Android上使用Box2d
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转自http://blog.csdn.net/htttw/article/details/7600277
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
1.
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
2.
新建一个Android Project,如下所示:
2.
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);
- }
- }
- }
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); } }}
3.
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:
4.
在模拟器中运行就可以了,结果如下:
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?
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