Swift4.1转场动画实现侧滑抽屉效果

实现使用了Modal转场动画，原因是项目多由导航控制器和标签控制器作为基类，为了不影响导航控制器的代理，转场动画使用模态交互。

代码使用SnapKit进行布局，能够适应屏幕旋转。手势速率大于300或进度超过30%的时候直接完成动画，否则动画回滚取消，具体数值可以修改对应的常量。抽屉出现的时候，主控制有遮罩，对应关键字是mask。

实现文件只有两个

DrawerControl：控制抽屉出现，一行代码即可调用

Animator：负责动画实现，包括了交互式的代理事件和非交互式的代理事件

//
// DrawerControl.swift
// PratiseSwift
//
// Created by EugeneLaw on 2018/7/31.
// Copyright © 2018年 EugeneLaw. All rights reserved.
//

import UIKit

enum DrawerSize {
 case Left
 case Right
}

class DrawerControl: NSObject {

 /**主页面*/
 var base: UIViewController?
 /**抽屉控制器*/
 var drawer: UIViewController?
 /**抽屉在左边还是右边，默认左边，没有实现右边，要右边自己去animator里面加判断*/
 var whichSize = DrawerSize.Left
 /**拖拽手势*/
 var panBase: UIPanGestureRecognizer?
 var panDrawer: UIPanGestureRecognizer?
 /**主页面在抽屉显示时保留的宽度*/
 var baseWidth: CGFloat {
  get {
   return self.animator!.baseWidth
  }
  set {
   self.animator?.baseWidth = newValue
  }
 }
 /**是否应该响应手势*/
 var shouldResponseRecognizer = false
 /**效果响应*/
 var animator: Animator?

 init(base: UIViewController, drawer: UIViewController) {
  super.init()
  self.base = base
  self.drawer = drawer
  animator = Animator(base: self.base!, drawer: self.drawer!)
  self.panBase = UIPanGestureRecognizer(target: self, action: #selector(panBaseAction(pan:)))
  base.view.addGestureRecognizer(self.panBase!)
  self.panDrawer = UIPanGestureRecognizer(target: self, action: #selector(panDrawerAction(pan:)))
  drawer.view.addGestureRecognizer(self.panDrawer!)
  self.drawer?.transitioningDelegate = self.animator
 }

 deinit {
  if self.panBase != nil {
   self.base?.view.removeGestureRecognizer(self.panBase!)
   self.panBase = nil
  }
  if self.panDrawer != nil {
   self.drawer?.view.removeGestureRecognizer(self.panDrawer!)
   self.panDrawer = nil
  }
 }

}

extension DrawerControl {

 ///显示抽屉
 func show() {
  if (self.base?.view.frame.origin.x)! > SCREEN_WIDTH/2 {
   return
  }
  self.animator?.interative = false
  self.base?.present(self.drawer!, animated: true, completion: nil)
 }

 ///关闭抽屉，或直接dismiss即可
 func close() {
  self.animator?.interative = false
  self.drawer?.dismiss(animated: true, completion: nil)
 }

}

extension DrawerControl {

 @objc func panBaseAction(pan: UIPanGestureRecognizer) {
  let transition = pan.translation(in: self.drawer?.view)
  let percentage = CGFloat(transition.x/SCREEN_WIDTH)
  let velocity = CGFloat(fabs(pan.velocity(in: self.drawer?.view).x))
  switch pan.state {
  case .began:
   if transition.x < 0 {
    shouldResponseRecognizer = false
   }else {
    shouldResponseRecognizer = true
   }
   if shouldResponseRecognizer {
    self.beginAnimator(showDrawer: true)
   }
  case .changed:
   if shouldResponseRecognizer {
    self.updateAnimator(percentage)
   }
  default:
   if shouldResponseRecognizer {
    self.cancelAnimator(percentage, velocity: velocity)
   }
  }
 }

