本文实例讲述了Android游戏开发学习之引擎用法。分享给大家供大家参考。具体如下：
汽车引擎是汽车的心脏，其决定了汽车的性能和稳定性，是人们在购车时相当关注的。而游戏中的物理引擎就如汽车的引擎一样，占据了非常重要的位置。一款好的物理引擎可以非常真实地模拟现实世界，使得游戏更加逼真，提供更好的娱乐体验。
一、JBox2D简介
JBox2D是开源物理引擎Box2D的Java版本，可以直接用于Android。由于JBox2D的图形渲染使用的是Processing库，因此在Android平台上使用JBox2D时，图形渲染工作只能自行开发。该引擎能够根据开发人员设定的参数，如重力、密度、摩擦系数和弹性系数等，自动地进行2D刚体物理运动的全方位模拟。
二、示例
1.小球弹跳进阶版
在第1节中小球的下落、碰撞、弹起都是用代码来维护的，下面使用物理引擎来实现，并且加入了刚体之间的碰撞。
(1)常量类Constant
package box2d.bheap; public class Constant { public static final float RATE=10; //屏幕与现实世界的比例 public static final boolean DRAW_THREAD_FLAG=true; //绘制线程工作标识位 public static final float TIME_STEP=2.0f/60.0f; //模拟的频率 public static final int ITERA=10; //迭代次数 public static int SCREEN_WIDTH; //屏幕宽度 public static int SCREEN_HEIGHT; //屏幕高度 }(2)抽象类MyBody
该类为自定义的抽象类，是所有自定义刚体类的基类。由于JBox2D中的刚体类对象仅具有物理仿真计算的功能，并没有提供Android平台下的绘制功能，直接使用不是很方便。因此，这里定义了MyBody对自定义刚体的绘制及JBox2D物理仿真对象进行了封装。
package box2d.bheap; import org.jbox2d.dynamics.Body; import android.graphics.Canvas; import android.graphics.Paint; public abstract class MyBody { Body body; //JBox2D物理引擎中的刚体 int color; //刚体的颜色 public abstract void drawSelf(Canvas canvas,Paint paint); //绘制的方法 }(3)圆形刚体类MyCircleColor
package box2d.bheap; import org.jbox2d.dynamics.Body; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Paint.Style; import static box2d.bheap.Constant.*; //静态导入 public class MyCircleColor extends MyBody { float radius; //圆形半径 public MyCircleColor(Body body,float radius,int color) { this.body=body; this.radius=radius; this.color=color; } @Override public void drawSelf(Canvas canvas, Paint paint) { paint.setColor(color&0xCFFFFFF); //设置颜色 float x=body.getPosition().x*RATE; float y=body.getPosition().y*RATE; canvas.drawCircle(x, y, radius, paint); //画圆 paint.setStyle(Style.STROKE); //设置空心无填充 paint.setStrokeWidth(1); paint.setColor(color); //画边 canvas.drawCircle(x, y, radius, paint); paint.reset(); //恢复画笔设置 } }(4)矩形刚体类MyRectColor
package box2d.bheap; import static box2d.bheap.Constant.RATE; import org.jbox2d.dynamics.Body; import android.graphics.Canvas; import android.graphics.Matrix; import android.graphics.Paint; public class MyRectColor extends MyBody { float halfWidth;//半宽 float halfHeight;//半高 public MyRectColor(Body body,float halfWidth,float halfHeight,int color) { this.body=body; this.halfWidth=halfWidth; this.halfHeight=halfHeight; this.color=color; } public void drawSelf(Canvas canvas,Paint paint) { paint.setColor(color&0x8CFFFFFF); float x=body.getPosition().x*RATE; float y=body.getPosition().y*RATE; float angle=body.getAngle(); canvas.save(); Matrix m1=new Matrix(); m1.setRotate((float)Math.toDegrees(angle),x, y); canvas.setMatrix(m1); canvas.drawRect(x-halfWidth, y-halfHeight, x+halfWidth, y+halfHeight, paint); paint.setStyle(Paint.Style.STROKE); paint.setStrokeWidth(1);//设置线条宽度 paint.setColor(color); canvas.drawRect(x-halfWidth, y-halfHeight, x+halfWidth, y+halfHeight, paint); paint.reset(); canvas.restore(); } }(5)生成刚体形状的工具类Box2DUtil
