解决导航栏消失问题

- （voidviewWillapper:(Bool)animated{
    
    [super viewWillAppear:animated];
    self.navigationController.navigationBarHidden   = YES;
}

-(void)viewWillDisappear:(BOOL)animated{

      [super viewWillDisappear:animated];    self.navigationController.navigationBarHidden = NO;
}