在ios内接导航控件出问题，ui不刷新

Creator 2.x
#1

要内接一个web页面。增加web返回关闭按钮，使用了UINavigationController。

// Use RootViewController to manage CCEAGLView
_viewController = [[RootViewController alloc]init];
_viewController.wantsFullScreenLayout = YES;
_nav = [[UINavigationController alloc] init];
[_nav setNavigationBarHidden:YES];

// Set RootViewController to window
if ( [[UIDevice currentDevice].systemVersion floatValue] < 6.0)
{
    // warning: addSubView doesn't work on iOS6
    [window addSubview: _nav.view];
}
else
{
    // use this method on ios6
    [window setRootViewController:_nav];
}

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.rootViewController = _nav;
[self.window makeKeyAndVisible];

cocos2d::GLView *glview = cocos2d::GLViewImpl::createWithEAGLView((__bridge void *)_viewController.view);
cocos2d::Director::getInstance()->setOpenGLView(glview);

[_nav pushViewController:_viewController animated:YES];

加载过程如上面一样。

能正常启动，但是只要一按home键，再回来，ui就不刷新了，这个是什么问题啊，有人遇到过么。