package box2d.bheap; import static box2d.bheap.Constant.RATE; import org.jbox2d.collision.CircleDef; import org.jbox2d.collision.PolygonDef; import org.jbox2d.dynamics.Body; import org.jbox2d.dynamics.BodyDef; import org.jbox2d.dynamics.World; public class Box2DUtil { /** * 创建矩形物体（颜色） */ public static MyRectColor createBox ( float x, float y, float halfWidth, float halfHeight, boolean isStatic, //是否为静止的 World world, int color ) { PolygonDef shape=new PolygonDef(); //创建多边形描述对象 if(isStatic) { shape.density=0; } else { shape.density=1.0f; } shape.friction=0.0f; //设置摩擦系数 shape.restitution=0.6f; //设置能量损失率 shape.setAsBox(halfWidth/RATE, halfHeight/RATE); BodyDef bodyDef=new BodyDef(); //创建刚体描述对象 bodyDef.position.set(x/RATE,y/RATE); //设置位置 Body bodyTemp=world.createBody(bodyDef); //在世界中创建刚体 bodyTemp.createShape(shape); //指定刚体形状 bodyTemp.setMassFromShapes(); //设置物体质量 return new MyRectColor(bodyTemp, halfWidth, halfHeight, color); } /** * 创建圆形物体（颜色） */ public static MyCircleColor createCircle ( float x, float y, float radius, World world, int color ) { CircleDef shape=new CircleDef(); //创建圆描述对象 shape.density=2; //设置密度 shape.friction=0.0f; //设置摩擦系数 shape.restitution=0.95f; //设置能量损失率 shape.radius=radius/RATE;//设置半径 BodyDef bodyDef=new BodyDef(); //创建刚体描述对象 bodyDef.position.set(x/RATE,y/RATE); //设置位置 Body bodyTemp=world.createBody(bodyDef); //在世界中创建刚体 bodyTemp.createShape(shape); //指定刚体形状 bodyTemp.setMassFromShapes(); //设置物体质量 return new MyCircleColor(bodyTemp, radius, color); } }(6)颜色工具类ColorUtil
package box2d.bheap; public class ColorUtil { static int[][] result= { {56,225,254}, {41,246,239}, {34,244,197}, {44,241,161}, {65,239,106}, {45,238,59}, {73,244,51}, {99,233,58}, {129,243,34}, {142,245,44}, {187,243,32}, {232,250,28}, {242,230,46}, {248,196,51}, {244,125,31}, {247,88,46}, {249,70,40}, {249,70,40}, {248,48,48}, {250,30,30}, {252,15,15}, {255,0,0}, }; public static int getColor(int index) { int[] rgb=result[index%result.length]; int result=0xff000000; result=result|(rgb[0]<<16); result=result|(rgb[1]<<8); result=result|(rgb[2]); return result; } }(7)主控制类MyBox2dActivity
package box2d.bheap; import java.util.ArrayList; import java.util.Random; import org.jbox2d.collision.AABB; import org.jbox2d.common.Vec2; import org.jbox2d.dynamics.World; import android.app.Activity; import android.content.pm.ActivityInfo; import android.os.Bundle; import android.util.DisplayMetrics; import android.view.Window; import android.view.WindowManager; import static box2d.bheap.Constant.*; public class MyBox2dActivity extends Activity { AABB worldAABB;//创建 一个管理碰撞的世界 World world; Random random=new Random(); //物体列表 ArrayList<MyBody> bl=new ArrayList<MyBody>(); public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //设置为全屏 requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams. FLAG_FULLSCREEN , WindowManager.LayoutParams. FLAG_FULLSCREEN); //设置为横屏模式 setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); //获取屏幕尺寸 DisplayMetrics dm=new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(dm); if(dm.widthPixels<dm.heightPixels) { SCREEN_WIDTH=dm.widthPixels; SCREEN_HEIGHT=dm.heightPixels; } else { SCREEN_WIDTH=dm.heightPixels; SCREEN_HEIGHT=dm.widthPixels; } 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; //创建世界 world = new World(worldAABB, gravity, doSleep); //创建4边 final int kd=40;//宽度或高度 MyRectColor