初步学习andengine的问题

[mozpp]

package com.example.moz.myapplication;

import java.io.IOException;
import java.io.InputStream;

import org.andengine.engine.camera.Camera;
import org.andengine.engine.options.EngineOptions;
import org.andengine.engine.options.ScreenOrientation;
import org.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
import org.andengine.entity.scene.Scene;
import org.andengine.entity.scene.background.Background;
import org.andengine.entity.sprite.Sprite;
import org.andengine.entity.util.FPSLogger;
import org.andengine.opengl.texture.ITexture;
import org.andengine.opengl.texture.bitmap.BitmapTexture;
import org.andengine.opengl.texture.region.ITextureRegion;
import org.andengine.opengl.texture.region.TextureRegionFactory;
import org.andengine.ui.activity.SimpleBaseGameActivity;
import org.andengine.util.adt.io.in.IInputStreamOpener;
import org.andengine.util.debug.Debug;

public class MainActivity extends SimpleBaseGameActivity {

    private static final int CAMERA_WIDTH = 720;
    private static final int CAMERA_HEIGHT = 480;

    private ITexture mTexture;
    private ITextureRegion mFaceTextureRegion;

    @Override
    public EngineOptions onCreateEngineOptions() {
        final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);

        return new EngineOptions(true, ScreenOrientation.LANDSCAPE_SENSOR, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera);
    }

    @Override
    public void onCreateResources() {
        try {
            this.mTexture = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener() {
                @Override
                public InputStream open() throws IOException {
                    return getAssets().open("gfx/green.png");
                }
            });

            this.mTexture.load();
            this.mFaceTextureRegion = TextureRegionFactory.extractFromTexture(this.mTexture);
        } catch (IOException e) {
            Debug.e(e);
        }
    }

    @Override
    public Scene onCreateScene() {
        this.mEngine.registerUpdateHandler(new FPSLogger());

        final Scene scene = new Scene();
        scene.setBackground(new Background(0.09804f, 0.6274f, 0.8784f));

        /* Calculate the coordinates for the face, so its centered on the camera. */
        final float centerX = (CAMERA_WIDTH - this.mFaceTextureRegion.getWidth()) / 2;
        final float centerY = (CAMERA_HEIGHT - this.mFaceTextureRegion.getHeight()) / 2;

        /* Create the face and add it to the scene. */
        final Sprite face = new Sprite(centerX, centerY, this.mFaceTextureRegion, this.getVertexBufferObjectManager());
        scene.attachChild(face);

        return scene;
    }

}

这是我在网上复的代码，activity的，编译没问题，虚拟机和真机运行后黑屏了，求救！！！！！！！！！！！！！！！！！！！！！！！！！！！

[mozpp]

03-29 21:56:44.216 11572-11572/com.example.moz.myapplication E/﹕ Can't open file for reading 03-29 21:56:44.246 11572-11572/com.example.moz.myapplication E/﹕ Can't open file for reading 03-29 21:56:44.246 11572-11572/com.example.moz.myapplication E/﹕ Can't open file for reading 03-29 21:56:44.306 11572-11589/com.example.moz.myapplication E/AndEngine﹕ AndEngine java.io.FileNotFoundException: gfx/green.png at android.content.res.AssetManager.openAsset(Native Method) at android.content.res.AssetManager.open(AssetManager.java:316) at android.content.res.AssetManager.open(AssetManager.java:290) at com.example.moz.myapplication.MainActivity$1.open(MainActivity.java:43) at org.andengine.opengl.texture.bitmap.BitmapTexture.<init>(BitmapTexture.java:74) at org.andengine.opengl.texture.bitmap.BitmapTexture.<init>(BitmapTexture.java:48) at com.example.moz.myapplication.MainActivity.onCreateResources(MainActivity.java:40) at org.andengine.ui.activity.SimpleBaseGameActivity.onCreateResources(SimpleBaseGameActivity.java:41) at org.andengine.ui.activity.BaseGameActivity.onCreateGame(BaseGameActivity.java:181) at org.andengine.ui.activity.BaseGameActivity.onSurfaceCreated(BaseGameActivity.java:110) at org.andengine.opengl.view.EngineRenderer.onSurfaceCreated(EngineRenderer.java:80) at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1446) at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1216) 03-29 21:56:44.326 11572-11589/com.example.moz.myapplication E/AndEngine﹕ MainActivity.onCreateScene failed. @(Thread: 'GLThread 867') java.lang.NullPointerException at com.example.moz.myapplication.MainActivity.onCreateScene(MainActivity.java:62) at org.andengine.ui.activity.SimpleBaseGameActivity.onCreateScene(SimpleBaseGameActivity.java:48) at org.andengine.ui.activity.BaseGameActivity$3.onCreateResourcesFinished(BaseGameActivity.java:169) at org.andengine.ui.activity.SimpleBaseGameActivity.onCreateResources(SimpleBaseGameActivity.java:43) at org.andengine.ui.activity.BaseGameActivity.onCreateGame(BaseGameActivity.java:181) at org.andengine.ui.activity.BaseGameActivity.onSurfaceCreated(BaseGameActivity.java:110) at org.andengine.opengl.view.EngineRenderer.onSurfaceCreated(EngineRenderer.java:80) at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1446) at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1216)