Unity中Task的实现（主线程中的任务式编程）

发表于2017-06-26

以前介绍了如何把Task移植到Unity中使用，毕竟Unity不支持4.x，貌似也没打算支持。但那个Task里面的东西全是在后台线程执行的。虽然可以用类似invoke的方式（这个我有单独的封装，曾经在官网介绍过），切入到主线程进行操作，但是如果遇到我的任务就是个协程，就歇菜了。因为他可不没办法支持协程当任务。于是我就又花了两天时间捣鼓，写了个UTask的模型。这种模型，有好多人已经封装过，但大家出发点各不相同，我是纯粹的希望任务式编程。

先来看结果吧：

public class Test : MonoBehaviour
{
 
    // Use this for initialization
    void Start()
    {
        var task1 = Dpjia.UnityTask.UTask.Run<int>(() => AA()).ContinueWith<int>(t => BB(t));
    }
 
    IEnumerator AA()
    {
        int res = 100;
        Debug.Log("AA:   "  + res  + "  "+ Time.time);
        yield return new WaitForSeconds(2);
        res += 50;
        Debug.Log("AA:   " + res + "  " + Time.time);
        yield return res;
    }
 
    IEnumerator BB(UTask<int> p_task)
    {
        int res = p_task.Result;
        yield return new WaitForSeconds(1);
        Debug.Log("BB:   " + res + "  " + Time.time);
        yield return new WaitForSeconds(1);
        res *= 2;
        Debug.Log("BB:   " + res + "  " + Time.time);
        yield return null;
    }
}

使用这种方案，我们可以拆分我们的业务为一个个独立的任务，然后顺序去执行就行了。

顺着之前的那两篇文章，一篇是Task，一篇是协程。这里的思路和之前的Task模式是一致的，唯一的区别就是毕竟这里是unity的主线程，不能直接一个action作为任务，那样会卡死主线程的，所以用了协程来作为任务的单位。顺其自然，任务执行中无选择余地的用了MonoBehaviour中的StartCoroutine和StopCoroutine来启动与取消任务。

/// 
/// Dispatches an asynchronous message to coroutine.
/// 
/// 
public Coroutine Post(IEnumerator p_action, Action<object> p_completeCallback)
{
    return g_defaultContext.StartCoroutine(Excute(p_action, p_completeCallback));
}
 
public void Stop(Coroutine p_coroutine)
{
    StopCoroutine(p_coroutine);
}

但这里有所不同的是我做了一层封装，也就是你看到的Excute这个方法

private static IEnumerator Excute(IEnumerator p_coroutine, Action<object> p_completeCallback)
{
    while (p_coroutine.MoveNext())
    {
        yield return p_coroutine.Current;
    }
    if (p_completeCallback != null)
    {
        p_completeCallback(p_coroutine.Current);
    }
}

这么写看起来很诡异吧，因为这样写我可以拿到最后一个yield return的值作为一个协程的返回值。（记住协程本身是没有返回值的，他实际上是个类，他的主体就是movenext，这个在前一篇有过讲解，当然也就不可以使用ref，out来输出了。我也是想了各种办法，最后测试，发现可以用yield return来实现的。）
其实只要你熟悉了之前的Task的机制，再熟悉了这里对任务原型的选择以及任务的启动结束的使用，你也就可以实现了。因为是链式编程，所以有两行代码对你比较有价值，如果你想实现一个和我一样的东西的话。

1	`protected` `List m_continuationActions =` `new` `List();` `protected` `List m_continuationTasks =` `new` `List();`

m_continuationActions存的是任务结束后的action，这个action就是彻底结束了，不会再返回个任务让你继续链路下去。
下一个存在的就是后续的任务，一个任务可以有多个后续任务，虽然一般情形我们是A->b->c->d。但也有很多A结束后同时运行b和c两个或若干个任务。
当然有扇出，肯定有扇入。所以有WhenAll和WhenAny

