在另一个视图控制器中添加视图控制器作为子视图 [英] Adding a view controller as a subview in another view controller

问题描述

我找到了这个问题的帖子，但没有一个帖子解决了我的问题。

说得像我一样..

1. ViewControllerA


2. ViewControllerB

I试图在ViewControllerA中添加ViewControllerB作为子视图但是，它会抛出类似致命错误：在展开可选值时意外发现nil 的错误。

以下是代码......

ViewControllerA

  var testVC：ViewControllerB = ViewControllerB（）; 
 
覆盖func viewDidLoad（）
 {
 super.viewDidLoad（）
 self.testVC.view.frame = CGRectMake（0,0,350,450）; 
 self.view.addSubview（testVC.view）; 
 //加载视图后进行任何其他设置。 
} 
  

ViewControllerB只是一个带有标签的简单屏幕。

ViewControllerB

  @IBOutlet弱变测试：UILabel ！ 
 
覆盖func viewDidLoad（）{
 super.viewDidLoad（）
 test.text =成功//在这里抛出错误致命错误：在打开一个可选项时意外发现nil价值
} 
  

编辑

使用来自用户答案的​​建议解决方案，ViewControllerA中的ViewControllerB将离开屏幕。灰色边框是我为子视图创建的框架。

解决方案

一些观察结果：

1. 当你实例化第二个视图控制器时，你正在调用 ViewControllerB（）。如果该视图控制器以编程方式创建其视图（这是不寻常的），那将是好的。但是 IBOutlet 的存在表明第二个视图控制器的场景是在Interface Builder中定义的，但通过调用 ViewControllerB（），你没有给故事板一个机会来实例化那个场景并连接所有的插座。因此，隐式展开的 UILabel 为 nil ，从而导致出现错误消息。

   
   
   

   相反，您希望在Interface Builder中为目标视图控制器提供故事板ID，然后您可以使用 instantiateViewController（withIdentifier：）来实例化它（并连接所有IB网点）。在Swift 3中：

    让controller = storyboard！.instantiateViewController（withIdentifier：scene storyboard id）
     

   您现在可以访问此控制器的查看。




2. 但如果你真的想做 addSubview （即你没有过渡到下一个场景），那么你正在进行一种名为视图控制器遏制的练习。您不只想简单地 addSubview 。你想做一些额外的容器视图控制器调用，例如：

    让controller = storyboard.instantiateViewController（withIdentifier：scene storyboard id ）
    addChildViewController（controller）
    controller.view.frame = ... //或者更好，关闭`translatesAutoresizingMaskIntoConstraints`，然后为这个子视图定义约束
    view.addSubview（controller。查看）
    controller.didMove（toParentViewController：self）
     

   有关此原因的详细信息<需要code> addChildViewController 和 didMove（toParentViewController：），请参阅。

   
   

   I have found few posts for this problem but none of them solved my issue.

   Say like I've..

   1. ViewControllerA
   2. ViewControllerB

   I tried to add ViewControllerB as a subview in ViewControllerA but, it's throwing an error like "fatal error: unexpectedly found nil while unwrapping an Optional value".

   Below is the code...

   ViewControllerA

   var testVC: ViewControllerB = ViewControllerB();
   
   override func viewDidLoad()
   {
       super.viewDidLoad()
       self.testVC.view.frame = CGRectMake(0, 0, 350, 450);
       self.view.addSubview(testVC.view);
       // Do any additional setup after loading the view.
   }
   

   ViewControllerB is just a simple screen with a label in it.

   ViewControllerB

    @IBOutlet weak var test: UILabel!
   
   override func viewDidLoad() {
       super.viewDidLoad()
       test.text = "Success" // Throws ERROR here "fatal error: unexpectedly found nil while unwrapping an Optional value"
   }
   

   EDIT

   With the suggested solution from the user answers, ViewControllerB in ViewControllerA is going off the screen. Grey border is the frame I have created for the subview.

   解决方案

   A couple of observations:

   1. When you instantiate the second view controller, you are calling ViewControllerB(). If that view controller programmatically creates its view (which is unusual) that would be fine. But the presence of the IBOutlet suggests that this second view controller's scene was defined in Interface Builder, but by calling ViewControllerB(), you are not giving the storyboard a chance to instantiate that scene and hook up all the outlets. Thus the implicitly unwrapped UILabel is nil, resulting in your error message.

      Instead, you want to give your destination view controller a "storyboard id" in Interface Builder and then you can use instantiateViewController(withIdentifier:) to instantiate it (and hook up all of the IB outlets). In Swift 3:

      let controller = storyboard!.instantiateViewController(withIdentifier: "scene storyboard id")
      

      You can now access this controller's view.

   2. But if you really want to do addSubview (i.e. you're not transitioning to the next scene), then you are engaging in a practice called "view controller containment". You do not just want to simply addSubview. You want to do some additional container view controller calls, e.g.:

      let controller = storyboard.instantiateViewController(withIdentifier: "scene storyboard id")
      addChildViewController(controller)
      controller.view.frame = ...  // or better, turn off `translatesAutoresizingMaskIntoConstraints` and then define constraints for this subview
      view.addSubview(controller.view)
      controller.didMove(toParentViewController: self)
      

      For more information about why this addChildViewController and didMove(toParentViewController:) are necessary, see WWDC 2011 video #102 - Implementing UIViewController Containment. In short, you need to ensure that your view controller hierarchy stays in sync with your view hierarchy, and these calls to addChildViewController and didMove(toParentViewController:) ensure this is the case.

      Also see Creating Custom Container View Controllers in the View Controller Programming Guide.

   ---

   By the way, the above illustrates how to do this programmatically. It is actually much easier if you use the "container view" in Interface Builder.

   Then you don't have to worry about any of these containment-related calls, and Interface Builder will take care of it for you.

   For Swift 2 implementation, see previous revision of this answer.

   这篇关于在另一个视图控制器中添加视图控制器作为子视图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！