android 2d物理引擎-Box2d

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程序很简单：蓝色的是地面，从上面掉下两个绿球和一个红色的方块，它们之间的碰撞都由box2d引擎自己来完成。

（这程序运行起来有点卡，我 也正在解决这个问题，有朋友知道答案的也请分享一下啦！）

代码如下：

package?com.ray.test; ????import?org.jbox2d.collision.AABB; ?? import?org.jbox2d.collision.CircleDef; ?? import?org.jbox2d.collision.PolygonDef; ?? import?org.jbox2d.common.Vec2; ?? import?org.jbox2d.dynamics.Body; ?? import?org.jbox2d.dynamics.BodyDef; ?? import?org.jbox2d.dynamics.World; ?? ??import?android.app.Activity; ?? import?android.content.Context; ?? import?android.graphics.Canvas; ?? import?android.graphics.Color; ?? import?android.graphics.Paint; ?? import?android.os.Bundle; ?? import?android.os.Handler; ?? import?android.view.View; ?? import?android.view.Window; ?? import?android.view.WindowManager; ?? ??public?class?MyBox2d?extends?Activity?{ ?? ???? ??????private?final?static?int?RATE?=?10;//屏幕到现实世界的比例?10px：1m; ?? ????private?AABB?worldAABB;//创建?一个管理碰撞的世界 ?? ????private?World?world; ?? ????private?float?timeStep?=?1/60;//模拟的的频率 ?? ????private?int?iterations?=?10;//迭代越大，模拟约精确，但性能越低 ?? ????private?Body?body,body2,body3; ?? ????private?MyView?myView; ?? ????private?Handler?mHandler; ?? ????public?void?onCreate(Bundle?savedInstanceState)?{ ?? ????????super.onCreate(savedInstanceState); ?? ????????requestWindowFeature(Window.FEATURE_NO_TITLE); ??????????getWindow().setFlags(WindowManager.LayoutParams.?FLAG_FULLSCREEN?, ??????????WindowManager.LayoutParams.?FLAG_FULLSCREEN); ?????????? ??????????worldAABB?=?new?AABB(); ?? ????????? ?????????//上下界，以屏幕的左上方为?原点，如果创建的刚体到达屏幕的边缘的话，会停止模拟 ?? ????????worldAABB.lowerBound.set(-100.0f,-100.0f)； ?? ????????worldAABB.upperBound.set(100.0f,?100.0f);//注意这里使用的是现实世界的单位 ?? ???????? ??????????Vec2?gravity?=?new?Vec2(0.0f,10.0f); ?? ????????boolean?doSleep?=?true; ?? ???????? ????????????world?=?new?World(worldAABB,?gravity,?doSleep);//创建世界 ?? ???????? ??????????createBox(160,?470,?160,?10,?true);????? ?? ????????createBox1(160,?150,?160,?10,?false); ?? ???????? ??????????createCircle(160,?100,?10); ?? ????????createCircle1(150,?60,?10); ?? ????????timeStep?=?1.0f/60.0f; ?? ????????iterations?=?10; ?? ???????? ??????????myView?=?new?MyView(this); ?? ????????setContentView(myView); ??????????mHandler?=?new?Handler(); ?? ????????mHandler.post(update); ??????} ?????? ??????private?Runnable?update?=?new?Runnable()?{ ?? ????????public?void?run()?{ ?? ????????????????world.step(timeStep,?iterations);//开始模拟 ?? ????????????????Vec2?position?=?body.getPosition(); ??????????????????Vec2?position1?=?body2.getPosition(); ??????????????????Vec2?position2?=?body3.getPosition(); ??????????????????myView.x=position.x*RATE; ??????????????????myView.y=position.y*RATE; ?????????????????? ??????????????????myView.x1=position1.x*RATE;? ??????????????????myView.y1=position1.y*RATE; ?????????????????? ??????????????????myView.x2=position2.x*RATE; ??????????????????myView.y2=position2.y*RATE; ??????????????????myView.update(); ??????????????????mHandler.postDelayed(update,?(long)timeStep*1000); ?? ????????} ??????}; ?????? ??????public?void?createBox(float?x,float?y,float?half_width,float?half_height, ?? ?????????????????????boolean?isStatic){? ?? ????????PolygonDef?shape?=?new?PolygonDef(); ?? ????????if(isStatic){shape.density?=?0;} ?? ????????else{shape.density?=?2.0f;} ?? ????????shape.friction?