/// 
/// Creates a task that is complete when all of the provided tasks are complete.
/// If any of the tasks has an exception, all exceptions raised in the tasks will
/// be aggregated into the returned task. Otherwise, if any of the tasks is cancelled,
/// the returned task will be cancelled.
/// 
/// The tasks to aggregate.
/// A task that is complete when all of the provided tasks are complete.
public static UTask WhenAll(IEnumerable p_tasks)
{
    var taskArr = p_tasks.ToArray();
    if (taskArr.Length == 0)
    {
        return UTask.FromResult(0);
    }
    var tcs = new UTaskCompletionSource<object>();
    UTask.Factory.ContinueWhenAll(taskArr, _ =>
    {
        var exceptions = taskArr.Where(p => p.IsFaulted).Select(p => p.Exception).ToArray();
        if (exceptions.Length > 0)
        {
            tcs.SetException(new System.Threading.Tasks.AggregateException(exceptions));
        }
        else if (taskArr.Any(t => t.IsCanceled))
        {
            tcs.SetCanceled();
        }
        else
        {
            tcs.SetResult(0);
        }
    });
    return tcs.Task;
}

/// 
/// Waits for any of the provided Task objects to complete execution.
/// 
/// 
/// 
internal static UTask WhenAny(IEnumerable p_tasks)
{
    var tcs = new UTaskCompletionSource();
    foreach (var task in p_tasks)
    {
        task.ContinueWith(t => tcs.TrySetResult(t));
    }
    return tcs.Task;
}

另外可能需要补充下的就是，启动任务的方法原型为

[C#] 纯文本查看复制代码

/// 
/// Creates and starts a Task
/// 
/// 
/// 
/// 
public UTask StartNew(Func p_func)

至此，如果你愿意，花费一两天时间，你也能实现你的版本。欢迎交流。

上面的是MainThread的Task，前面的那篇是Backgroud的Task。但是我们正常使用中很多场景是需要前台切后台，后台处理完了切入前台。以前我们都是通过各种锁信号来实现异步与同步的概念。如果使用Task的概念，则只要针对foregroud的task提供切入后台task的方法，backgroud的task提供切入前台的方法即可。

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/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Func p_continuation)
{
    return p_task.ContinueToBackground(p_continuation, CancellationToken.None);
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Func p_continuation, CancellationToken p_cancellationToken)
{
    TaskCompletionSource tcs = new TaskCompletionSource();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    p_task.ContinueWith(t =>
    {
        TaskScheduler.FromCurrentSynchronizationContext().Post(() =>
        {
            try
            {
                tcs.SetResult(p_continuation());
                cancellation.Dispose();
            }
            catch (Exception e)
            {
                tcs.SetException(e);
                cancellation.Dispose();
            }
        });
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Func p_continuation)
{
    return p_task.ContinueToBackground(p_continuation, CancellationToken.None);
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Func p_continuation, CancellationToken p_cancellationToken)
{
    TaskCompletionSource tcs = new TaskCompletionSource();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    p_task.ContinueWith(t =>
    {
        TaskScheduler.FromCurrentSynchronizationContext().Post(() =>
        {
            try
            {
                tcs.SetResult(p_continuation(t));
                cancellation.Dispose();
            }
            catch (Exception e)
            {
                tcs.SetException(e);
                cancellation.Dispose();
            }
        });
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Action p_continuation, CancellationToken p_cancellationToken)
{
    TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    p_task.ContinueWith(t =>
    {
        TaskScheduler.FromCurrentSynchronizationContext().Post(() =>
        {
            try
            {
                p_continuation();
                tcs.SetResult(null);
                cancellation.Dispose();
            }
            catch (Exception e)
            {
                tcs.SetException(e);
                cancellation.Dispose();
            }
        });
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Action p_continuation)
{
    return p_task.ContinueToBackground(p_continuation, CancellationToken.None);
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Action p_continuation, CancellationToken p_cancellationToken)
{
    TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    p_task.ContinueWith(t =>
    {
        TaskScheduler.FromCurrentSynchronizationContext().Post(() =>
        {
            try
            {
                p_continuation(t);
                tcs.SetResult(null);
                cancellation.Dispose();
            }
            catch (Exception e)
            {
                tcs.SetException(e);
                cancellation.Dispose();
            }
        });
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static Task ContinueToBackground(this UTask p_task, Action p_continuation)
{
    return p_task.ContinueToBackground(p_continuation, CancellationToken.None);
}
 
/// 
/// switch to backgroud processor, ForegroundInvoker
/// 
/// 
/// 
/// 
/// 
public static void ContinueToForeground(this Task p_task, Action p_continuation)
{
    p_task.ContinueWith(t =>
    {
        Dpjia.Processor.ForegroundInvoker.Invoke(() =>
        {
            p_continuation();
        });
    });
}
 