 @objc func panDrawerAction(pan: UIPanGestureRecognizer) {
  let transition = pan.translation(in: self.drawer?.view)
  let percentage = CGFloat(-transition.x/SCREEN_WIDTH)
  let velocity = CGFloat(fabs(pan.velocity(in: self.drawer?.view).x))
  switch pan.state {
  case .began:
   if transition.x > 0 {
    shouldResponseRecognizer = false
   }else {
    shouldResponseRecognizer = true
   }
   if shouldResponseRecognizer {
    self.beginAnimator(showDrawer: false)
   }
  case .changed:
   if shouldResponseRecognizer {
    self.updateAnimator(percentage)
   }
  default:
   if shouldResponseRecognizer {
    self.cancelAnimator(percentage, velocity: velocity)
   }
  }
 }

 func beginAnimator(showDrawer: Bool) {
  self.animator?.interative = true
  if showDrawer {
   self.base?.transitioningDelegate = self.animator
   self.base?.present(self.drawer!, animated: true, completion: nil)
  }else {
   self.drawer?.transitioningDelegate = self.animator
   self.drawer?.dismiss(animated: true, completion: nil)
  }
 }

 func updateAnimator(_ percentage: CGFloat) {
  self.animator?.update(percentage)
 }

 func cancelAnimator(_ percentage: CGFloat, velocity: CGFloat) {
  if percentage < 0.3 && velocity < 300 {
   self.animator?.cancel()
  }else {
   self.animator?.finish()
  }
 }

}

//
// Animator.swift
// PratiseSwift
//
// Created by EugeneLaw on 2018/7/31.
// Copyright © 2018年 EugeneLaw. All rights reserved.
//

import UIKit

let DRAWER_ANIMATION_TIME = 0.3

class Animator: UIPercentDrivenInteractiveTransition, UIViewControllerTransitioningDelegate, UIViewControllerAnimatedTransitioning {

 /**是否交互转场*/
 var interative = false
 var showDrawer = false
 var base: UIViewController?
 var drawer:UIViewController?
 /**主页面在抽屉显示时保留的宽度*/
 var baseWidth: CGFloat = 100
 lazy var mask = { () -> UIButton in
  let mask = UIButton()
  mask.addTarget(self, action: #selector(maskClicked(_:)), for: .touchUpInside)
  return mask
 }()

 init(base: UIViewController, drawer: UIViewController) {
  super.init()
  self.base = base
  self.drawer = drawer
  UIDevice.current.beginGeneratingDeviceOrientationNotifications()
  NotificationCenter.default.addObserver(self, selector: #selector(observeDeviceOrientation(_:)), name: .UIDeviceOrientationDidChange, object: nil)
 }

 @objc func observeDeviceOrientation(_ notification: NSObject) {
  if let superView = self.base?.view.superview {
   if showDrawer {
    self.base?.view.snp.remakeConstraints({ (make) in
     make.width.equalTo(SCREEN_WIDTH)
     make.left.equalTo(superView.snp.right).offset(-self.baseWidth)
     make.top.bottom.equalTo(superView)
    })
   }else {
    self.base?.view.snp.remakeConstraints({ (make) in
     make.edges.equalTo(superView)
    })
   }
   superView.layoutIfNeeded()
  }
 }

