问题与此问题类似。tabBarController didSelect does not get called

optional func tabBarController(_ tabBarController: UITabBarController, 
                     didSelect viewController: UIViewController)

在iOS v3.0及更高版本中，无论选定的视图控制器是否更改，选项卡栏控制器都会调用此方法。此外，仅在响应用户点击选项卡栏时才调用此方法，并且在代码以编程方式更改选项卡栏内容时不调用此方法。

在viewDidLoad中添加以下内容：

self.delegate = self

将其复制到代码中

class HomeTabBarVC: UITabBarController {

    var isIpad = false
    let button = UIButton.init(type: .custom)
    var index = 0
    override func viewDidLoad() {
        super.viewDidLoad()

        self.delegate = self

        APPDELEGATE.tabBar = self 

    }

}

extension HomeTabBarVC : UITabBarControllerDelegate {
    override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
        print("the last selected index is : \(selectedIndex)")
        APPDELEGATE.tabBarLastSelectedIndex = selectedIndex 
        print("the current selected index is : \(String(describing: tabBar.items?.index(of: item)))")
        APPDELEGATE.tabBarCurrentSelectedIndex = tabBar.items?.index(of: item) ?? 0
        }

   }

在appdelegate中声明此变量，

var tabBar : UITabBarController?