MDCTabBarViewController获取条至最高位置

Question

我在我的应用程序中使用iOS Material组件，但遇到标签here。实施起来很容易，在我做了一些小的改动以匹配我的设计之后，结果就是我想要的：

我使用以下代码实现了这一点：

func setupTabBar() {
    let customTabBar = MDCTabBar(frame: view.bounds)
    customTabBar.items = [
        UITabBarItem(title: "Cards", image: nil, tag: 0),
        UITabBarItem(title: "Mobile", image: nil, tag: 0)            
    ]
    customTabBar.itemAppearance = .titledImages
    customTabBar.alignment = .justified
    customTabBar.itemAppearance = .titles

    //colors
    customTabBar.tintColor = #colorLiteral(red: 0.8039215803, green: 0.8039215803, blue: 0.8039215803, alpha: 1)
    customTabBar.selectedItemTintColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
    customTabBar.unselectedItemTintColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
    customTabBar.barTintColor = UIColor(red:0.00, green:0.33, blue:0.59, alpha:1.0)

    tabBarContainerView.addSubview(customTabBar)
    customTabBar.sizeToFit()

    tabBarContainerView.layer.shadowOffset = CGSize(width: 0, height: 2)
    tabBarContainerView.layer.shadowRadius = 8
    tabBarContainerView.layer.shadowOpacity = 0.5
    tabBarContainerView.layer.shadowColor = UIColor.black.cgColor        
}

但是，这只是Tar栏，我需要有一个功能性的标签视图，用户可以在其中切换两个页面。没问题，正如文档所说的那样，它们仅继承自MDCTabBarViewController，这确保了我的页面被制表，但是这还在底部添加了另一个选项卡栏，这很好，现在我不能自己创建一个，所以我删除了我的，现在我只希望它排在最前面，但是找不到要设置为使其位于顶部的属性：

这是该代码：

func setupTabViews()  {
    let storyboard = UIStoryboard.init(name: "Main", bundle: nil)
    let cardsVC = storyboard.instantiateViewController(withIdentifier: "cardsWalletViewController")
    let mobileVC = storyboard.instantiateViewController(withIdentifier: "mobileWalletViewController")

    let vcArray = [cardsVC, mobileVC]
    viewControllers = vcArray

    let childVC = viewControllers.first
    selectedViewController = childVC

    tabBar?.delegate = self

    tabBar?.items = [
        UITabBarItem(title: "Cards", image: nil, tag: 0),
        UITabBarItem(title: "Mobile", image: nil, tag: 0)
    ]

    tabBar?.itemAppearance = .titledImages
    tabBar?.alignment = .justified
    tabBar?.itemAppearance = .titles

    //colors
    tabBar?.tintColor = #colorLiteral(red: 0.8039215803, green: 0.8039215803, blue: 0.8039215803, alpha: 1)
    tabBar?.selectedItemTintColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
    tabBar?.unselectedItemTintColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
    tabBar?.barTintColor = UIColor(red:0.00, green:0.33, blue:0.59, alpha:1.0)

    tabBar?.selectedItem = tabBar?.items.first
}

我注意到在MDCTabBarViewController的文档中，它将创建一个底部锚定的标签栏，但是如何以它们在“标签”组件示例中清楚地说明的方式使用它，标签位于顶部？ / p>