package {
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.utils.getTimer;
    import flash.display.DisplayObject;
    import flash.events.MouseEvent;
    import flash.text.TextField;
 
    public class GridCollision2 extends Sprite {
        private const GRID_SIZE:Number=20;
        private const RADIUS:Number=10;
        private var _balls:Vector.<DisplayObject>;//这里用Vector代替了Array
        private var _grid:CollisionGrid;
        private var _numBalls:int=50;
        private var _text:TextField;
 
        public function GridCollision2() {
            stage.align=StageAlign.TOP_LEFT;
            stage.scaleMode=StageScaleMode.NO_SCALE;
            _text = new TextField();
            _text.background = true;
            _text.backgroundColor = 0xffff99;
            _text.width = 135;
            _text.height = 20;
            _text.alpha = 0.9;
             
             
            _grid=new CollisionGrid(stage.stageWidth,stage.stageHeight,GRID_SIZE);
            _grid.drawGrid(graphics);
 
            makeBalls();
            addChild(_text);
            test();
 
            stage.addEventListener(MouseEvent.CLICK,stageClick);
        }
 
        private function stageClick(e:MouseEvent):void {
            test(true);
        }
 
        private function test(isRestart:Boolean=false):void {
            if (isRestart) {
                for (var i:int=0; i<_numBalls; i++) {
                    var ball:Ball=_balls[i] as Ball;
                    ball.x=Math.random()*stage.stageWidth;
                    ball.y=Math.random()*stage.stageHeight;
                    ball.color = 0xffffff;
                }
            }
 
            var startTime:int;
            var elapsed:int;
            startTime=getTimer();
            for (i=0; i<10; i++) {
                _grid.assign(_balls);//将所有需要检测的ball放入_grid.checks
                var numChecks:int=_grid.checks.length;
                for (var j:int=0; j<numChecks; j+=2) {
                    checkCollision(_grid.checks[j] as Ball,_grid.checks[j+1] as Ball);
                }
            }
            elapsed=getTimer()-startTime;
            trace("Elapsed:",elapsed);
            _text.text = _numBalls + "个小球碰撞检测：" + elapsed.toString();
        }
         
        //初始化小球实例
        private function makeBalls():void {
            _balls=new Vector.<DisplayObject>(_numBalls);
            for (var i:int=0; i<_numBalls; i++) {
                var ball:Ball=new Ball(RADIUS);
                ball.x=Math.random()*stage.stageWidth;
                ball.y=Math.random()*stage.stageHeight;
                ball.alpha = 0.8;
                addChild(ball);
                _balls[i]=ball;
            }
        }
 
        //检测碰撞
        private function checkCollision(ballA:Ball,ballB:Ball):void {
            var dx:Number=ballB.x-ballA.x;
            var dy:Number=ballB.y-ballA.y;
            var dist:Number=Math.sqrt(dx*dx+dy*dy);
            if (dist<ballA.radius+ballB.radius) {
                //(碰撞后的小球变红色)
                ballA.color=0xff0000;
                ballB.color=0xff0000;
            }
        }
    }
}