从其子 UIViewControllers 访问父 UIViewController答案

【问题标题】：Accessing a parent UIViewController from its children UIViewControllers从其子 UIViewControllers 访问父 UIViewController
【发布时间】：2015-02-09 16:20:10
【问题描述】：

我有一个名为Container 的UIViewController，里面有另外两个孩子UIViewControllers：Master 和Detail。

我的问题是尝试从其子控制器之一访问Container。

应用代理代码：

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    var container: Container?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        window = UIWindow(frame: UIScreen.mainScreen().bounds)
        container = Container(nibName: "Container", bundle: nil)
        window?.rootViewController = Container()
        window?.makeKeyAndVisible()
        return true
    }

    func appShowDetailView(vc:UIViewController){
        container!.showDetailView(vc)
    }
}

容器代码：

import UIKit

class Container: UIViewController {

    var masterView:UIViewController?
    var detailView:UIViewController?
    var masterViewFrame = CGRectMake(0, 0, 0, 0)
    var detailViewFrame = CGRectMake(0, 0, 0, 0)
    var detailOnScreenFrame = CGRectMake(0, 0, 0, 0)
    var detailOffScreenFrame = CGRectMake(0, 0, 0, 0)
    var masterViewHeight:CGFloat = 50

    override func viewDidLoad() {
        super.viewDidLoad()
        masterView = MenuViewController(nibName: "MenuViewController", bundle: nil)
        detailView = RootViewController(nibName: "RootViewController", bundle: nil)
        masterViewFrame = CGRectMake(0, 0, self.view.frame.width, masterViewHeight)
        detailViewFrame = CGRectMake(0, masterViewHeight, self.view.frame.width, self.view.frame.height - masterViewHeight)
        detailOffScreenFrame = CGRectMake(detailViewFrame.origin.x, detailViewFrame.origin.y + detailViewFrame.height, detailViewFrame.width, detailViewFrame.height)
        detailOnScreenFrame = detailViewFrame
        self.addChildViewController(masterView!)
        self.addChildViewController(detailView!)
        masterView!.view.frame = masterViewFrame
        detailView!.view.frame = detailViewFrame
        self.view.addSubview(masterView!.view)
        self.view.addSubview(detailView!.view)
    }

    func cycleDetailView(from:UIViewController, toView to:UIViewController){
        from.willMoveToParentViewController(nil)
        self.addChildViewController(to)
        to.view.frame = self.detailOffScreenFrame
        self.detailView = to
        self.transitionFromViewController(from, toViewController: to, duration: 0.25, options: UIViewAnimationOptions.allZeros,
            animations: {() -> Void in

                // send the new view controller in, and the old one out
                to.view.frame = self.detailOnScreenFrame
                from.view.frame = self.detailOffScreenFrame
            }, completion: {success -> Void in

                // tells the view controllers cycling has ended
                from.removeFromParentViewController()
                to.didMoveToParentViewController(self)
            }
        )
    }

    func showDetailView(vc: UIViewController){
        if let oldView = detailView {
            cycleDetailView(oldView, toView: vc)
        }else{
            detailView = self.childViewControllers[1] as? UIViewController
            if let oldView = detailView {
                cycleDetailView(oldView, toView: vc)
            }else{

            }
        }
    }
}

问题出在showDetailView()。当这样被一段代码调用时：

    let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate
    if let delegateUnwrapped = appDelegate {
        delegateUnwrapped.appShowDetailView(aViewController)
    }

...容器函数showDetailView() 只能获取detailView 的nil 值，而self.childViewControllers 是一个空数组。

这让我觉得我以错误的方式访问子视图控制器。

谁能告诉我哪里出错了？

TIA。

【问题讨论】：

标签： ios swift uiviewcontroller appdelegate

【解决方案1】：

我认为您的问题是应用程序委托中的这一行，

 window?.rootViewController = Container()

这会创建一个新的 Container 实例，而不是您分配给 container 属性的那个实例。将该行更改为，

window?.rootViewController = container

【讨论】：