Question

package 
{
    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.ui.Keyboard;
    import flash.events.KeyboardEvent;
    import flash.events.MouseEvent;


    public class supportForce extends MovieClip
    {
        public function supportForce()
        {
            stage.addEventListener(KeyboardEvent.KEY_DOWN, onDown);
            stage.addEventListener(KeyboardEvent.KEY_UP, onUp);
            stage.addEventListener(Event.ENTER_FRAME, keyCheck);
        }
        private function onUp(e:KeyboardEvent):void
        {
            _keyDownStatus[e.keyCode] = false;
        }
        private function onDown(e:KeyboardEvent):void
        {
            _keyDownStatus[e.keyCode] = true;
        }
        private function keyCheck(event:Event)
        {
            if (_keyDownStatus[90])
            {
                var GreenLight:Projectile1 = new Projectile1();
                stage.addChild(GreenLight);
                GreenLight.x = Player2Child.x;
                GreenLight.y = Player2Child.y;
            }
        GreenLight.x -= defaultSpeed;
        }
    }
}

所以这里的抛射物是Projectile1，它在keyCheck函数中被声明为GreenLight。所以在同一个函数（ENTER.FRAME函数）中，GreenLight应该向左移动。这不会发生，也会出现错误，说明TypeError：错误＃1009：无法访问空对象引用的属性或方法。在supportForce / keyCheck（）出现。提前谢谢。

Answer 1

在你的keyCheck函数中，如果_keyDownStatus [90]为假，GreenLight将为null

所以把GreenLight作为一个类变量

    private var lights:Array = [];

    private function keyCheck(event:Event)
    {
        if (_keyDownStatus[90])
        {

             var GreenLight:Projectile1 = new Projectile1();
             stage.addChild(GreenLight);
             GreenLight.x = Player2Child.x;
             GreenLight.y = Player2Child.y;


             for each (var l:Projectile1 in lights)
             {
                 l.x -= defaultSpeed;
             }

              lights.push(GreenLight);
        }
        else
        {
              //remove all Projectile1s in lights from stage and clear lights if you want
        }

    }

Answer 2

你在if条件范围内创建GreenLight，如果keyCode不是90，则Projectile1的对象未创建，GreenLight.x -= defaultSpeed;那里GreenLight为空

弹丸不会像预期的那样移动

2 个答案: