andengine一个方法的奇怪问题

[rczjp]

public void addSprite() {
final Scene mScene = MainActivity.this.mEngine.getScene();
Rectangle rectangle = new Rectangle(10, 10, 30, 30, mEngine.getVertexBufferObjectManager());
mScene.attachChild(rectangle);
}


public Scene onCreateScene() {
final Scene scene = new Scene();
addSprite();//这样的话就是错误的，为什么?
下面这样就正常，为什么？
Rectangle rectangle = new Rectangle(10, 10, 30, 30, mEngine.getVertexBufferObjectManager());
scene.attachChild(rectangle);
return scene;
}