ios - 在 iOS 上使用 MDCBottomNavigationBar 切换 View Controller

Question

我正在尝试创建一个使用 Material Design 库底部导航功能的 iOS 应用程序。我可以获得一个带有底部导航栏的 View Controller 来编译和显示，但是我无法添加其他 View Controller 并在单击不同选项卡时在它们之间切换。我将所有内容简化为两个文件:一个是带有底部导航内容的入口 View Controller ，另一个只是一个非常简单的 View Controller ，我实例化了 3 次以用作三个选项卡的目标。

目前，我的具体错误是:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'headerViewController does not have a parentViewController. Use [self addChildViewController:appBar.headerViewController]. This warning only appears in DEBUG builds'

据我所知，这与我的选项卡 View 有关。如果我注释掉执行 self.viewControllers = [...] 的行，那么它将正常加载，但不会在 View Controller 之间切换。

我不喜欢这种方法。如果有另一种方法可以做到这一点，我很想知道。我无法从文档中学到很多东西，但如果有其他类似选项卡的 Material Design 功能的文档，它们的工作方式非常相似，我认为这将为我指明正确的方向。

这是我的入口 View Controller 。我以其中一个示例为基础并对其进行了大量修改。

    import Foundation
import MaterialComponents
import UIKit

class ICEBottomNavController: UITabBarController, MDCBottomNavigationBarDelegate
{
    let appBar = MDCAppBar()
    var colorScheme = MDCSemanticColorScheme()

    // Create a bottom navigation bar to add to a view.
    let bottomNavBar = MDCBottomNavigationBar()

    init()
    {
        super.init(nibName: nil, bundle: nil)
        initCommon()
    }

    @available(*, unavailable)
    required init?(coder aDecoder: NSCoder)
    {
        super.init(coder: aDecoder)
        initCommon()
    }

    func initCommon()
    {
        self.title = "Bottom Navigation (Swift)"

        let statusVC = ICEChildBottomBarViewController( title: "Status", color: UIColor.orange )
        let eventsVC = ICEChildBottomBarViewController( title: "Events", color: UIColor.blue )
        let contactsVC = ICEChildBottomBarViewController( title: "Contacts", color: UIColor.cyan )

        self.viewControllers = [ statusVC, eventsVC, contactsVC ]

        self.addChildViewController( appBar.headerViewController )
        let color = UIColor(white: 0.2, alpha:1)
        appBar.headerViewController.headerView.backgroundColor = color
        appBar.navigationBar.tintColor = .white
        appBar.navigationBar.titleTextAttributes = [NSAttributedStringKey.foregroundColor : UIColor.white]

        //appBar.headerViewController.viewControllers

        commonBottomNavigationTypicalUseSwiftExampleInit()
    }

    func bottomNavigationBar(_ bottomNavigationBar: MDCBottomNavigationBar, didSelect item: UITabBarItem)
    {
        print( "did select item \(item.tag)" )

        self.selectedIndex = item.tag

        //self.viewControllers?[item.tag].addChildViewController( appBar.headerViewController )
        //self.selectedViewController = self.viewControllers?[item.tag]

//      self.viewControllers
    }

    func commonBottomNavigationTypicalUseSwiftExampleInit()
    {
        view.backgroundColor = .lightGray
        view.addSubview(bottomNavBar)

        // Always show bottom navigation bar item titles.
        bottomNavBar.titleVisibility = .always

        // Cluster and center the bottom navigation bar items.
        bottomNavBar.alignment = .centered

        // Add items to the bottom navigation bar.
        let tabBarItem1 = UITabBarItem( title: "Status",   image: nil, tag: 0 )
        let tabBarItem2 = UITabBarItem( title: "Events",   image: nil, tag: 1 )
        let tabBarItem3 = UITabBarItem( title: "Contacts", image: nil, tag: 2 )
        bottomNavBar.items = [ tabBarItem1, tabBarItem2, tabBarItem3 ]

        // Select a bottom navigation bar item.
        bottomNavBar.selectedItem = tabBarItem1;
        bottomNavBar.delegate = self
    }

    func layoutBottomNavBar()
    {
        let size = bottomNavBar.sizeThatFits(view.bounds.size)
        let bottomNavBarFrame = CGRect( x: 0,
                                        y: view.bounds.height - size.height,
                                        width: size.width,
                                        height: size.height )
        bottomNavBar.frame = bottomNavBarFrame
    }

    override func viewWillLayoutSubviews()
    {
        super.viewWillLayoutSubviews()
        layoutBottomNavBar()
    }

    #if swift(>=3.2)
    @available(iOS 11, *)
    override func viewSafeAreaInsetsDidChange()
    {
        super.viewSafeAreaInsetsDidChange()
        layoutBottomNavBar()
    }
    #endif

    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.selectedIndex = 0


        appBar.addSubviewsToParent()

        // Theme the bottom navigation bar.
        MDCBottomNavigationBarColorThemer.applySemanticColorScheme(colorScheme, toBottomNavigation: bottomNavBar);

    }

    override func viewWillAppear(_ animated: Bool)
    {
        super.viewWillAppear(animated)
        self.navigationController?.setNavigationBarHidden( true, animated: animated )
    }
}

// MARK: Catalog by convention
extension ICEBottomNavController
{
    class func catalogBreadcrumbs() -> [String] {
        return ["Bottom Navigation", "Bottom Navigation (Swift)"]
    }

    class func catalogIsPrimaryDemo() -> Bool {
        return false
    }

    func catalogShouldHideNavigation() -> Bool {
        return true
    }
}

我的简单 View Controller 应该被选项卡切换:

import Foundation
import MaterialComponents
import UIKit

class ICEChildBottomBarViewController: UIViewController
{
    //let appBar = MDCAppBar()
    //var colorScheme = MDCSemanticColorScheme()
    var color: UIColor?

    init( title: String, color: UIColor )
    {
        super.init(nibName: nil, bundle: nil)
        self.title = title
        self.color = color
    }

    @available(*, unavailable)
    required init?(coder aDecoder: NSCoder)
    {
        super.init(coder: aDecoder)
    }

    override func viewDidLoad()
    {
        super.viewDidLoad()

        view.backgroundColor = self.color

        //appBar.addSubviewsToParent()
    }

    override func viewWillAppear(_ animated: Bool)
    {
        super.viewWillAppear(animated)
        self.navigationController?.setNavigationBarHidden( true, animated: animated )
    }
}

Answer 1

你可以用这个来切换 Controller ，主要代码

class MaterialTabBarSimple: UITabBarController {
    let bottomNavBar = MDCBottomNavigationBar()
    // other code copy from Material doc
    override func viewDidLoad() {
       bottomNavBar = [ your tabBarItems ]
       bottomNavBar.delegate = self

       self.viewControllers = [ your controllers ]
    }
}
extension MaterialTabBarSimple: MDCBottomNavigationBarDelegate {
    func bottomNavigationBar(_ bottomNavigationBar: MDCBottomNavigationBar, didSelect item: UITabBarItem) {
        print("did select item \(item.tag)")
        self.selectedViewController = self.viewControllers![item.tag]
    }
}