导读

• 简单用Swift写了一个抽屉效果,可以直接使用并且简单;
• 很多软件都运了抽屉效果，比如qq的左抽屉，英雄联盟,滴滴打车，和uber等等都运用了抽屉;
• GitHub上有代表性的是MMDrawerController.

• GitHub地址：https://github.com/wangliujiayou/DrawerView 欢迎Star.

效果

image.gif

iOS抽屉式结构实现分析

• 主要是在控制器的View上添加了两个View,一个左侧leftView和一个mainView。这里我们自定义一个DrawerViewController，init(mainVC: UIViewController, leftMenuVC: UIViewController, leftWidth: CGFloat)设置，一个mainVC，一个leftMenuVC，和一个宽度,将mainVC和leftMenuVC的view添加到controller的view上（menuVC的view在下面）。

        view.addSubview(leftMenuVC.view)
        view.addSubview(mainVC.view)
        
        addChildViewController(leftMenuVC)
        addChildViewController(mainVC)

• 然后首先实现点击方法openLeftMenu和closeLeftMenu（这两个方法主要是计算mainVC的view的位置）方便以后调用。

//MARK: - 打开左侧菜单
    func openLeftMenu() {
        
        UIView.animate(withDuration: 0.25, delay: 0, options: UIViewAnimationOptions.curveLinear, animations: {
        
            self.leftVC?.view.transform = CGAffineTransform.identity
            self.mainVC?.view.transform = CGAffineTransform(translationX: self.maxWidth, y: 0)
            
        
        }, completion: {
        
            (finish: Bool) -> () in
            
            self.mainVC?.view.addSubview(self.coverBtn)
            
        })
        
    }
    
    //MARK: - 关闭左侧菜单
    func closeLeftMenu() {
        
        UIView.animate(withDuration: 0.25, delay: 0, options: UIViewAnimationOptions.curveLinear, animations: {
            
            self.leftVC?.view.transform = CGAffineTransform(translationX: -self.maxWidth, y: 0)
            self.mainVC?.view.transform = CGAffineTransform.identity
            
            
        }, completion: {
            
            (finish: Bool) -> () in
            
            self.coverBtn.removeFromSuperview()
            
        })
        
        
    }

• 最后给mainVC的view添加屏幕边缘手势，实现mainVC的view跟随手指移动。
  循环遍历view给每一个一级视图添加手势

for childViewController in (mainVC?.childViewControllers)! {
            
            addScreenEdgePanGestureRecognizerToView(view: childViewController.view)
            
        }

//MARK: - 添加屏幕边缘手势
    private func addScreenEdgePanGestureRecognizerToView(view: UIView) {
        
        let pan = UIScreenEdgePanGestureRecognizer(target: self, action: #selector(edgPanGesture(_:)))
        pan.edges = UIRectEdge.left
        view.addGestureRecognizer(pan)
        
    }

• 在平移手势调用的方法中，通过偏移量来确定mainView的frame，实现动画效果

  • 首先通过pan.translation(in: pan.view).x方法获取偏移量,通过偏移量的正负确定拖动的方向
  • 当手指松开后需要根据mainView的x值确定其视图是定位到原始位置还是其缩放的位置

• 打开手势

//MARK: - 屏幕左边缘手势
    func edgPanGesture(_ pan: UIScreenEdgePanGestureRecognizer) {
        
        let offsetX = pan.translation(in: pan.view).x
        
        if pan.state == UIGestureRecognizerState.changed && offsetX <= maxWidth {
            
            mainVC?.view.transform = CGAffineTransform(translationX: max(offsetX, 0), y: 0)
            leftVC?.view.transform = CGAffineTransform(translationX: -maxWidth + offsetX, y: 0)
            
        } else if pan.state == UIGestureRecognizerState.ended || pan.state == UIGestureRecognizerState.cancelled || pan.state == UIGestureRecognizerState.failed {
            
            if offsetX > screenW * 0.5 {
                
                openLeftMenu()
                
            } else {
                
                closeLeftMenu()
            }
            
        }
        
    }

• 关闭遮盖手势

//MARK: - 遮盖按钮手势
    func panCloseLeftMenu(_ pan: UIPanGestureRecognizer) {
        
        let offsetX = pan.translation(in: pan.view).x
        if offsetX > 0 {return}
        
        if pan.state == UIGestureRecognizerState.changed && offsetX >= -maxWidth {
            
            let distace = maxWidth + offsetX
            
            mainVC?.view.transform = CGAffineTransform(translationX: distace, y: 0)
            leftVC?.view.transform = CGAffineTransform(translationX: offsetX, y: 0)
            
        } else if pan.state == UIGestureRecognizerState.ended || pan.state == UIGestureRecognizerState.cancelled || pan.state == UIGestureRecognizerState.failed {
            
            if offsetX > screenW * 0.5 {
                
                openLeftMenu()
                
            } else {
                
                closeLeftMenu()
            }
            
        }
        
    }

UIPresentationController简介

• UIPresentationController是 iOS8 新增的一个API，苹果的官方定义是：对象为所呈现的视图控制器提供高级视图的转换管理（从呈现视图控制器的时间直到它被消除期间）;
• iOS 8以前就是自定义view,去画一个三角和长方形;
• 简单直接的方法用图片

直接贴代码不讲废话

@IBAction func showAlert(_ sender: UIBarButtonItem) {
        
        let popVC = PopViewController()
        popVC.modalPresentationStyle = UIModalPresentationStyle.popover
        popVC.popoverPresentationController?.barButtonItem = sender
        popVC.popoverPresentationController?.delegate = self
        //可控制三角颜色
        popVC.popoverPresentationController?.backgroundColor = UIColor.white
        present(popVC, animated: true, completion: nil)
        
    }


    func adaptivePresentationStyle(for controller: UIPresentationController) -> UIModalPresentationStyle {
        return UIModalPresentationStyle.none
    }
    
    func popoverPresentationControllerShouldDismissPopover(_ popoverPresentationController: UIPopoverPresentationController) -> Bool {
        return true
    }

具体代码可以从这里下载,后续还有更实用的功能.