我有以编程方式完成的Tabbar控制器。和选项卡栏工作正常。在stroyboard中，我创建了firstViewController并分配了类名firstViewController。当我尝试在标签栏控制器上的第一个vc标签上导航到第一个viewcontroller时，它崩溃了。如果我以编程方式给出，则表示效果很好。

如何从编程方式的选项卡栏控制器导航到情节提要视图控制器。

这是我的标签栏控制器代码：

 let tabBarCnt = UITabBarController()
 func createtabBarController() {

    let firstVC = FViewController()
    firstVC.tabBarItem = UITabBarItem(tabBarSystemItem: .search,tag: 0)

    let secondVC = SViewController()
    secondVC.tabBarItem = UITabBarItem(tabBarSystemItem: .more,tag: 1)

    let thirdVC = ViewController()
    thirdVC.tabBarItem = UITabBarItem(tabBarSystemItem: .history,tag: 2)

    let fourthVC = ViewController()
    fourthVC.tabBarItem = UITabBarItem(tabBarSystemItem: .downloads,tag: 3)


    if UIDevice.current.userInterfaceIdiom == .pad {
        let controllerArray = [firstVC,secondVC,thirdVC,fourthVC]
        tabBarCnt.viewControllers = controllerArray.map{ UINavigationController.init(rootViewController: $0)}

        self.view.addSubview(tabBarCnt.view)
    } else {
        let controllerArray = [firstVC,secondVC]
        tabBarCnt.viewControllers = controllerArray.map{ UINavigationController.init(rootViewController: $0)}

        self.view.addSubview(tabBarCnt.view)
    }

}

这是我的firstViewController代码的firstVC：

import UIKit

class FViewController: UIViewController,UITabBarDelegate {

@IBOutlet weak var firstBtn: UIButton!

@IBOutlet weak var fview: UIView!
override func viewDidLoad() {
    super.viewDidLoad()

    self.view.backgroundColor =  UIColor.blue
 // self.fview.backgroundColor = .brown


    // Do any additional setup after loading the view.
   }


}