求助：添加 jobox2d后无法找到自己定义的MySurfaceView类

[hairelove]

如题，求高手解答
学习使用jobox2d时，在导入jobox2d包的时候，运行正常，导入jobox2d包后，在运行的时候，提示java.lang.NoClassDefFoundError: com.sky.game.MySurfaceView
代码如下：
MainActivit类

package com.sky.game;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		// 设置全屏
		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
				WindowManager.LayoutParams.FLAG_FULLSCREEN);
		// 去除应用程序标题
		this.requestWindowFeature(Window.FEATURE_NO_TITLE);
		// 设置竖屏
		setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
		//显示自定义MySurfaceView实例
		setContentView(new MySurfaceView(this));
    }
  //添加一个程序退出方法
  	public void exit() {
  		//退出应用程序
  		System.exit(0);
  	}
}

MySurfaceView类

//**
 * 
 */
package com.sky.game;

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.ContactListener;
import org.jbox2d.dynamics.World;
import org.jbox2d.dynamics.contacts.ContactPoint;
import org.jbox2d.dynamics.contacts.ContactResult;

import android.R.bool;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;

/**
 * @author sky
 *
 */
public class MySurfaceView extends SurfaceView implements Runnable, Callback ,ContactListener{

	//游戏状态
	private final int GANESTATE_MENU=0;
	private final int GANESTATE_HELP=1;
	private final int GANESTATE_GAMEING=2;
	private  int gameState=GANESTATE_MENU;
	private Canvas canvas;
	private Paint paint;
	private SurfaceHolder sfh;
	private Thread th;
	private boolean flag;
	private int screenW,screenH;
	// 菜单、按钮、游戏背景图片资源
	private Bitmap bmpIcon,bmpMenu_help, bmpMenu_play, bmpMenu_exit, bmpMenu_resume,
					bmpMenu_replay, bmp_menubg, bmp_gamebg, bmpMenuBack, bmp_smallbg,
					bmpMenu_menu, bmp_helpbg, bmpBody_lost, bmpBody_win, bmpWinbg,
					bmpLostbg;
	// 创建按钮
	private HButton hbHelp, hbPlay, hbExit, hbResume, hbReplay, hbBack, hbMenu;
	// Body图片资源
	private Bitmap bmpH, bmpS, bmpSh, bmpSs, bmpBall;
	// ----添加一个物理世界---->>
	private World world;
	private AABB aabb;
	private Vec2 gravity;
	private float timeStep=1f/60f;
	private int iterations=10;
	private final float RATE=30;
	public MySurfaceView(Context context) {
		super(context);
		sfh=this.getHolder();
		sfh.addCallback(this);
		paint=new Paint();
		paint.setColor(Color.WHITE);
		setFocusable(true);
		setFocusableInTouchMode(true);
		this.setKeepScreenOn(true);
		// --添加一个物理世界--->>
		aabb=new AABB();
		gravity=new Vec2(0,100);
		aabb.lowerBound.set(-100,100);
		aabb.upperBound.set(100,100);
		world=new World(aabb, gravity, true);
		// ---实例化Body图片资源
		bmpS=BitmapFactory.decodeResource(getResources(), R.drawable.s);
		bmpH=BitmapFactory.decodeResource(getResources(), R.drawable.h);
		bmpSh=BitmapFactory.decodeResource(getResources(), R.drawable.sh);
		bmpSs=BitmapFactory.decodeResource(getResources(), R.drawable.ss);
		bmpBall=BitmapFactory.decodeResource(getResources(), R.drawable.ball);
		// 实例菜单、按钮、游戏背景图片资源
		bmpIcon=BitmapFactory.decodeResource(getResources(), R.drawable.icon);
		bmp_gamebg=BitmapFactory.decodeResource(getResources(), R.drawable.game_bg);
		bmp_helpbg=BitmapFactory.decodeResource(getResources(), R.drawable.helpbg);
		bmp_menubg=BitmapFactory.decodeResource(getResources(), R.drawable.menu_bg);
		bmp_smallbg=BitmapFactory.decodeResource(getResources(), R.drawable.smallbg);
		bmpBody_lost=BitmapFactory.decodeResource(getResources(), R.drawable.lostbody);
		bmpBody_win=BitmapFactory.decodeResource(getResources(), R.drawable.winbody);
		bmpLostbg=BitmapFactory.decodeResource(getResources(), R.drawable.gamelost);
		bmpMenu_exit=BitmapFactory.decodeResource(getResources(), R.drawable.menu_exit);
		bmpMenu_help=BitmapFactory.decodeResource(getResources(), R.drawable.menu_help);
		bmpMenu_menu=BitmapFactory.decodeResource(getResources(), R.drawable.menu_help);
		bmpMenu_play=BitmapFactory.decodeResource(getResources(), R.drawable.menu_play);
		bmpMenu_replay=BitmapFactory.decodeResource(getResources(), R.drawable.menu_replay);
		bmpMenu_resume=BitmapFactory.decodeResource(getResources(), R.drawable.menu_resume);
		bmpMenuBack=BitmapFactory.decodeResource(getResources(), R.drawable.menu_back);
		bmpWinbg=BitmapFactory.decodeResource(getResources(), R.drawable.gamewin);
		// TODO Auto-generated constructor stub
	}