=?0.8f; ?? ????????shape.restitution?=?0.3f; ?? ????????shape.setAsBox(half_width/RATE,?half_height/RATE); ?????????? ??????????BodyDef?bodyDef?=?new?BodyDef(); ?? ????????bodyDef.position.set(x/RATE,?y/RATE); ??????????Body?body1=?world.createBody(bodyDef); ??????????body1.createShape(shape); ??????????body1.setMassFromShapes(); ??????} ?????? ??????public?void?createCircle(float?x,float?y,float?radius){ ?? ????????CircleDef?shape?=?new?CircleDef(); ?? ????????shape.density?=?7; ?? ????????shape.friction?=?0.2f; ?? ????????shape.radius?=?radius/RATE; ?????????? ??????????BodyDef?bodyDef?=?new?BodyDef(); ?? ????????bodyDef.position.set(x/RATE,?y/RATE); ??????????body2?=?world.createBody(bodyDef); ??????????body2.createShape(shape); ??????????body2.setMassFromShapes(); ??????} ?????? ??????public?void?createCircle1(float?x,float?y,float?radius){ ?? ????????CircleDef?shape?=?new?CircleDef(); ?? ????????shape.density?=?7; ?? ????????shape.friction?=?0.2f; ?? ????????shape.radius?=?radius/RATE; ?????????? ??????????BodyDef?bodyDef?=?new?BodyDef(); ?? ????????bodyDef.position.set(x/RATE,?y/RATE); ??????????body3?=?world.createBody(bodyDef); ??????????body3.createShape(shape); ??????????body3.setMassFromShapes(); ??????} ?????? ??????public?void?createBox1(float?x,float?y,float?half_width,float?half_height, ?? ???????????????????boolean?isStatic){? ?? ????????PolygonDef?shape?=?new?PolygonDef(); ?? ????????if(isStatic){shape.density?=?0;} ?? ????????else{shape.density?=?2.0f;} ?? ????????shape.friction?=?0.3f; ?? ????????shape.setAsBox(half_width/RATE,?half_height/RATE); ?????????? ??????????BodyDef?bodyDef?=?new?BodyDef(); ?? ????????bodyDef.position.set(x/RATE,?y/RATE); ??????????body=?world.createBody(bodyDef); ??????????body.createShape(shape); ??????????body.setMassFromShapes(); ??????} ?????? ??????class?MyView?extends?View{ ?? ????????Canvas?canvas; ??????????public?float?x=160,y=150; ?? ????????public?float?x1=160,y1=100; ?? ????????public?float?x2=150,y2=60; ?? ????????public?MyView(Context?context)?{ ?? ????????????super(context); ?? ????????} ????????????public?void?drawBox(float?x,float?y){ ?? ????????????Paint?mPaint?=?new?Paint(); ?? ????????????mPaint.setAntiAlias(true); ?? ????????????mPaint.setColor(Color.RED); ??????????????canvas.drawRect(x-160,?y-10,?x+160,?y+10,?mPaint); ?? ????????} ?????????? ??????????public?void?drawGround(){ ?? ????????????Paint?mPaint?=?new?Paint(); ?? ????????????mPaint.setAntiAlias(true); ?? ????????????mPaint.setColor(Color.BLUE); ??????????????canvas.drawRect(0,?460,?320,?480,?mPaint); ?? ????????} ?????????? ??????????public?void?drawCircle(float?x1,float?y1){ ?? ????????????Paint?mPaint?=?new?Paint(); ?? ????????????mPaint.setAntiAlias(true); ?? ????????????mPaint.setColor(Color.GREEN); ??????????????canvas.drawCircle(x1,?y1,?10,?mPaint); ?? ????????} ?????????? ??????????public?void?update(){ ?? ????????????postInvalidate(); ??????????} ?????????? ??????????protected?void?onDraw(Canvas?canvas)?{ ?? ????????????super.onDraw(canvas); ?? ????????????this.canvas?=?canvas; ?? ????????????drawGround(); ??????????????drawBox(x,?y); ??????????????drawCircle(x1,?y1); ??????????????drawCircle(x2,?y2); ??????????} ?????????? ?????????? ??????} ??}??

?程序运行的时候需要加载Jbox2d的库，可到以下地址下载（使用的是不带渲染部分的库jbox2d-2.0.1-library-only.jar）：

http://sourceforge.net/projects/jbox2d/ 附件也有