ios NavigationController navigat

这样写就不会出现，切换页面导航栏黑条问题了

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:animated];

}
-(void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    [self.navigationController setNavigationBarHidden:NO animated:animated];

}