学步园

   因为时间比较急，故此只能快速寻找一些资料看。发现使用box2D 2.1a 版本确实和之前发生兼容性问题，实现拖拽真不容易，完全看不懂。先记录一下其他人写的拖拽部分代码。这部分代码加入到HelloWorld 里面去。多少有点长了 不容易学习。

package<br /> {<br /> import flash.display.Sprite;<br /> import flash.events.*;<br /> import Box2D.Dynamics.*;<br /> import Box2D.Collision.*;<br /> import Box2D.Collision.Shapes.*;<br /> import Box2D.Common.Math.*;<br /> import Box2D.Dynamics.Joints.*;<br /> import Box2D.Dynamics.Controllers.*;</p> <p> public class HelloWorld extends Sprite<br /> {</p> <p> //程序入口，创建一个世界<br /> private var world:b2World = new b2World(new b2Vec2(0,10.0),true);</p> <p> private var worldScale:int = 30;//30像素=1米<br /> private static const vesion:String="box2d for 2.1a";</p> <p> private var mouseJoint:b2MouseJoint;<br /> public function HelloWorld()<br /> {<br /> debugDraw();<br /> drawBox(250,300,500,50,false);<br /> drawBox(250,100,100,100,true);<br /> drawCircle(100,100,50,true);<br /> addEventListener(Event.ENTER_FRAME, updateHandler);<br /> stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDownHandler);</p> <p> }</p> <p> //绘制一个矩形<br /> private function drawBox(x:Number,y:Number,width:Number,height:Number,isDynamic:Boolean):void<br /> {<br /> var bodyDef:b2BodyDef= new b2BodyDef();<br /> bodyDef.position.Set(x/worldScale, y/worldScale);<br /> if (isDynamic)<br /> {<br /> bodyDef.type = b2Body.b2_dynamicBody;<br /> }<br /> var box:b2PolygonShape = new b2PolygonShape();<br /> box.SetAsBox(width/2/worldScale, height/2/worldScale);</p> <p> var fixtureDef:b2FixtureDef = new b2FixtureDef();<br /> fixtureDef.shape = box;</p> <p> var body:b2Body = world.CreateBody(bodyDef);<br /> body.CreateFixture(fixtureDef);<br /> }</p> <p> //绘制一个圆<br /> private function drawCircle(x:Number,y:Number,radius:Number,isDynamic:Boolean):void<br /> {<br /> var bodyDef:b2BodyDef= new b2BodyDef();<br /> bodyDef.position.Set(x/worldScale, y/worldScale);<br /> if (isDynamic)<br /> {<br /> bodyDef.type = b2Body.b2_dynamicBody;<br /> }<br /> var circle:b2CircleShape=new b2CircleShape(radius/worldScale);</p> <p> var fixtureDef:b2FixtureDef = new b2FixtureDef();<br /> fixtureDef.shape = circle;</p> <p> var body:b2Body = world.CreateBody(bodyDef);<br /> body.CreateFixture(fixtureDef);<br /> }</p> <p> private function debugDraw():void<br /> {<br /> var _debugDraw:b2DebugDraw=new b2DebugDraw();<br /> var sprite:Sprite=new Sprite();<br /> addChild(sprite);<br /> _debugDraw.SetSprite(sprite);<br /> _debugDraw.SetDrawScale(worldScale);<br /> _debugDraw.SetFlags(b2DebugDraw.e_shapeBit);<br /> world.SetDebugDraw(_debugDraw);<br /> }</p> <p> //交互的过程由四个步骤完成：<br /> //第一步：获取鼠标单击处的刚体。<br /> //第二步：创建鼠标关节。<br /> //第三步：控制鼠标关节。<br /> //第四步：销毁鼠标关节。<br /> private function getBodyAtMouse(includeStatic:Boolean=false):b2Body<br /> {<br /> var mouseXWorldPhys:Number = (mouseX)/worldScale;<br /> var mouseYWorldPhys:Number = (mouseY)/worldScale;<br /> var mousePVec:b2Vec2 = new b2Vec2();<br /> mousePVec.Set(mouseXWorldPhys, mouseYWorldPhys);<br /> var aabb:b2AABB = new b2AABB();<br /> aabb.lowerBound.Set(mouseXWorldPhys - 0.001, mouseYWorldPhys - 0.001);<br /> aabb.upperBound.Set(mouseXWorldPhys + 0.001, mouseYWorldPhys + 0.001);</p> <p> var body:b2Body = null;<br /> function query(fix:b2Fixture):Boolean {<br /> var shape:b2Shape = b2Fixture(fix).GetShape();<br /> if (fix.GetBody().GetType() != b2Body.b2_staticBody || includeStatic) {<br /> var inside:Boolean = b2Shape(shape).TestPoint(fix.GetBody().GetTransform(), mousePVec);<br /> if (inside) {<br /> body = fix.GetBody();<br /> return false;<br /> }<br /> }<br /> return true;<br /> }<br /> world.QueryAABB(query, aabb);<br /> return body;<br /> }</p> <p> private function onMouseDownHandler(event:MouseEvent):void<br /> {<br /> var mouseJoinDef:b2MouseJointDef;<br /> var body:b2Body = this.getBodyAtMouse();<br /> if (body)<br /> {<br /> mouseJoinDef = new b2MouseJointDef();<br /> mouseJoinDef.bodyA = world.GetGroundBody();</p> <p> mouseJoinDef.bodyB = body;<br /> mouseJoinDef.target.Set((mouseX / worldScale), (mouseY / worldScale));<br /> mouseJoinDef.maxForce = 10000;<br /> this.mouseJoint = (world.CreateJoint(mouseJoinDef) as b2MouseJoint);<br /> }<br /> stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUpHandler);<br /> }<br /> private function onMouseUpHandler(event:MouseEvent):void<br /> {<br /> stage.removeEventListener(MouseEvent.MOUSE_UP, onMouseUpHandler);<br /> if (this.mouseJoint)<br /> {<br /> world.DestroyJoint(this.mouseJoint);<br /> this.mouseJoint = null;<br /> }<br /> }</p> <p> private function updateHandler(event:Event):void<br /> {<br /> world.Step(1/30,10,10);<br /> world.ClearForces();<br /> world.DrawDebugData();</p> <p> //拖拽部分<br /> if (mouseJoint) {<br /> var mouseXWorldPhys:Number = mouseX / worldScale;<br /> var mouseYWorldPhys:Number = mouseY / worldScale;<br /> var p2:b2Vec2=new b2Vec2(mouseXWorldPhys,mouseYWorldPhys);<br /> mouseJoint.SetTarget(p2);<br /> }<br /> }<br /> }<br /> }

