144 lines
5.0 KiB
Markdown
144 lines
5.0 KiB
Markdown
# 单线程异步
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前面几个例子都是多线程实现的异步，但是异步显然不仅仅是多线程的。我们在之前的例子中使用了Sleep来实现时间的等待，每一个计时器都需要使用一个线程，会导致线程切换频繁，这个实现效率很低，平常是不会这样做的。一般游戏逻辑中会设计一个单线程的计时器，我们这里做一个简单的实现，用来讲解单线程异步。
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```csharp
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// example2_3
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class Program
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{
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private static int loopCount = 0;
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private static long time;
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private static Action action;
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static void Main(string[] args)
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{
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Console.WriteLine($"主线程: {Thread.CurrentThread.ManagedThreadId}");
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Crontine();
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while (true)
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{
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Thread.Sleep(1);
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CheckTimerOut();
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++loopCount;
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if (loopCount % 10000 == 0)
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{
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Console.WriteLine($"loop count: {loopCount}");
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}
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}
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}
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private static void Crontine()
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{
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WaitTimeAsync(5000, WaitTimeAsyncCallback1);
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}
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private static void WaitTimeAsyncCallback1()
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{
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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WaitTimeAsync(4000, WaitTimeAsyncCallback2);
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}
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private static void WaitTimeAsyncCallback2()
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{
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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WaitTimeAsync(3000, WaitTimeAsyncCallback3);
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}
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private static void WaitTimeAsyncCallback3()
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{
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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}
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private static void CheckTimerOut()
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{
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if (time == 0)
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{
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return;
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}
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long nowTicks = DateTime.Now.Ticks / 10000;
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if (time > nowTicks)
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{
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return;
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}
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time = 0;
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action.Invoke();
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}
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private static void WaitTimeAsync(int waitTime, Action a)
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{
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time = DateTime.Now.Ticks / 10000 + waitTime;
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action = a;
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}
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}
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```
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这个例子同样实现了一个简单的计时方法，WaitTimeAsync调用时会将回调方法跟时间记录下来，主线程每帧都会调用CheckTimerOut，CheckTimerOut里面判断计时器是否过期，过期了则调用回调方法。整个逻辑都在主线程中完成，同样是异步方法。所以异步并非多线程，单线程同样可以异步。上面的例子同样可以改成await的形式。
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```csharp
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// example2_3_2
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class Program
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{
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private static int loopCount = 0;
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private static long time;
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private static TaskCompletionSource<bool> tcs;
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static void Main(string[] args)
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{
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Console.WriteLine($"主线程: {Thread.CurrentThread.ManagedThreadId}");
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Crontine();
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while (true)
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{
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Thread.Sleep(1);
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CheckTimerOut();
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++loopCount;
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if (loopCount % 10000 == 0)
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{
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Console.WriteLine($"loop count: {loopCount}");
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}
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}
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}
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private static async void Crontine()
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{
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await WaitTimeAsync(5000);
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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await WaitTimeAsync(4000);
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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await WaitTimeAsync(3000);
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Console.WriteLine($"当前线程: {Thread.CurrentThread.ManagedThreadId}, WaitTimeAsync finsih loopCount的值是: {loopCount}");
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}
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private static void CheckTimerOut()
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{
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if (time == 0)
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{
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return;
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}
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long nowTicks = DateTime.Now.Ticks / 10000;
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if (time > nowTicks)
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{
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return;
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}
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time = 0;
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tcs.SetResult(true);
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}
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private static Task WaitTimeAsync(int waitTime)
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{
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TaskCompletionSource<bool> t = new TaskCompletionSource<bool>();
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time = DateTime.Now.Ticks / 10000 + waitTime;
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tcs = t;
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return t.Task;
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}
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}
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```
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上面这个例子所有调用全部在主线程中完成，并且使用了await，因此await并不会开启多线程，await具体用没用多线程完全取决于具体的实现
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