 deinit {
  NotificationCenter.default.removeObserver(self)
 }

}

extension Animator {

 func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
  if showDrawer {
   let fromView = transitionContext.view(forKey: .from)
   addShadowToView(fromView!, color: .black, offset: CGSize(width: -1, height: 0), radius: 3, opacity: 0.1)
   let toView = transitionContext.view(forKey: .to)
   let containerView = transitionContext.containerView
   containerView.addSubview(toView!)
   containerView.addSubview(fromView!)
   fromView?.snp.remakeConstraints({ (make) in
    make.edges.equalTo(containerView)
   })
   toView?.snp.remakeConstraints({ (make) in
    make.edges.equalTo(containerView)
   })
   containerView.layoutIfNeeded()
   UIView.animate(withDuration: DRAWER_ANIMATION_TIME, animations: {
    fromView?.snp.remakeConstraints({ (make) in
     make.left.equalTo((toView?.snp.right)!).offset(-self.baseWidth)
     make.width.top.bottom.equalTo(toView!)
    })
    containerView.layoutIfNeeded()
   }) { (finish) in
    let cancel = transitionContext.transitionWasCancelled
    transitionContext.completeTransition(!cancel)
    if !cancel {//取消状态下区分添加到哪一个父视图，弄错会导致黑屏
     if self.drawer?.view.superview != nil {
      self.drawer?.view?.snp.remakeConstraints({ (make) in
       make.edges.equalTo((self.drawer?.view?.superview)!)
      })
     }
     self.showPartOfView()
    }else {
     fromView?.snp.remakeConstraints({ (make) in
      make.edges.equalTo((fromView?.superview)!)
     })
    }
   }
  }else {
   let fromView = transitionContext.view(forKey: .from)
   let toView = transitionContext.view(forKey: .to)
   addShadowToView(toView!, color: .black, offset: CGSize(width: -1, height: 0), radius: 3, opacity: 0.1)
   let containerView = transitionContext.containerView
   containerView.addSubview(fromView!)
   containerView.addSubview(toView!)
   fromView?.snp.remakeConstraints({ (make) in
    make.edges.equalTo(containerView)
   })
   toView?.snp.remakeConstraints({ (make) in
    make.left.equalTo(containerView.snp.right).offset(-self.baseWidth)
    make.width.equalTo(SCREEN_WIDTH)
    make.height.equalTo(SCREEN_HEIGHT)
    make.top.bottom.equalTo(containerView)
   })
   containerView.layoutIfNeeded()
   UIView.animate(withDuration: DRAWER_ANIMATION_TIME, animations: {
    toView?.snp.remakeConstraints({ (make) in
     make.edges.equalTo(containerView)
    })
    containerView.layoutIfNeeded()
   }) { (finish) in
    let cancel = transitionContext.transitionWasCancelled
    transitionContext.completeTransition(!cancel)
    toView?.snp.remakeConstraints({ (make) in
     make.edges.equalTo((toView?.superview)!)
    })
    if minX((self.base?.view)!) <= 0 {//判断结束时候是否回到主视图
     self.base?.view.isUserInteractionEnabled = true
    }
   }
  }
 }

 func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
  return DRAWER_ANIMATION_TIME
 }

 override func startInteractiveTransition(_ transitionContext: UIViewControllerContextTransitioning) {
  super.startInteractiveTransition(transitionContext)
 }

 func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
  self.showDrawer = true
  return self
 }

 func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
  self.showDrawer = false
  return self
 }

 func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
  if interative {
   return self
  }else {
   return nil
  }
 }

 func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
  if interative {
   return self
  }else {
   return nil
  }
 }

}

extension Animator {

 func showPartOfView() {
  self.drawer?.view.addSubview((self.base?.view)!)
  self.base?.view.snp.remakeConstraints({ (make) in
   make.left.equalTo((self.drawer?.view.snp.right)!).offset(-self.baseWidth)
   make.top.bottom.equalTo((self.drawer?.view)!)
   make.width.equalTo(SCREEN_WIDTH)
  })
  //遮罩
  self.drawer?.view.insertSubview(mask, aboveSubview: (self.base?.view)!)
  self.base?.view.isUserInteractionEnabled = false//阻止交互
  mask.snp.remakeConstraints { (make) in
   make.left.equalTo((mask.superview?.snp.right)!).offset(-baseWidth)
   make.top.width.bottom.equalTo(mask.superview!);
  }
  self.drawer?.view.superview?.layoutIfNeeded()
 }

 @objc func maskClicked(_ button: UIButton) {
  button.removeFromSuperview()
  self.drawer?.dismiss(animated: true, completion: nil)
 }

}

按钮调用例子：（手势控制已经自动添加到主控制器和抽屉控制器的view上）

创建推出抽屉的控制类，参数分别是主控制器和抽屉控制器。在我自己的练习工程中，把这个控制类定义为总控制器（包括了导航控制器和标签控制器的控制类）的一个属性。创建这个抽屉控制类的时候，我把导航控制器（它的root是标签控制器）当做主控制器传给第一个参数。

self.drawer = DrawerControl(base: self.navigation!, drawer: self.drawerPage) 

调用的时候只需要使用抽屉控制类的show方法即可，练习工程中我把该按钮封装在导航菜单里面，它响应的时候会调用总控制器的单例，调用单例记录的抽屉控制器属性。

@objc func btnMenuClicked(_ button: UIButton) {
 TotalControl.instance().drawer?.show()
}

