NavigationItem的背景和title的属性

 //背景图片

    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"bar_bj.png"] forBarMetrics:UIBarMetricsDefault];

//navigationItem title的颜色

    NSDictionary *navTitleArr = [NSDictionary dictionaryWithObjectsAndKeys:[UIColor whiteColor],NSForegroundColorAttributeName,nil];

    self.navigationController.navigationBar.titleTextAttributes = navTitleArr;