在 swift 中点击 tabBar 时如何显示不同的 ViewController

Question

我有三个 viewController，其中两个连接到 tabBarController。因此，当点击 tabBar 项 here is my storyboard

时，应用程序应该显示两个 vc 的依赖布尔值之一

import UIKit

class TabBarController: UITabBarController, UITabBarControllerDelegate {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
      
        
    }
    
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        let userLoggedIn: Bool!
        if tabBarController.selectedIndex == 1{
            if userLoggedIn == true{
                // show firstVC
            }else{
                // show secondVC
            }
        }
    }
}

Answer 1

您可以使用子ViewController，父ViewController来自Storyboard。

   override func viewDidLoad() {
        super.viewDidLoad()
        
       ///add two ChildVC here, hide 1 ifneeded
    }

单击此选项卡时，您会选中 userLoggedIn。

   override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        if userLoggedIn == true {
               /// show first childVC
               /// hide second childVC
         } else {
                /// hide first childVC
               /// show second childVC
         }
    }

您可以查看演示：Demo

Answer 2

只需在修改userLoggedIn变量时设置viewController列表即可（假设userLoggedIn为TabBarCOntroller实例变量）：

class TabBarC: UITabBarController {

    @IBOutlet var firstVC : FirstViewController!
    @IBOutlet var secondVC : SecondViewController!
    @IBOutlet var thirdVC : ThirdViewController!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        for vc in self.viewControllers! {
            if let fv = vc as? FirstViewController {
                firstVC = fv
            } else if let fv = vc as? SecondViewController  {
                secondVC = fv
            } else if let fv = vc as? ThirdViewController  {
                thirdVC = fv
            }
        }
    }


    var userLoggedIn : Bool = false {
        didSet {
        if userLoggedIn {
            self.viewControllers = [firstVC, thirdVC]
        } else {
            self.viewControllers = [secondVC, thirdVC]
        }
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self. userLoggedIn = false
    }

    override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
        if item.tag == 3 { // For purpose of test i set tag for 3 VC to 1 for firsttVC, 2 for secondVC, 3 for thirdVC
            // for test : change login value each time thirdVC is selected
            userLoggedIn = ! userLoggedIn
        }
    }

因此，每次在代码中的任何位置设置 userLoggedIn 时，选项卡都会显示所需的选项卡栏项目。 3 VC 被添加到 stpryboard 中的标签栏。选择第三VC时，第一个选项卡栏项目在一个和二

之间更改

Answer 3

只需像这样在 viewDidLoad 中将 .overCurrentContext 添加到 modalPresentationStyle。

 let newVC = self.storyboard?.instantiateViewController(withIdentifier:"secondVC")
 newVC?.modalPresentationStyle = .overCurrentContext
 self.present(newVC!, animated: false, completion: nil)

在 swift 中点击 tabBar 时如何显示不同的 ViewController

How to show different ViewControllers when tapping on tabBar in swift

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