其中这几部分是拖拽的，是由一些网友书写。借用一下。

//交互的过程由四个步骤完成：<br /> //第一步：获取鼠标单击处的刚体。<br /> //第二步：创建鼠标关节。<br /> //第三步：控制鼠标关节。<br /> //第四步：销毁鼠标关节。<br /> private function getBodyAtMouse(includeStatic:Boolean=false):b2Body<br /> {<br /> var mouseXWorldPhys:Number = (mouseX)/worldScale;<br /> var mouseYWorldPhys:Number = (mouseY)/worldScale;<br /> var mousePVec:b2Vec2 = new b2Vec2();<br /> mousePVec.Set(mouseXWorldPhys, mouseYWorldPhys);<br /> var aabb:b2AABB = new b2AABB();<br /> aabb.lowerBound.Set(mouseXWorldPhys - 0.001, mouseYWorldPhys - 0.001);<br /> aabb.upperBound.Set(mouseXWorldPhys + 0.001, mouseYWorldPhys + 0.001);</p> <p> var body:b2Body = null;<br /> function query(fix:b2Fixture):Boolean {<br /> var shape:b2Shape = b2Fixture(fix).GetShape();<br /> if (fix.GetBody().GetType() != b2Body.b2_staticBody || includeStatic) {<br /> var inside:Boolean = b2Shape(shape).TestPoint(fix.GetBody().GetTransform(), mousePVec);<br /> if (inside) {<br /> body = fix.GetBody();<br /> return false;<br /> }<br /> }<br /> return true;<br /> }<br /> world.QueryAABB(query, aabb);<br /> return body;<br /> }</p> <p> private function onMouseDownHandler(event:MouseEvent):void<br /> {<br /> var mouseJoinDef:b2MouseJointDef;<br /> var body:b2Body = this.getBodyAtMouse();<br /> if (body)<br /> {<br /> mouseJoinDef = new b2MouseJointDef();<br /> mouseJoinDef.bodyA = world.GetGroundBody();</p> <p> mouseJoinDef.bodyB = body;<br /> mouseJoinDef.target.Set((mouseX / worldScale), (mouseY / worldScale));<br /> mouseJoinDef.maxForce = 10000;<br /> this.mouseJoint = (world.CreateJoint(mouseJoinDef) as b2MouseJoint);<br /> }<br /> stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUpHandler);<br /> }<br /> private function onMouseUpHandler(event:MouseEvent):void<br /> {<br /> stage.removeEventListener(MouseEvent.MOUSE_UP, onMouseUpHandler);<br /> if (this.mouseJoint)<br /> {<br /> world.DestroyJoint(this.mouseJoint);<br /> this.mouseJoint = null;<br /> }<br /> }

//拖拽部分<br /> if (mouseJoint) {<br /> var mouseXWorldPhys:Number = mouseX / worldScale;<br /> var mouseYWorldPhys:Number = mouseY / worldScale;<br /> var p2:b2Vec2=new b2Vec2(mouseXWorldPhys,mouseYWorldPhys);<br /> mouseJoint.SetTarget(p2);<br /> }

通过这些设置 可以实现拖拽，同时也有一些人 封装了一个类对其方便调用。不妨可以修改一下

注意：2.1a版本改过命名。

 过去版本：

mouseJoinDef.body1 =  world.GetGroundBody();
mouseJoinDef.body2 = body;

改成了bodyA 和bodyB 属性

mouseJoinDef.bodyA =  world.GetGroundBody();
mouseJoinDef.bodyB = body;

有部分属性取消了。在编译过程如果使用低版本的和高级 版本不一样了。