使用UITabBarController的持久视图

Question

我正在尝试构建一个类似于Apple Music的应用程序 - 带有持久视图的标签栏导航，可从应用程序的任何位置访问。视图可以扩展为占据整个屏幕或最小化，静态高度为80. UI构建在具有正常UITabBarController的故事板中。这是初稿：

这就是我构建它的方式：

class TabbarViewController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        embedLiveFeedbackController()
    }

    private func embedLiveFeedbackController() {
        guard let feedbackController = UIStoryboard(name: "LiveFeedback", bundle: nil).instantiateInitialViewController() as? LiveFeedbackViewController else { return }

        feedbackController.stateDelegate = self
        addChildViewController(feedbackController)
        view.addSubview(feedbackController.view)

        feedbackController.view.translatesAutoresizingMaskIntoConstraints = false
        feedbackController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        feedbackController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        feedbackController.view.bottomAnchor.constraint(equalTo: tabBar.topAnchor).isActive = true

        liveFeedbackTopConstraint = feedbackController.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor)
        liveFeedbackHeightConstraint = feedbackController.view.heightAnchor.constraint(equalToConstant: Constants.minimizedHeight)

        liveFeedbackHeightConstraint?.isActive = true
        liveFeedbackTopConstraint?.isActive = false

    }
}

我遇到的问题是视图控制器的内容落后于持久视图，并且不完全可见。我尝试过的一件事就是将视图控制器限制在持久视图的顶部：

private func constraintViewControllers() {
    guard let vcs = viewControllers else { return }
    guard let topAnchor = liveFeedbackTopAnchor else { return } // a reference to the top anchor of the persistent view

    for viewController in vcs {
        viewController.view.translatesAutoresizingMaskIntoConstraints = false
        viewController.view.bottomAnchor.constraint(equalTo: topAnchor).isActive = true
    }
}

当然，我收到以下错误：

Unable to activate constraint with anchors <NSLayoutYAxisAnchor:0x600000864640 "UILayoutContainerView:0x7fc813f0ea60.bottom"> and <NSLayoutYAxisAnchor:0x60400047b980 "UIView:0x7fc813f08af0.bottom"> because they have no common ancestor.  Does the constraint or its anchors reference items in different view hierarchies?  That's illegal.'

有关如何实施此建议的任何建议吗？

Answer 1

这是我的建议，我测试过，效果很好

创建一个主 viewController 并在其中放置 2 个视图（如图所示）：

-startViewController 
--containerView (your app root viewController/tabBarController goes here)
--persistentView

在 startViewController

class ViewController: UIViewController {

var tabController : TabController!

@IBOutlet weak var containerView: UIView!
@IBOutlet weak var persistentView: UIView!
@IBOutlet weak var persistentBottomConstraint: NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()
    
    tabController = TabController.initFromStoryBord()
    
    self.addChild(tabController)
    tabController.view.frame = containerView.bounds
    containerView.addSubview(tabController.view)
    tabController.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]
    
   
    persistantBottomConstraint.constant = tabController.tabBar.frame.height
}
}

然后是 TabBarController 的类：

确保为 tabController 设置 Stroyboard ID

class TabController : UITabBarController {
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    static func initFromStoryBord() -> TabController {
        let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "TabController") as! TabController
        return vc
    }
}