cocos2d-Android游戏开发，场景的切换

请看下面的代码，我从start场景切换到main场景时，为什么main场景里的动画实现不了啊，求大虾帮帮忙，谢谢！

package com.example.leidiandazhan;

import org.cocos2d.layers.CCScene;

import org.cocos2d.nodes.CCDirector;
import org.cocos2d.opengl.CCGLSurfaceView;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;

public class MainActivity extends Activity {
private CCGLSurfaceView view;
private CCDirector director = CCDirector.sharedDirector();
private CCScene scene = CCScene.node();

private StartLayer start;
private MainLayer main;
private EndLayer end;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    this.getWindow().setFlags(
            WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
            WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

    view = new CCGLSurfaceView(this);
    setContentView(view);

    director.attachInView(view);
    director.setScreenSize(320, 480);
    director.setDisplayFPS(true);
    director.setAnimationInterval(1 / 30);

    start = new StartLayer(this);
    scene.addChild(start);
    director.runWithScene(scene);
}

public void toMainLayer() {     
    main = new MainLayer(this);
    scene.addChild(main);
    director.replaceScene(scene);
    start.removeAllChildren(true);
}

public void toEndLayer() {
    end = new EndLayer(this);
    scene.addChild(end);
    director.replaceScene(scene);
}

}