/// 
/// switch to backgroud processor, ForegroundInvoker
/// 
/// 
/// 
/// 
/// 
public static void ContinueToForeground(this Task p_task, Action p_continuation)
{
    p_task.ContinueWith(t =>
    {
        Dpjia.Processor.ForegroundInvoker.Invoke(() =>
        {
            p_continuation(t);
        });
    });
}
 
/// 
/// switch to backgroud processor, ForegroundInvoker
/// 
/// 
/// 
/// 
/// 
public static UTask ContinueToForeground(this Task p_task, Func p_continuation, CancellationToken p_cancellationToken)
{
    UTaskCompletionSource tcs = new UTaskCompletionSource();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    tcs.Task.TaskGenerator = p_continuation;
    tcs.Task.ReturnResult = p =>
    {
        try
        {
            tcs.SetResult((TResult)p);
            cancellation.Dispose();
        }
        catch (Exception e)
        {
            tcs.SetException(e);
            cancellation.Dispose();
        }
    };
    p_task.ContinueWith(t =>
    {
        Dpjia.Processor.ForegroundInvoker.Invoke(() =>
        {
            UTaskScheduler.FromCurrentSynchronizationContext().Post(tcs.Task.TaskGenerator(), tcs.Task.ReturnResult);
        });
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, thread pool
/// 
/// 
/// 
/// 
/// 
public static UTask ContinueToForeground(this Task p_task, Func p_continuation)
{
    return p_task.ContinueToForeground(p_continuation, CancellationToken.None);
}
 
/// 
/// switch to backgroud processor, ForegroundInvoker
/// 
/// 
/// 
/// 
/// 
public static UTask ContinueToForeground(this Task p_task, Func p_continuation, CancellationToken p_cancellationToken)
{
    UTaskCompletionSource tcs = new UTaskCompletionSource();
    var cancellation = p_cancellationToken.Register(() => tcs.TrySetCanceled());
    tcs.Task.TaskGenerator = () => p_continuation(p_task);
    tcs.Task.ReturnResult = p =>
    {
        try
        {
            tcs.SetResult((TResult)p);
            cancellation.Dispose();
        }
        catch (Exception e)
        {
            tcs.SetException(e);
            cancellation.Dispose();
        }
    };
 
    p_task.ContinueWith(t =>
    {
        Dpjia.Processor.ForegroundInvoker.Invoke(() =>
        {
            UTaskScheduler.FromCurrentSynchronizationContext().Post(tcs.Task.TaskGenerator(), tcs.Task.ReturnResult);
        });
 
    });
    return tcs.Task;
}
 
/// 
/// switch to backgroud processor, ForegroundInvoker
/// 
/// 
/// 
/// 
/// 
public static UTask ContinueToForeground(this Task p_task, Func p_continuation)
{
    return p_task.ContinueToForeground(p_continuation, CancellationToken.None);
}

然后就可以方便的前台后台切换

[AppleScript] 纯文本查看复制代码

// Use this for initialization
void Start()
{
    Dpjia.Processor.ForegroundInvoker.Initialize();
    Debug.Log(Thread.CurrentThread.ManagedThreadId);
    UTask.Run<int>(() => AA()).ContinueWith<int>(t => BB(t)).ContinueToBackground(()=>
    {
        Debug.Log(Thread.CurrentThread.ManagedThreadId);
    }).ContinueToForeground(()=> { Debug.Log(Thread.CurrentThread.ManagedThreadId); });
}
 
IEnumerator AA()
{
    int res = 100;
    Debug.Log("AA:   "  + res  + "  "+ Time.time);
    yield return new WaitForSeconds(2);
    res += 50;
    Debug.Log("AA:   " + res + "  " + Time.time);
    yield return res;
}
 
IEnumerator BB(UTask<int> p_task)
{
    int res = p_task.Result;
    yield return new WaitForSeconds(1);
    Debug.Log("BB:   " + res + "  " + Time.time);
    yield return new WaitForSeconds(1);
    res *= 2;
    Debug.Log("BB:   " + res + "  " + Time.time);
    yield return null;
}

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Unity中Task的实现（主线程中的任务式编程）