我的儿子正在写一个简单的RPG游戏，其中包含许多非玩家角色（又名NPC）。每个NPC都有一个相关的“脚本”来控制它的行为。我们将使用迷你自定义脚本语言来编写这些行为，但我现在想知道在C＃5 / Async中是否会做得更好。
举一个非常简单的例子，假设其中一个NPC只是在两点之间走，我觉得写这样的东西会很好：
while (true)
{
await WalkTo(100,100);
await WalkTo(200,200);
}
WalkTo方法将是一个异步方法，它处理在两点之间行走的所有操作，并在游戏循环的多个帧中执行此操作。它不是可以卸载到后台线程的阻塞方法。
这就是我被困住的地方......我无法以这种方式找到任何使用async / await的例子，但它似乎对它来说是完美的。
想法？
这是我想要做的一些非常粗略的伪代码：
class NpcBase
{
// Called from game loop
public void onUpdate(double elapsedTime)
{
// Move the NPC
.
.
.
// Arrived at destination?
if (Arrived)
{
// How do I trigger that the task is finished?
_currentTask.MarkComplete();
}
}
// Async method called by NPC "script"
public async Task WalkTo(int x, int y)
{
// Store new target location
// return a task object that will be "triggered" when the walk is finished
_currentTask = <something??>
return _currentTask;
}
Task _currentTask;
}
答案 0 :(得分：4)
好吧，听起来有一种选择是为游戏的每一帧提供TaskCompletionSource。然后，您可以等待WalkTo中的Task，并将结果设置为OnUpdate：
private TaskCompletionSource<double> currentFrameSource;
// Called from game loop
public void OnUpdate(double elapsedTime)
{
...
var previousFrameSource = currentFrameSource;
currentFrameSource = new TaskCompletionSource<double>();
// This will trigger all the continuations...
previousFrameSource.SetResult(elapsedTime);
}
// Async method called by NPC "script"
public async Task WalkTo(int x, int y)
{
// Store new target location
while (/* we're not there yet */)
{
double currentTime = await currentFrameSource.Task;
// Move
}
}
我不确定这会有多高效，不可否认......但它应该有效。
答案 1 :(得分：0)
我想我已经在一个简单的测试程序中找到了它
首先，我有一个像这样的NPC基类：
编辑：更新了NpcBase以使用TaskCompletionSource：
public class NpcBase
{
// Derived classes to call this when starting an async operation
public Task BeginTask()
{
// Task already running?
if (_tcs!= null)
{
throw new InvalidOperationException("busy");
}
_tcs = new TaskCompletionSource<int>();
return _tcs.Task;
}
TaskCompletionSource<int> _tcs;
// Derived class calls this when async operation complete
public void EndTask()
{
if (_tcs != null)
{
var temp = _tcs;
_tcs = null;
temp.SetResult(0);
}
}
// Is this NPC currently busy?
public bool IsBusy
{
get
{
return _tcs != null;
}
}
}
供参考，这是旧版本的NpcBase，带有自定义IAsyncResult实现，而不是TaskCompletionSource：
// DONT USE THIS, OLD VERSION FOR REFERENCE ONLY
public class NpcBase
{
// Derived classes to call this when starting an async operation
public Task BeginTask()
{
// Task already running?
if (_result != null)
{
throw new InvalidOperationException("busy");
}
// Create the async Task
return Task.Factory.FromAsync(
// begin method
(ac, o) =>
{
return _result = new Result(ac, o);
},
// End method
(r) =>
{
},
// State object
null
);
}
// Derived class calls this when async operation complete
public void EndTask()
{
if (_result != null)
{
var temp = _result;
_result = null;
temp.Finish();
}
}
// Is this NPC currently busy?
public bool IsBusy
{
get
{
return _result != null;
}
}
// Result object for the current task
private Result _result;
// Simple AsyncResult class that stores the callback and the state object
class Result : IAsyncResult
{
public Result(AsyncCallback callback, object AsyncState)
{
_callback = callback;
_state = AsyncState;
}
private AsyncCallback _callback;
private object _state;
public object AsyncState
{
get { return _state; ; }
}
public System.Threading.WaitHandle AsyncWaitHandle
{
get { throw new NotImplementedException(); }
}
public bool CompletedSynchronously
{
get { return false; }
}
public bool IsCompleted
{
get { return _finished; }
}
public void Finish()
{
_finished = true;
if (_callback != null)
_callback(this);
}
bool _finished;
}
}
接下来，我有一个简单的“NPC”在一个维度上移动。当moveTo操作开始时，它调用NpcBase中的BeginTask。到达目的地后，它会调用EndTask（）。
public class NpcTest : NpcBase
{
public NpcTest()
{
_position = 0;
_target = 0;
}
// Async operation to count
public Task MoveTo(int newPosition)
{
// Store new target
_target = newPosition;
return BeginTask();
}
public int Position
{
get
{
return _position;
}
}
public void onFrame()
{
if (_position == _target)
{
EndTask();
}
else if (_position < _target)
{
_position++;
}
else
{
_position--;
}
}
private int _position;
private int _target;
}
最后，一个简单的WinForms应用程序来驱动它。它由一个按钮和两个标签组成。单击该按钮将启动NPC，并且它们的位置将显示在标签上。
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void onButtonClick(object sender, EventArgs e)
{
RunNpc1();
RunNpc2();
}
public async void RunNpc1()
{
while (true)
{
await _npc1.MoveTo(20);
await _npc1.MoveTo(10);
}
}
public async void RunNpc2()
{
while (true)
{
await _npc2.MoveTo(80);
await _npc2.MoveTo(70);
}
}
NpcTest _npc1 = new NpcTest();
NpcTest _npc2 = new NpcTest();
private void timer1_Tick(object sender, EventArgs e)
{
_npc1.onFrame();
_npc2.onFrame();
label1.Text = _npc1.Position.ToString();
label2.Text = _npc2.Position.ToString();
}
}
它的工作原理似乎都在主UI线程上运行......这就是我想要的。
当然需要修复它来处理取消操作，异常等......但基本的想法就在那里。