Box2D范例三修版

package
{
	/**
	 * @create_time Apr 13, 2012 4:00:54 PM
	 * @author Ado
	 * @E-mail: adodo08@163.com
	 **/
	import Box2D.Collision.Shapes.b2CircleShape;
	import Box2D.Collision.Shapes.b2PolygonShape;
	import Box2D.Common.Math.b2Vec2;
	import Box2D.Dynamics.b2Body;
	import Box2D.Dynamics.b2BodyDef;
	import Box2D.Dynamics.b2DebugDraw;
	import Box2D.Dynamics.b2FixtureDef;
	import Box2D.Dynamics.b2World;
	
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;

	[SWF(width=1000,height=600,frameRate=24,backgroundColor=0xcccccc)]
	public class BoxTester extends Sprite
	{
		private var world:b2World;
		private var worldSprite:Sprite;
		private var drawScale:Number=20;
		public function BoxTester()
		{
			//创建世界，两个参数：重力与是否睡眠
			world = new b2World(new b2Vec2(0,0),true);
			//地板
			createFloor(0,(stage.stageHeight - 10)/drawScale,stage.stageWidth/drawScale,10/drawScale);
			//天花板
			createFloor(0,0,stage.stageWidth/drawScale,10/drawScale);
			//左墙
			createFloor(0,0,10/drawScale,stage.stageHeight/drawScale);
			//右墙
			createFloor((stage.stageWidth-10)/drawScale,0,10/drawScale,stage.stageHeight/drawScale);
			//调试用的，估计，待研究
			drawDebug();
			addEventListener(Event.ENTER_FRAME, update);
			//让我很奇怪的是为什么监听不到鼠标事件
			stage.addEventListener(MouseEvent.CLICK, generateBody);
		}
		private function createFloor($x:Number,$y:Number,$w:Number,$h:Number):void
		{
			var shape:b2PolygonShape = new b2PolygonShape();
			shape.SetAsBox($w,$h);
			var fixture:b2FixtureDef = new b2FixtureDef();
			fixture.density = 1;
			fixture.friction = 1;
			fixture.shape = shape;
			fixture.restitution = 1;
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.type = b2Body.b2_staticBody;
			bodyDef.position.Set($x,$y);
			var floor:b2Body = world.CreateBody(bodyDef);
			floor.CreateFixture(fixture);
		}
		private function generateBody(e:MouseEvent=null):void
		{
			var shape:b2CircleShape = new b2CircleShape(10/drawScale);
			
			var fixture:b2FixtureDef = new b2FixtureDef();
			fixture.density = 1;
			fixture.friction = 2;
			fixture.restitution = 0.1;
			fixture.shape = shape;
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.type = b2Body.b2_dynamicBody;
			bodyDef.position.Set(this.mouseX/drawScale, this.mouseY/drawScale);
			var body:b2Body = world.CreateBody(bodyDef);
			body.CreateFixture(fixture);
		}
		
		private function update(e:Event):void
		{
			world.Step(1/drawScale,10,10);
			world.ClearForces();
			world.DrawDebugData();
			world.SetGravity(new b2Vec2(5-Math.random()*10, 5-Math.random()*10));
		}
		private function drawDebug():void
		{
			var debugDraw:b2DebugDraw = new b2DebugDraw();
			var debugSprite:Sprite = new Sprite();
			addChild(debugSprite);//讲debugdraw的关联视图添加到舞台上
			debugDraw.SetSprite(debugSprite);//关联sprite到debugdraw
			debugDraw.SetDrawScale(drawScale);//设置debugdraw的比例
			debugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);//？
			debugDraw.SetFillAlpha(0.5);//设置背景填充透明度
			world.SetDebugDraw(debugDraw);//关联世界
		}
	}
}

　　将重力改成随机的了，蛮好玩的