var leftView: UIView?
    var minX: CGFloat?
    var midX: CGFloat?
    var maxX:CGFloat?
    /*
     抽屜
     */
    func drawerView(){
        self.view.isMultipleTouchEnabled = true
        self.view.isUserInteractionEnabled = true
        self.view.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(self.pan(_:))))
        let make = CGRect(x: -UIScreen.main.bounds.width*3/5, y: 0, width: UIScreen.main.bounds.width*3/5, height: UIScreen.main.bounds.height)
        leftView = UIView(frame: make)
        leftView?.backgroundColor = UIColor.brown
        self.view.addSubview(leftView!)
        minX = leftView?.center.x
        maxX = minX! + make.width
        midX = (maxX!-minX!)/2 + minX!
    
    }
func pan(_ pan: UIPanGestureRecognizer){
        
        switch pan.state{
        
        case UIGestureRecognizerState.began:
            print("----began----")
            
        case UIGestureRecognizerState.changed:
            print("----Changed----")
            let tran = pan.translation(in: self.view)
            let newC = (leftView?.center.x)! + tran.x
            if newC >= minX && newC <= maxX{
                leftView?.center = CGPoint(x: newC, y: (leftView?.center.y)!)
            }
            pan.setTranslation(CGPoint.zero, in: self.view)
        case UIGestureRecognizerState.ended:
                UIView.animate(withDuration: 0.2, animations: { () -> Void in
                if self.leftView!.center.x > self.minX && self.leftView!.center.x < self.midX{
                    self.leftView!.center = CGPoint(x: self.minX!, y: self.leftView!.center.y)
                }else if self.leftView!.center.x >= self.midX && self.leftView!.center.x < self.maxX{
                    self.leftView!.center = CGPoint(x: self.maxX!, y: self.leftView!.center.y)
                }
                }, completion: { (finish) -> Void in
                    
            })
            
        default: break
        }
    
    }