	/* (non-Javadoc)
	 * @see android.view.SurfaceHolder.Callback#surfaceChanged(android.view.SurfaceHolder, int, int, int)
	 */
	@Override
	public void surfaceChanged(SurfaceHolder holder, int format, int width,
			int height) {
		// TODO Auto-generated method stub

	}

	/* (non-Javadoc)
	 * @see android.view.SurfaceHolder.Callback#surfaceCreated(android.view.SurfaceHolder)
	 */
	@Override
	//SurfaceView创建
	public void surfaceCreated(SurfaceHolder holder) {
		if (gameState==GANESTATE_MENU) {
			screenH=this.getHeight();
			screenW=this.getWidth();
			hbPlay = new HButton(bmpMenu_play, screenW / 2 - bmpMenu_help.getWidth() / 2, 150);
			hbHelp = new HButton(bmpMenu_help, hbPlay.getX(), hbPlay.getY() + 50);
			hbExit = new HButton(bmpMenu_exit, hbPlay.getX(), hbHelp.getY() + 50);
			hbBack = new HButton(bmpMenuBack, 0, screenH - bmpMenu_help.getHeight());
			hbResume = new HButton(bmpMenu_resume, screenW / 2 - bmpMenu_help.getWidth() / 2, 200);
			hbReplay = new HButton(bmpMenu_replay, hbResume.getX(), hbResume.getY() + 50);
			hbMenu = new HButton(bmpMenu_menu, hbResume.getX(), hbReplay.getY() + 50);
			world.setContactListener(this);
		}
		flag=true;
		th=new Thread(this);
		th.start();
	}

	/* (non-Javadoc)
	 * @see android.view.SurfaceHolder.Callback#surfaceDestroyed(android.view.SurfaceHolder)
	 */
	@Override
	public void surfaceDestroyed(SurfaceHolder holder) {
		// TODO Auto-generated method stub
		flag=false;
	}

	/* (non-Javadoc)
	 * @see java.lang.Runnable#run()
	 */
	@Override
	public void run() {
		while (flag) {
			//long start=System.currentTimeMillis();
			MyDraw();
			Lgoic();
			//long end=System.currentTimeMillis();
			try {
				Thread.sleep((long) timeStep * 1000);
				
			} catch (Exception e) {
				Log.e("Mihi", "Thread is Error!");
			}
		}
	}

	private void Lgoic() {
		switch (gameState) {
		case GANESTATE_MENU:			
			break;
		case GANESTATE_HELP:
			break;
		case GANESTATE_GAMEING:
			break;
		}
	}

	private void MyDraw() {
		canvas=sfh.lockCanvas();
		canvas.drawColor(Color.BLACK);
		try {
			switch (gameState) {
			case GANESTATE_MENU:
				canvas.drawBitmap(bmp_menubg, 0,0, paint);
				hbPlay.draw(canvas, paint);
				hbHelp.draw(canvas, paint);
				hbExit.draw(canvas, paint);
				break;
			case GANESTATE_HELP:
				break;
			case GANESTATE_GAMEING:
				break;
			}
			
		} catch (Exception e) {
			Log.e("Mihi", "Thread is Error!");
		}finally{
			if (canvas!=null) {
				sfh.unlockCanvasAndPost(canvas);
			}
			
		}
	}

	/**
	 * 在物理世界中添加矩形Body
	 * @param bmp
	 * @param x
	 * @param y
	 * @param w
	 * @param h
	 * @param density
	 * @return
	 */
	public Body createRect(Bitmap bmp,float x,float y,float w,float h,float density) {
		PolygonDef pd=new PolygonDef();
		pd.density=density;
		pd.friction=0.8f;
		pd.restitution=0.3f;
		pd.setAsBox(w/2/RATE, h/2/RATE);
		BodyDef bd=new BodyDef();
		bd.position.set((x+w/2)/RATE, (y+h/2)/RATE);
		Body body = world.createBody(bd);
		body.m_userData=new MyRect(bmp, x, y);
		body.createShape(pd);
		body.setMassFromShapes();
		return body;		
	}
	/**
	 * 在物理世界中添加圆形Body
	 * @param bmp
	 * @param x
	 * @param y
	 * @param r
	 * @param density
	 * @return
	 */
	public Body createCircle(Bitmap bmp,float x,float y,float r,float density) {
		CircleDef cd=new CircleDef();
		cd.density=density;
		cd.friction=0.8f;
		cd.restitution=0.3f;
		cd.radius=r/RATE;
		BodyDef bd=new BodyDef();
		bd.position.set((x+r)/RATE, (y+r)/RATE);
		Body body=world.createBody(bd);
		body.m_userData=new MyCircle(bmp, x, y, r);
		body.createShape(cd);
		body.setMassFromShapes();
		//放置小球进入休眠，导致改变重力方向，小球无法移动
		body.allowSleeping(false);
		return body;
		
	}
	@Override
	public void add(ContactPoint point) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void persist(ContactPoint point) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void remove(ContactPoint point) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void result(ContactResult point) {
		// TODO Auto-generated method stub
		
	}

}

[hairelove]

没有高手解惑呀，跪求解惑

[hairelove]

在详细说明下，如果在MySurfaceView中不实现接口ContactListener，就可以成功找到MySurfaceView类，但是实现ContactListener接口，又无法找到org.jbox2d.dynamics包，请高手解惑之