导航navigationItem

UINavigationItem有以下属性影响着导航栏的内容
左上角的返回按钮

@property(nonatomic,retain) UIBarButtonItem *backBarButtonItem;

中间的标题视图

@property(nonatomic,retain) UIView  *titleView;

中间的标题文字

@property(nonatomic,copy)   NSString  *title;

左上角的视图

@property(nonatomic,retain) UIBarButtonItem *leftBarButtonItem;

UIBarButtonItem *rightBarButtonItem  右上角的视图

@property(nonatomic,retain) UIBarButtonItem *rightBarButtonItem;