通过一个“根”视图控制器控制多个子视图控制器答案

【问题标题】：Controlling multiple children ViewControllers through one 'root' ViewController通过一个“根”视图控制器控制多个子视图控制器
【发布时间】：2017-04-17 21:23:16
【问题描述】：

我正在创建一个具有根视图控制器的应用程序。这个根视图控制器是许多其他子视图控制器的父级，它们是应用程序中的主要状态。

由于我在根的viewDidLoad 的开头将子项添加到根，因此所有子项的 viewDid 和 viewWill 方法都会在添加到根时触发，而不是在我选择显示子视图控制器时触发。

有没有人知道在需要时避免孩子的 viewDid 或 viewWill 方法的好方法？如果没有，有没有办法对这些子视图控制器进行一些控制？请，谢谢！

根视图控制器：

override func viewDidLoad() {
    super.viewDidLoad()

    guard let storyboard = storyboard else {
        print("ERROR: No storyboard found! Early return")
        return
    }

    // Introduction
    let introVC = storyboard.instantiateViewController(withIdentifier: "IntroID") as! IntroductionViewController
    self.configureChildViewController(childController: introVC, onView: self.view)

    // Login
    let loginVC = storyboard.instantiateViewController(withIdentifier: "LoginID") as! LoginViewController
    self.configureChildViewController(childController: loginVC, onView: self.view)

    // Move to the first VC
    self.goToVC(childVC: introVC)
}

移动到新的子视图控制器

func goToVC(childVC: UIViewController) {

    // Bring child to front
    self.view.bringSubview(toFront: childVC.view)

    // Create the moveTo animations to the VC
    childVC.didMove(toParentViewController: self)
}

子类的配置

extension UIViewController {
func configureChildViewController(childController: UIViewController, onView: UIView) {

    if let view = childController.view {

        // Add the view controller
        addChildViewController(childController)

        // Add and resize the subview
        onView.addSubview(view)
        constrainViewEqual(holderView: onView, view: view)
    } else {
        print("ERROR: The child controller has no usable view")
    }
}

func constrainViewEqual(holderView: UIView, view: UIView) {
    view.translatesAutoresizingMaskIntoConstraints = false
    // Create the view's new constraints
    let pinTop    = self.createConstraint(ofType: .top,    inView: holderView, newView: view)
    let pinBottom = self.createConstraint(ofType: .bottom, inView: holderView, newView: view)
    let pinLeft   = self.createConstraint(ofType: .left,   inView: holderView, newView: view)
    let pinRight  = self.createConstraint(ofType: .right,  inView: holderView, newView: view)

    // Add the constraints
    holderView.addConstraints([pinTop, pinBottom, pinLeft, pinRight])
}

private func createConstraint(ofType: NSLayoutAttribute, inView: UIView, newView: UIView) -> NSLayoutConstraint {
    return NSLayoutConstraint( item:       newView,
                               attribute:  ofType,
                               relatedBy:  .equal,
                               toItem:     inView,
                               attribute:  ofType,
                               multiplier: 1.0,
                               constant:   0)
}

【问题讨论】：

标签： ios swift swift3

【解决方案1】：

我能给你的最好建议是不要一次将所有子视图控制器添加到父视图控制器。一次最多维护一个子视图控制器。

func goToVC(childVC: UIViewController) {
    if childViewControllers.count == 0 {

        self.addChildViewController(childVC)
        childVC.view.frame = containerView.bounds
        self.containerView.addSubview(childVC.view)
        childVC.didMove(toParentViewController: self)

    } else {

        let oldViewController = self.childViewControllers[0]
        childVC.view.frame = oldViewController.view.frame
        oldViewController.willMove(toParentViewController: nil)
        self.addChildViewController(childVC)
        self.transition(from: oldViewController, to: childVC, duration: 0, options: .transitionCrossDissolve, animations: nil) { completed in
            oldViewController.removeFromParentViewController()
            childVC.didMove(toParentViewController: self)
        }
    }
}

【讨论】：