Swift iOS : 代码分析DrawController

仓库github/DrawController(github.com/sascha/Draw…)
是一个Swift语言编写的抽屉库。它能够传入一个中心视图控制器，一个左侧视图控制器，并由一个MaxDrawerWidth属性。建立完毕后，中心视图控制器的视图内容占据所有屏幕；当执行打开抽屉的函数时，整个中心控制的视图内容一块儿向右平移MaxDrawerWidth这么宽，而且显示左侧视图控制器的内容到屏幕上，内容占满屏幕，可是宽度不超过MaxDrawerWidth指定的值。

研究此代码库的时候，发现它是一个很好的解说Container View Controller[developer.apple.com/library/con…] 概念的例子。这里面：

1. 类DrawerController就是一个Container View Controller
2. 其余的视图控制器就是Child View Controller
3. 第一个类和其余类构成了父子关系
4. 视图控制器内的视图其实都是放置到DrawerController.view以内的

我把此库内的关于动画和手势的代码所有去掉，专门留下特定于这些控制器交互的代码留下。从1000多行的代码抽取出来247行的代码以下：

import UIKit
 var drawerController : DrawerPage?
 @UIApplicationMain
 class AppDelegate: UIResponder, UIApplicationDelegate {
    var window : UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        window = UIWindow()
        drawerController = DrawerPage()
        window!.rootViewController = drawerController
        window!.rootViewController!.view.backgroundColor = .blue
        window!.makeKeyAndVisible()
        return true
    }
 }
 class DrawerPage : DrawerBase{
    init(){
        super.init(CenterPage(),LeftPage())
    }
    // 哄编译器开心的代码
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
 }
 class DrawerBase : DrawerController{
    init(_ center : UIViewController,_ left : UIViewController){
        super.init(centerViewController: center, leftDrawerViewController: left)
    }
    // 从入门到入门：
    // 1. What exactly is init coder aDecoder?
    // 2. What does the question mark means in public init?(coder aDecoder: NSCoder)?
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
 }
 class LeftPage: UIViewController {
    var count = 0
    var label : UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .white
        label   = UILabel()
        label.frame = CGRect(x: 100, y: 100, width: 120, height: 50)
        label.text =  "Left"
        view.addSubview(label)
        let button   = UIButton(type: .system)
        button.frame = CGRect(x: 120, y: 150, width: 120, height: 50)
        button.setTitle("Close",for: .normal)
        button.addTarget(self, action: #selector(buttonAction(_:)), for: .touchUpInside)
        view.addSubview(button)
    }
    @objc func buttonAction(_ sender:UIButton!){
        drawerController?.toggleLeftDrawerSide(animated: true, completion: nil)
    }
 }
 class CenterPage: UIViewController {
    var label : UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .white
        label   = UILabel()
        label.frame = CGRect(x: 100, y: 100, width: 120, height: 50)
        label.text =  "Center"
        view.addSubview(label)
        let button   = UIButton(type: .system)
        button.frame = CGRect(x: 120, y: 150, width: 120, height: 50)
        button.backgroundColor = .blue
        button.setTitle("Left Page Drawer",for: .normal)
        button.addTarget(self, action: #selector(buttonAction(_:)), for: .touchUpInside)
        view.addSubview(button)
    }
    @objc func buttonAction(_ sender:UIButton!){
        drawerController?.toggleLeftDrawerSide(animated: true, completion: nil)
    }
    @objc func buttonAction1(_ sender:UIButton!){
//        drawerController?.toggleRightDrawerSide(animated: true, completion: nil)
    }
 }
 // code imple
 open class DrawerController: UIViewController {
    fileprivate var _centerViewController: UIViewController?
    fileprivate var _leftDrawerViewController: UIViewController?
    fileprivate var _leftDrawerWidth = DrawerDefaultWidth
    open var centerViewController: UIViewController? {
        get {
            return self._centerViewController
        }
    }
    open var leftDrawerViewController: UIViewController? {
        get {
            return self._leftDrawerViewController
        }
    }
    open var leftDrawerWidth: CGFloat {
        get {
            return self._leftDrawerWidth
        }
    }
    open var shadowRadius = DrawerDefaultShadowRadius
    open var shadowOpacity = DrawerDefaultShadowOpacity
    fileprivate lazy var childControllerContainerView: UIView = {
        let a = UIView(frame: self.view.bounds)
        self.view.addSubview(a)
        return a
    }()
    fileprivate lazy var centerContainerView: DrawerCenterContainerView = {
        let centerFrame = self.childControllerContainerView.bounds
        let centerContainerView = DrawerCenterContainerView(frame: centerFrame)
        centerContainerView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        centerContainerView.backgroundColor = UIColor.clear
        self.childControllerContainerView.addSubview(centerContainerView)
        return centerContainerView
    }()
    open fileprivate(set) var openSide: DrawerSide = .center {
        didSet {
            if self.openSide == .center {
                self.leftDrawerViewController?.view.isHidden = true
            }
            self.setNeedsStatusBarAppearanceUpdate()
        }
    }
    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    }
    public init(centerViewController: UIViewController, leftDrawerViewController: UIViewController?) {
        super.init(nibName: nil, bundle: nil)
        self.setCenter(centerViewController)
        self.setDrawer(leftDrawerViewController,for:.left)
    }
    fileprivate func childViewController(for drawerSide: DrawerSide) -> UIViewController? {
        var childViewController: UIViewController?
        switch drawerSide {
        case .left:
