無法看到控制器以編程方式添加到UITabBar swift

Question

我以故事板和一個UITabBarItem - 菜單以編程方式添加了2個tabBar項目。我成功地能夠打開與我使用storyboard創建的tabBarItems對應的控制器。然而，當我點擊「菜單」出現黑屏，

@objc public class MainScreenTabsController : UITabBarController { 
public override func viewDidLoad() { 
    super.viewDidLoad() 
    let tabController = MyViewController() 
    let tabBarItem = UITabBarItem(title: "Menu", image: UIImage(named: "more-options.png"), selectedImage: UIImage(named: "more-options")) 
    tabController.tabBarItem = tabBarItem 
    var array = self.viewControllers 
    array?.append(tabController) 
    self.viewControllers = array 
} 

public func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool { 
    return true; 
} 

public override func viewWillAppear(_ animated: Bool) { 
    super.viewWillAppear(animated) 
} 
} 

我跟着幾個教程添加標籤欄項目，但他們都有我寫的代碼。我錯過了一些非常基本的東西嗎？

編輯：

類的菜單控制

@objc public class MyViewController:UIViewController { 

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

public override func viewWillAppear(_ animated: Bool) { 
    super.viewWillAppear(animated) 
} 
} 

Answer 1

您的應用做什麼你的代碼是告訴它做的事。您正在創建MyViewController的實例並將其添加到UITabBarController的視圖控制器陣列中。

您的MyViewController類文件只是定義了一個空白的黑色視圖。

我猜你在Storyboard中創建了一個你想用作MyViewController的ViewController？如果是這樣，你需要從故事板實例化。

當你編輯的故事板，分配MyViewController類的VC要使用，並也給它一個Storyboard ID - 如MyVC。然後，編輯viewDidLoad功能如下：

public override func viewDidLoad() { 
    super.viewDidLoad() 

    // wrong way 
    // let tabController = MyViewController() 

    if let tabController = storyboard?.instantiateViewController(withIdentifier: "MyVC") as? MyViewController { 

     let tabBarItem = UITabBarItem(title: "Menu", image: UIImage(named: "more-options.png"), selectedImage: UIImage(named: "more-options")) 
     tabController.tabBarItem = tabBarItem 
     var array = self.viewControllers 
     array?.append(tabController) 
     self.viewControllers = array 

    } 

} 

Answer 2

既然你編程即創建視圖控制器。沒有nib/storyboard，你負責實例化一個UIView對象並設置視圖控制器的視圖屬性。要做到這一點，實現loadView方法並分配視圖對象來查看viewController的屬性。那麼你可以添加自定義視圖到視圖對象，檢查下面的代碼。

class MyViewController: UIViewController { 

    override func loadView() { 
     // super.loadView() // DO NOT CALL SUPER 

     //create view 
     view = UIView() 
     view.backgroundColor = UIColor.white 

     //Add a custom view with red color 
     let customView = UIView() 
     customView.translatesAutoresizingMaskIntoConstraints = false 
     customView.backgroundColor = UIColor.red 
     view.addSubview(customView) 

     NSLayoutConstraint.activate(
      [customView.leadingAnchor.constraint(equalTo: view.leadingAnchor), 
      customView.trailingAnchor.constraint(equalTo: view.trailingAnchor), 
      customView.topAnchor.constraint(equalTo: view.topAnchor), 
      customView.bottomAnchor.constraint(equalTo: view.bottomAnchor)] 
     ) 
    } 

    override func viewDidLoad() { 
     super.viewDidLoad() 

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

這將是很好的使用情節提要/筆尖爲了這個目的，你可以輕鬆地配置使用界面生成器的自動佈局，而不是編程方式做自定義視圖/控制。 :)

編輯：

如果傻冒用故事板則實例化視圖控制器如下面的代碼給出

class MainScreenTabsController: UITabBarController, UITabBarControllerDelegate { 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     // Do any additional setup after loading the view. 
     let tabController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "MainViewController") as! MainViewController //if using storyboard 
     let icon = UITabBarItem(title: "Menu", UIImage(named: "more-options.png"), selectedImage: UIImage(named: "more-options"))) 
     tabController.tabBarItem = icon 
     var controllers = self.viewControllers 
     controllers?.append(tabController) 
     self.setViewControllers(controllers!, animated: true) 
    } 
}