附录：用到的一些变量

//
// Headers.swift
// PratiseSwift
//
// Created by EugeneLaw on 2018/7/23.
// Copyright © 2018年 EugeneLaw. All rights reserved.
//

import UIKit

//MARK: 设备
let isRetina = (UIScreen.instancesRespond(to: #selector(getter: UIScreen.currentMode)) ? __CGSizeEqualToSize(CGSize(width: 640, height: 960), (UIScreen.main.currentMode?.size)!) : false)
let iPhone5 = (UIScreen.instancesRespond(to: #selector(getter: UIScreen.currentMode)) ? __CGSizeEqualToSize(CGSize(width: 640, height: 1136), (UIScreen.main.currentMode?.size)!) : false)
let iPhone6 = (UIScreen.instancesRespond(to: #selector(getter: UIScreen.currentMode)) ? __CGSizeEqualToSize(CGSize(width: 750, height: 1334), (UIScreen.main.currentMode?.size)!) : false)
let iPhone6Plus = (UIScreen.instancesRespond(to: #selector(getter: UIScreen.currentMode)) ? __CGSizeEqualToSize(CGSize(width: 1242, height: 2208), (UIScreen.main.currentMode?.size)!) : false)
let isPad = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.pad)
let isPhone = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.phone)
let isiPhoneX = (UIScreen.instancesRespond(to: #selector(getter: UIScreen.currentMode)) ? __CGSizeEqualToSize(CGSize(width: 1125, height: 2436), (UIScreen.main.currentMode?.size)!) : false)

//MARK: 界面
let TABBAR_HEIGHT = (isiPhoneX ? 83 : 49)
let NAVIGATION_HEIGHT = (isiPhoneX ? 88 : 64)
var SCREEN_WIDTH: CGFloat {
 get {
  return SCREEN_WIDTH_FUNC()
 }
}
var SCREEN_HEIGHT: CGFloat {
 get {
  return SCREEN_HEIGHT_FUNC()
 }
}

func SCREEN_WIDTH_FUNC() -> CGFloat {
 return UIScreen.main.bounds.size.width
}

func SCREEN_HEIGHT_FUNC() -> CGFloat {
 return UIScreen.main.bounds.size.height
}

//MARK: 颜色
let COLOR_WHITESMOKE = ColorHex("#F5F5F5")

/**
 *十六进制颜色值转换成UIColor
 *@param "#000000"
 */
func ColorHex(_ color: String) -> UIColor? {
 if color.count <= 0 || color.count != 7 || color == "(null)" || color == "<null>" {
  return nil
 }
 var red: UInt32 = 0x0
 var green: UInt32 = 0x0
 var blue: UInt32 = 0x0
 let redString = String(color[color.index(color.startIndex, offsetBy: 1)...color.index(color.startIndex, offsetBy: 2)])
 let greenString = String(color[color.index(color.startIndex, offsetBy: 3)...color.index(color.startIndex, offsetBy: 4)])
 let blueString = String(color[color.index(color.startIndex, offsetBy: 5)...color.index(color.startIndex, offsetBy: 6)])
 Scanner(string: redString).scanHexInt32(&red)
 Scanner(string: greenString).scanHexInt32(&green)
 Scanner(string: blueString).scanHexInt32(&blue)
 let hexColor = UIColor.init(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: 1)
 return hexColor
}

/**
 *给图层添加阴影
 */
func addShadowToView(_ view: UIView, color: UIColor, offset: CGSize, radius: CGFloat, opacity: Float) {
 view.layer.shadowColor = color.cgColor
 view.layer.shadowOffset = offset
 view.layer.shadowOpacity = opacity
 view.layer.shadowRadius = radius
}

/**
 *计算图层的宽度
 */
func width(_ object: UIView) -> CGFloat {
 return object.frame.width
}

/**
 *在父视图中的x坐标
 */
func minX(_ object: UIView) -> CGFloat {
 return object.frame.origin.x
}

/**
 *在父视图中的x坐标+自身宽度
 */
func maxX(_ object: UIView) -> CGFloat {
 return object.frame.origin.x+width(object)
}

/**
 *在父视图中的y坐标
 */
func minY(_ object: UIView) -> CGFloat {
 return object.frame.origin.y
}

/**
 *在父视图中的y坐标+自身高度
 */
func maxY(_ object: UIView) -> CGFloat {
 return object.frame.origin.y+height(object)
}

/**
 *计算图层的高度
 */
func height(_ object: UIView) -> CGFloat {
 return object.frame.height
}

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