如何在actionscript中的回调函数中使用类的方法？

Question

在回调函数中调用类的方法时,不能使用thisobject.
要调用该方法,在JavaScript中,我声明that的变量,分配this到that,并且使用that回调内部调用的方法this.

在动作脚本中,我是否必须像在javascript中那样做？

以下代码是that用于在回调内调用方法的示例.
动作中有更简单的方法吗？

class C {
    private var that:C;

    function C() {
        that = this
    }

    public function f1():void {
        var sp:Sprite = new Sprite;

        sp.addEventListener(MouseEvent.CLICK, function():void {
            this.f2(); // this doesn't work
            that.f2(); // that works
        });
    }

    public function f2():void {
        trace('hello');
    }
}

Answer 1

如果将回调函数作为C类的方法,则可以访问this.

 public class C
 {
     private function f1():void
     {
         var sp:Sprite = new Sprite();

         sp.addEventListener(MouseEvent.CLICK, callback);
     }

     private function callback(event:MouseEvent):void
     {
         this.f2();
     }

     private function f2():void
     {
         trace("Hello World");
     }
}

现在this引用类C的实例,其范围是整个类.

Answer 2

这是另一种方法:

package some.package {
    class SomeSprite extends Sprite {
        public function f1():void
        {
            var sprite1:Sprite = new Sprite;
            sprite1.addEventListener(MouseEvent.CLICK,
                (new Closure(f2, this, ["Hello"], sprite1).handler));

            var sprite2:Sprite = new Sprite;
            sprite2.addEventListener(MouseEvent.CLICK,
                (new Closure(f2, this, ["Bye Bye"], sprite2).handler));
        }

        private function f2(message:String):void
        {
            trace(message);
        }
    }
}

class Closure {
    public var callback:Function;
    public var thisObj:Object;
    public var params:Array;
    public var dispatcher:IEventDispatcher;
    public var cleanAfterCallback:Boolean = true;

    function Closure(callback:Function, thisObj:Object, 
        params:Array, dispatcher:IEventDispatcher)
    {
        this.callback = callback;
        this.thisObj = thisObj;
        this.params = params;
        this.dispatcher = dispatcher;
    }

    public function handler(e:Event):void
    {
        callback.apply(thisObj, params);

        if (cleanAfterCallback)
            dispatcher.removeEventListener(e.type, eventHandler)
    }
}