package { import Box2D.Collision.Shapes.*; import Box2D.Collision.*; import Box2D.Common.*; import Box2D.Common.Math.*; import Box2D.Dynamics.*; import flash.display.Sprite; import flash.display.StageScaleMode; import flash.display.StageAlign; import flash.events.Event; import flash.events.MouseEvent; [SWF(backgroundColor="0x333333",width="550",height="400",frameRate="30")] public class ClickBox2DNew extends Sprite { private var world:b2World; private var physScale:Number = 30.0; private var m_timeStep:Number = 1.0 / 30.0; private var m_iteration:int = 10; private var body:b2Body; private var bodyDef:b2BodyDef; private var boxShape:b2PolygonDef; private var circleShape:b2CircleDef; public function ClickBox2DNew() { stage.align = StageAlign.TOP_LEFT; stage.scaleMode = StageScaleMode.NO_SCALE; init(); } private function init():void { addEventListener(Event.ENTER_FRAME, onFrame); addEventListener(MouseEvent.MOUSE_DOWN, onDown); var worldAABB:b2AABB = new b2AABB(); worldAABB.lowerBound.Set( -100.0, -100.0); worldAABB.upperBound.Set(100.0, 100.0); var gravity:b2Vec2 = new b2Vec2(0.0, 10.0); var doSleep:Boolean = true; world = new b2World(worldAABB, gravity, doSleep); //创建地面 createBox(550 / 2, 390,0, 275, 10, true); //左右挡板 createBox(0,400/2,0,10,200,true); createBox(550, 400 / 2,0, 10, 200, true); //障碍物 createBox(Math.random() * 250 + 100, Math.random() * 150 + 100, Math.random()*360,Math.random() * 50, Math.random() * 50, true); createBox(Math.random() * 250 + 100, Math.random() * 150 + 100, Math.random()*360,Math.random() * 50, Math.random() * 50, true); } private function onFrame(e:Event):void { world.Step(m_timeStep, m_iteration); for (var b:b2Body = world.m_bodyList; b;b=b.m_next ) { if (b.m_userData is Sprite) { b.m_userData.x = b.GetPosition().x * physScale; b.m_userData.y = b.GetPosition().y * physScale; b.m_userData.rotation = b.GetAngle() * 180 / Math.PI; } } } private function onDown(e:MouseEvent):void { var tempNum:Number = Math.random(); var halfWidth:Number = 10 + Math.random() * 50; var halfHeight:Number = 10 + Math.random() * 50; var xPos:Number = 100+Math.random() * (stage.stageWidth-100); var yPos:Number = 0; var radius:Number = 10 + Math.random() * 30; var angle:Number = Math.random() * 360; if (tempNum>.5) { createBox(xPos,yPos,angle,halfWidth,halfHeight,false); } else { createCircle(xPos,yPos,radius); } } private function createCircle(xPos:Number,yPos:Number,radius:Number):void { circleShape = new b2CircleDef(); circleShape.density = 7; circleShape.friction = 0.3; circleShape.restitution = 0.4; circleShape.radius = radius / physScale; bodyDef = new b2BodyDef(); bodyDef.userData = new Ball(radius, 0xffffff * Math.random()); //bodyDef.userData.width = radius * 2; //bodyDef.userData.height = radius * 2; bodyDef.position.Set(xPos / physScale, yPos / physScale); body = world.CreateBody(bodyDef); body.CreateShape(circleShape); body.SetMassFromShapes(); addChild(bodyDef.userData); } private function createBox(xPos:Number,yPos:Number,angle:Number,halfWidth:Number,halfHeight:Number,isStatic:Boolean):void { boxShape = new b2PolygonDef(); if (isStatic) { boxShape.density = 0.0; } else { boxShape.density = 2.0; } boxShape.friction = 0.3; boxShape.restitution = 0.4; boxShape.SetAsBox(halfWidth / physScale, halfHeight / physScale); bodyDef = new b2BodyDef(); bodyDef.angle = angle; bodyDef.userData = new Box(halfWidth * 2, halfHeight * 2, 0xffffff * Math.random()); bodyDef.position.Set(xPos / physScale, yPos/physScale); body = world.CreateBody(bodyDef); body.CreateShape(boxShape); body.SetMassFromShapes(); addChild(bodyDef.userData); } } }
说明：
Box2D会自动管理各个物体的碰撞，弹跳等物理状态，我们只需要创建各种刚体。创建刚体可以通过b2BodyDef.userData来创建。 b2Shape.SetAsBox(width,height)指的是物体的半宽和半高，所以在计算时都要乘以2。由于Box2D本身的限制，运算时要进行长度换算。&QEj*Gv*K,~:|r0
4zE9H4i%_-W0 代码中的Box和Ball类都是注册中心在其几何中心，我就不提供代码了，这两个类主要是画矩形和圆形，很简单大家自己写。你也可以在FlashIDE中画出自己的方形和圆形来，然后给一个类名，然后从库里链接。
虽然是由主类监听单击事件，但在Box2D虚拟世界里是没有没有可以显示的类的~只要单击虚拟世界中任何一个物体就会触发单击事件，即产生一个随机方形或者圆形。
原文地址：http://space.flash8.net/space/?628770/viewspace-432180.html
