按键发射的原理

onMouseMove   =   function()   {
            arrowAngle(myArrow,   _xmouse,   _ymouse);//角度
};
onMouseDown=function(){
            addBall();//发射
}
myHelp.icon="help"
v   =   100;
startX   =   myArrow._x;
startY   =   myArrow._y;
myArrowNose   =   myArrow._width*.75;
function   addBall()   {
            ++v;
            name   =   "ball"+v;
            var   angle   =   myArrow._rotation;
            var   cosA   =   Math.cos(angle*Math.PI/180);
            var   sinA   =   Math.sin(angle*Math.PI/180);
            var   x   =   startX+myArrowNose*cosA;
            var   y   =   startY+myArrowNose*sinA;
            var   xVel   =   speed*cosA;
            var   yVel   =   speed*sinA;
            duplicateMovieClip(ball,   name,   v);
            this[name]._x   =   x;
            this[name]._y   =   y;
            this[name]._rotation   =   myArrow._rotation;
            this[name].xVelocity   =   xVel;
            this[name].yVelocity   =   yVel;
}
function   arrowAngle(obj,   x,   y)   {
            m   =   eval(obj);
            var   x1   =   x-m._x;
            var   y1   =   y-m._y;
            angle   =   Math.atan2(y1,   x1)*180/math.PI;
            m._rotation   =   angle;
}

myW.setSize(110,150)
myW.contentPath="control"//从库中调用
myW._visible=0
hideCW.clickHandler=function(evt){

            myW._visible   =   evt.target.selected;//控制window组件
}

onClipEvent   (enterFrame)   {
            _parent.speed   =   _parent.myW.content.myNumber.value;
            _parent.myW.content.input=Math.round(_parent.myArrow._rotation*100)/100
            _parent.myW.content.inputx=_parent._xmouse
            _parent.myW.content.inputy=_parent._ymouse
            if   (_name   !=   "ball"   {
                        _x   +=   xVelocity;
                        _y   +=   yVelocity;
            }
}