Android上使用Box2d

Android上使用Box2d

Box2d是一个非常优秀的开源2D物理引擎，可以模拟出非常真实的物理效果，今天我们介绍如何在Andoird下使用Box2d：

注：本文的大部分参考：http://rayleung.iteye.com/blog/439056

Box2d原来使用c++写的，不过已经有了Java版本的：JBox2D，可以在http://sourceforge.net/projects/jbox2d/下载，一共有两个：

JBox2d-2.0.1.zip和JBox2D-2.0.1-b250-Full.jar。我的版本是2.0.1

新建一个Android Project，如下所示：

Android上使用Box2d_第1张图片

修改Jbox2dtestActivity.java文件如下：

package com.test.jbox2d;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 Jbox2dtestActivity 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);    }  }}

加入JBox2D.jar库：

在项目目录中新建一个libs文件夹，

解压JBox2d-2.0.1.zip，找到jbox2d-2.0.1-library-only.jar，加入libs文件夹中

然后右击项目，选择属性，在Java Build Path的Libraries中加入这个jar文件，如下如所示：

在模拟器中运行就可以了，结果如下：

Android上使用Box2d_第2张图片

不过在模拟器上运行会卡，在真机上也如此。并且运行程序时CPU使用率很高！不知如何解决？

完成！

更多相关文章

随机推荐