mrc=Box2DUtil.createBox(kd/4, SCREEN_HEIGHT/2, kd/4, SCREEN_HEIGHT/2, true,world,0xFFe6e4FF); bl.add(mrc); mrc=Box2DUtil.createBox(SCREEN_WIDTH-kd/4, SCREEN_HEIGHT/2, kd/4, SCREEN_HEIGHT/2, true,world,0xFFe6e4FF); bl.add(mrc); mrc=Box2DUtil.createBox(SCREEN_WIDTH/2, kd/4, SCREEN_WIDTH/2, kd/4, true,world,0xFFe6e4FF); bl.add(mrc); mrc=Box2DUtil.createBox(SCREEN_WIDTH/2, SCREEN_HEIGHT-kd/4, SCREEN_WIDTH/2, kd/4, true,world,0xFFe6e4FF); bl.add(mrc); //创建砖块 //砖块间距 行间距为20 模块宽度为10 最多一行为9块 final int bs=20; final int bw=(int)((SCREEN_WIDTH-2*kd-11*bs)/18); //============================================================ for(int i=2;i<10;i++) { if((i%2)==0) { //左侧蓝木块 for(int j=0;j<9-i;j++) { mrc=Box2DUtil.createBox ( kd/2+bs+bw/2+i*(kd+5)/2+j*(kd+5)+3, SCREEN_HEIGHT+bw-i*(bw+kd)/2, bw/2, kd/2, false, world, ColorUtil.getColor(Math.abs(random.nextInt())) ); bl.add(mrc); } //右侧蓝木块 for(int j=0;j<9-i;j++) { mrc=Box2DUtil.createBox ( 3*kd/2+bs-bw/2+i*(kd+5)/2+j*(kd+5)-3, SCREEN_HEIGHT+bw-i*(bw+kd)/2, bw/2, kd/2, false, world, ColorUtil.getColor(Math.abs(random.nextInt())) ); bl.add(mrc); } } if((i%2)!=0) { for(int j=0;j<10-i;j++) { mrc=Box2DUtil.createBox ( kd/2+bs+kd/2+(i-1)*(kd+5)/2+j*(kd+5), SCREEN_HEIGHT-(kd-bw)/2-(i-1)*(bw+kd)/2, kd/2, bw/2, false, world, ColorUtil.getColor(Math.abs(random.nextInt())) ); bl.add(mrc); } } } mrc=Box2DUtil.createBox ( 5*kd+bs+20, SCREEN_HEIGHT-(kd+bw)*4-kd, bw/2, kd/2, false, world, ColorUtil.getColor(Math.abs(random.nextInt())) ); bl.add(mrc); //创建球 MyCircleColor ball=Box2DUtil.createCircle(SCREEN_WIDTH/2-24, kd, kd/2, world,ColorUtil.getColor(Math.abs(random.nextInt()))); bl.add(ball); ball.body.setLinearVelocity(new Vec2(0,50)); GameView gv= new GameView(this); setContentView(gv); }}(8)显示界面类GameView
package box2d.bheap;import android.graphics.Canvas; import android.graphics.Paint; import android.view.SurfaceHolder; import android.view.SurfaceHolder.Callback; import android.view.SurfaceView; public class GameView extends SurfaceView implements Callback{ MyBox2dActivity activity; Paint paint; DrawThread dt; public GameView(MyBox2dActivity activity) { super(activity); this.activity=activity; this.getHolder().addCallback(this); paint =new Paint(); paint.setAntiAlias(true); dt=new DrawThread(this); dt.start(); } public void onDraw(Canvas canvas) { if(canvas==null) { return ; } canvas.drawARGB(255, 255, 255, 255); //设置背景颜色白色 for (MyBody mb : activity.bl) { mb.drawSelf(canvas, paint); } } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } @Override public void surfaceCreated(SurfaceHolder holder) { repaint(); } @Override public void surfaceDestroyed(SurfaceHolder holder) { } public void repaint() { SurfaceHolder holder=this.getHolder(); Canvas canvas=holder.lockCanvas(); try { synchronized(holder){ onDraw(canvas); } } catch(Exception e){ e.printStackTrace(); } finally { if(canvas!=null) { holder.unlockCanvasAndPost(canvas); } } } }(9)绘制线程类DrawThread
package box2d.bheap; import static box2d.bheap.Constant.*; //绘制线程 public class DrawThread extends Thread { GameView gv; public DrawThread(GameView gv) { this.gv=gv; } @Override public void run() { while(DRAW_THREAD_FLAG) { gv.activity.world.step(TIME_STEP, ITERA);//开始模拟 gv.repaint(); try { Thread.sleep(20); } catch (InterruptedException e) { e.printStackTrace(); } } } }希望本文所述对大家的jsp程序设计有所帮助。
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