            childViewController = self.leftDrawerViewController
        case .center:
            childViewController = self.centerViewController
        }
        return childViewController
    }
    fileprivate func sideDrawerViewController(for drawerSide: DrawerSide) -> UIViewController? {
        var sideDrawerViewController: UIViewController?
        if drawerSide != .center {
            sideDrawerViewController = self.childViewController(for: drawerSide)
        }
        return sideDrawerViewController
    }
    fileprivate func updateShadowForCenterView() {
        self.centerContainerView.layer.masksToBounds = false
        self.centerContainerView.layer.shadowRadius = shadowRadius
        self.centerContainerView.layer.shadowOpacity = shadowOpacity
        if let shadowPath = centerContainerView.layer.shadowPath {
            let currentPath = shadowPath.boundingBoxOfPath
            if currentPath.equalTo(centerContainerView.bounds) == false {
                centerContainerView.layer.shadowPath = UIBezierPath(rect: centerContainerView.bounds).cgPath
            }
        } else {
            self.centerContainerView.layer.shadowPath = UIBezierPath(rect: self.centerContainerView.bounds).cgPath
        }
    }
    open func toggleLeftDrawerSide(animated: Bool, completion: ((Bool) -> Void)?) {
        self.toggleDrawerSide(.left, animated: animated, completion: completion)
    }
    open func toggleDrawerSide(_ drawerSide: DrawerSide, animated: Bool, completion: ((Bool) -> Void)?) {
        assert({ () -> Bool in
            return drawerSide != .center
        }(), "drawerSide cannot be .None")
        if self.openSide == DrawerSide.center {
            self.openDrawerSide(drawerSide,completion: completion)
        } else {
            if (drawerSide == DrawerSide.left && self.openSide == DrawerSide.left) {
                self.closeDrawer(animated: animated, completion: completion)
            } else if completion != nil {
                completion!(false)
            }
        }
    }
    fileprivate func openDrawerSide(_ drawerSide: DrawerSide,completion: ((Bool) -> Void)?) {
        assert({ () -> Bool in
            return drawerSide != .center
        }(), "drawerSide cannot be .None")
        if let vc = self.leftDrawerViewController{
            vc.view.isHidden = false
            var newFrame: CGRect
            newFrame = view.frame
            newFrame.size.width = _leftDrawerWidth
            vc.view.frame = newFrame
            //            vc.view.frame = vc.evo_visibleDrawerFrame
        }
        func panRight(_ view : UIView,_ value : CGFloat){
            var newFrame: CGRect
            newFrame = view.frame
            newFrame.origin.x = value
            view.frame = newFrame
        }
        panRight(centerContainerView, _leftDrawerWidth)
        self.openSide = drawerSide
    }
    fileprivate func setDrawer(_ vc: UIViewController?, for drawerSide: DrawerSide) {
        assert({ () -> Bool in
            return drawerSide != .center
        }(), "drawerSide cannot be .None")
        let currentSideViewController = self.sideDrawerViewController(for: drawerSide)
        if currentSideViewController == vc {
            return
        }
        self._leftDrawerViewController = vc
        if vc != nil {
            self.addChildViewController(vc!)
            vc!.didMove(toParentViewController: self)
            self.childControllerContainerView.addSubview(vc!.view)
            self.childControllerContainerView.sendSubview(toBack: vc!.view)
            vc!.view.isHidden = true
        }
    }
    fileprivate func setCenter(_ vc: UIViewController?) {
        self._centerViewController = vc
        if vc != nil {
            self.addChildViewController(vc!)
            vc!.didMove(toParentViewController: self)
            self.centerContainerView.addSubview(vc!.view)
            self._centerViewController!.view.frame = self.centerContainerView.bounds
            self.updateShadowForCenterView()
        }
    }
    open func closeDrawer(animated: Bool, completion: ((Bool) -> Void)?) {
        let newFrame = self.childControllerContainerView.bounds
        self.setNeedsStatusBarAppearanceUpdate()
        self.centerContainerView.frame = newFrame
        self.openSide = .center
    }
    open override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.black
    }
    static let DrawerDefaultWidth: CGFloat = 210.0 //280.0
    static let DrawerDefaultShadowRadius: CGFloat = 10.0
    static let DrawerDefaultShadowOpacity: Float = 0.8
    typealias  DrawerCenterContainerView =  UIView
    public enum DrawerSide: Int {
        case center
        case left
    }
 }复制代码

这里的代码，很关键的是在DrawerController内的view中，建立了一个子视图叫作childControllerContainerView，其内在建立一个子视图centerContainerView，它们几个的大小都是屏幕大小，视图层次为：

--view
----childControllerContainerView
------centerContainerView复制代码

并约定好:

1. 所有的Center View Controller的视图所有放置到centerContainerView内
2. 所有的left View Controller和right View Controller的视图所有放置到centerContainerView内
3. left View Controller和right View Controller的视图放置完毕后，须要首先隐藏起来，而且sendToBack，保证它是不可见的，也不会遮挡任何Center View Controller的内容

这样当指定打开抽屉函数时，centerContainerView总体平移，若是打开左边的抽屉，就向右移动，反之亦然。从而Center View Controller的视图也就跟着平移。并同时把抽屉视图（left View Controller和right View Controller的视图）显示出来，可是宽度不超过MaxDrawerWidth。

经过以上分析，能够增强对Container View Controller概念的理解。