完美解决nav隐藏

- (void)viewWillAppear:(BOOL)animated

{

    [self.navigationController setNavigationBarHidden:YES animated:YES];

    [superviewWillAppear:animated];

}

- (void)viewWillDisappear:(BOOL)animated

{

    [self.navigationController setNavigationBarHidden:NO animated:YES];

    [super viewWillDisappear:animated];

}