package {
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.ui.MouseCursor;
    import flash.ui.Mouse;
     
    public class 对象投掷 extends Sprite {
         
        private var ball:Ball;
        private var vx:Number;
        private var vy:Number;
        private var bounce:Number=-0.8;
        private var gravity:Number=0.75;
        private var frictionX:Number = 0.98;
        private var frictionY:Number = 0.99;
        private var oldX:Number;
        private var oldY:Number;
         
        //public function Throwing() {
        public function 对象投掷() {
            init();
        }
         
        private function init():void {
            stage.scaleMode=StageScaleMode.NO_SCALE;
            stage.align=StageAlign.TOP_LEFT;
            ball = new Ball(30);
            ball.x = stage.stageWidth/2;
            ball.y = stage.stageHeight/2;
            vx = Math.random()*10-5;
            vy = -10;
            addChild(ball);
            ball.addEventListener(MouseEvent.MOUSE_DOWN, MouseDownHandler);
            ball.addEventListener(MouseEvent.MOUSE_OVER,function(){Mouse.cursor = MouseCursor.HAND;});
            ball.addEventListener(MouseEvent.MOUSE_OUT,function(){Mouse.cursor = MouseCursor.AUTO;});
            addEventListener(Event.ENTER_FRAME, EnterFrameHandler);
        }
         
        private function MouseDownHandler(event:MouseEvent):void {
            oldX = ball.x;
            oldY = ball.y;
            stage.addEventListener(MouseEvent.MOUSE_UP, MouseUpHandler);
            ball.startDrag();
            removeEventListener(Event.ENTER_FRAME, EnterFrameHandler);
            addEventListener(Event.ENTER_FRAME, TrackVelocity);
        }
         
        private function EnterFrameHandler(event:Event):void {
            vy += gravity;
            vx *= frictionX;
            vy *= frictionY;
            ball.x += vx;
            ball.y += vy;
            var left:Number=0;
            var right:Number=stage.stageWidth;
            var top:Number=0;
            var bottom:Number=stage.stageHeight;
            if (ball.x+ball.radius>right) {
                ball.x=right-ball.radius;
                vx*=bounce;
            } else if (ball.x - ball.radius < left) {
                 
                ball.x=left+ball.radius;
                vx*=bounce;
            }
            if (ball.y+ball.radius>bottom) {
                ball.y=bottom-ball.radius;
                vy*=bounce;
            } else if (ball.y - ball.radius < top) {
                ball.y=top+ball.radius;
                vy*=bounce;
            }
        }
         
        //跟踪每一帧小球的速度(坐标位置)
        private function TrackVelocity(event:Event):void {
            vx = ball.x-oldX;
            vy = ball.y-oldY;
            oldX = ball.x;
            oldY = ball.y;
        }
         
        private function MouseUpHandler(e:MouseEvent):void {
            stage.removeEventListener(MouseEvent.MOUSE_UP, MouseUpHandler);
            ball.stopDrag();
            removeEventListener(Event.ENTER_FRAME, TrackVelocity);
            addEventListener(Event.ENTER_FRAME, EnterFrameHandler);
        }
         
         
    }
}