Android下2d物理引擎Box2d用法简单实例

本文实例讲述了android下2d物理引擎box2d用法。分享给大家供大家参考。具体如下：

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/

package com.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);
 }
 }
}

希望本文所述对大家的android程序设计有所帮助。