
             // Many logging
             // Dial out

            MakeTest(callData, cToken);
        }
        catch
         {throw;}
        finally
        {
            // destroy m_ChannelResource and m_VoiceResource
         }
        return dict;
    }

关键点是方法MakeTest，里面有PlayTTS；

public void MakeTest(AppointmentReminder callData, CancellationToken cToken)
{
    try
    {
        if (!cToken.IsCancellationRequested)
        {
            m_VoiceResource.PlayTTS(callData.Text);  
        }
        else
        {
            cToken.ThrowIfCancellationRequested();
            m_VoiceResource.Stop(); // Stops any current activity on m_VoiceResource.
            dict["ConnectedTime"] = " no connection";
            dict["DialingResult"] = " cancellation";
        }

当我单击取消按钮时，我当前的代码未到达 m_VoiceResource.Stop() 部分。所以我的问题是当cTokenSource.Cancel();时，如何让代码运行在:

m_VoiceResource.Stop(); // Stops any current activity on m_VoiceResource.
dict["ConnectedTime"] = " no connection";
dict["DialingResult"] = " cancellation";

编辑:2014 年 10 月 31 日下午 1:10

根据Servy的评论，我使用了cToken.Register(() => m_VoiceResource.Stop());

我在 OneDrive 创建了一个类似的演示。

Answer 1

在检查 token 是否已取消并开始播放后，您将取消 token 。你永远不会回去并再次执行该条件来停止。

您需要做的只是注册一个回调来取消 token 以停止玩家:

cToken.Register(() => m_VoiceResource.Stop());

只需在开始玩游戏后立即添加该注册即可。