title: trouble occurred When I pushViewController
body: <p>Recently, a strange question occurred when I pushViewController to the next viewController.
  Why I think it's a strange question? because it don't always appears(The probability of occurrence is low). when it appears, next viewController only shows its nav bar on screen, I still can see the rootViewController, but touching it without reaction(PopGesture is effective).Hoping for your help, thanks very much.</p>
  
  <p><a href="https://i.stack.imgur.com/s6fnl.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/s6fnl.jpg" alt="enter image description here"></a></p>
  
  <pre><code>#pragram mark - method of pushing   
  - (void)clickToAccout {
  
      if (![self countTotalSelectedNumber]) {
          [SVProgressHUD showInfoWithStatus:@"没有被选择的商品"];
          return;
      }
  
      CSCreatOrderViewController *creatOrderVC = [[CSCreatOrderViewController alloc] init];
      creatOrderVC.totalPrice = [self countTotalPrice];
      creatOrderVC.goods = [self selectedGoods];
  
      [self.navigationController pushViewController:creatOrderVC animated:YES];
  }
  
  #pragma mark - chlid class of navgationController
  
  - (void)viewDidLoad {
      [super viewDidLoad];
  
      self.navigationBar.tintColor = [UIColor whiteColor];
  }
  
  - (UIStatusBarStyle)preferredStatusBarStyle {
      return _barStyle;
  }
  
  - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated{
      if (self.viewControllers.count &gt; 0) {
          viewController.hidesBottomBarWhenPushed = YES;
          [SVProgressHUD dismiss];
      }
  
      [super pushViewController:viewController animated:animated];
  }
  
  - (UIViewController *)popViewControllerAnimated:(BOOL)animated {
      [SVProgressHUD dismiss];
  
      return [super popViewControllerAnimated:animated];
  }
  
  - (void)didReceiveMemoryWarning {
      [super didReceiveMemoryWarning];
      // Dispose of any resources that can be recreated.
  }
  
  
  #pragma mark - tabBarController
  
  - (void)viewDidLoad {
      [super viewDidLoad];
  
      CSTabBar *tabBar = [[CSTabBar alloc] init];
      [self setValue:tabBar forKey:@"tabBar"];
  
      [self.tabBar setTintColor:[UIColor cz_colorWithHex:0Xec5151]];
  
      [self addChildViewControllerWithTitle:@"首页" imageName:@"home" controllerName:@"CSHomeViewController"];
      [self addChildViewControllerWithTitle:@"分类" imageName:@"classify" controllerName:@"CSClassifyViewController"];
      [self addChildViewControllerWithTitle:@"查询" imageName:@"search" controllerName:@"CSSearchViewController"];
      [self addChildViewControllerWithTitle:@"购物车" imageName:@"cart" controllerName:@"CSShoppingCartViewController"];
      [self addChildViewControllerWithTitle:@"我的" imageName:@"mine" controllerName:@"CSMineViewController"];
  
      self.selectedIndex = 0;
  }
  
  - (void)addChildViewControllerWithTitle:(NSString *)title imageName:(NSString *)imageName controllerName:(NSString *)controllerName {
  
      Class cls = NSClassFromString(controllerName);
  
      UIViewController *vc = [[cls alloc] init];
      vc.title = title;
      [vc.tabBarItem setImage:[UIImage imageNamed:[NSString stringWithFormat:@"%@",imageName]]];
      [vc.tabBarItem setSelectedImage:[UIImage imageNamed:[NSString stringWithFormat:@"%@_selected",imageName]]];
      vc.tabBarItem.title = title;
  
      CSNavigationController *nav = [[CSNavigationController alloc] initWithRootViewController:vc];
      [self addChildViewController:nav];
  }
  
  
  #pragma mark - base viewController
  - (void)viewDidLoad {
      [super viewDidLoad];
  
      self.view.backgroundColor = [UIColor whiteColor];
  
      [self setupNavItem];
  
      self.navigationController.interactivePopGestureRecognizer.enabled = YES;
      self.navigationController.interactivePopGestureRecognizer.delegate = self;
  
      _indciatorView = [[CSIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
  
      UIWindow *keyW = [UIApplication sharedApplication].keyWindow;
      [keyW addSubview:_indciatorView];
  
      [_indciatorView mas_makeConstraints:^(MASConstraintMaker *make) {
          make.center.equalTo(keyW);
      }];
  }
  
  
  - (void)setupNavItem {
  
      UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
      button.imageEdgeInsets = UIEdgeInsetsMake(9, 0, 9, 29);
      [button setImage:[UIImage imageNamed:@"left"] forState:UIControlStateNormal];
      [button addTarget:self action:@selector(clickToDismiss) forControlEvents:UIControlEventTouchUpInside];
  
      self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button];
  }
  
  - (void)clickToDismiss {
      [self.navigationController popViewControllerAnimated:YES];
  }
  
  - (void)didReceiveMemoryWarning {
      [super didReceiveMemoryWarning];
  }
  </code></pre>