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。