UIScrollView

let scaleFactor = scrollView.bounds.width / imageView.bounds.width 
scrollView.minimumZoomScale = scaleFactor
scrollView.zoomScale = scaleFactor

extension DetailViewController: UIScrollViewDelegate {
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}

对子视图的布局进行修改的时候 最好放在viewDidLayoutSubviews 或者 viewDidAppear里面

想把缩放的内容始终居中

override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        let scaleFactor = scrollView.bounds.width / imageView.bounds.width
        scrollView.minimumZoomScale = scaleFactor
        //会受当前minimumZoomScale 和 maximumZoomSCale 的值的现值 所以必须在min和max设置之后
        scrollView.zoomScale = scaleFactor
        
    }

func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat) {
        
        if imageView.frame.height < scrollView.frame.height {
            
            let offsetY = (scrollView.frame.height - imageView.frame.height) / 2
            imageView.center = CGPoint(x: imageView.frame.width / 2, y: imageView.frame.height / 2 + offsetY)
        }
    }

当图片过长 无法全屏显示的时候 可以改变scrollView.contentInsetAdjustmentBehavior = .never

        //滚动条的样式
        scrollView.indicatorStyle = .default
        //是否启动分页机制
        scrollView.isPagingEnabled = false
        //锁定
    /*如果此属性为false，则允许在水平和垂直方向滚动。如果此属性为true，并且用户开始沿一个常规方向（水平或垂直）拖动，则滚动视图将禁用沿另一个方向的滚动。如果拖动方向是对角线，则滚动将不会被锁定，用户可以在拖动完成之前向任何方向拖动。默认值为false
         */
        scrollView.isDirectionalLockEnabled = false
        //反弹
        scrollView.bounces = true
        //
        scrollView.alwaysBounceVertical = false
        scrollView.alwaysBounceHorizontal = false
        //缩放的时候的反弹
        scrollView.bouncesZoom = true
        scrollView.minimumZoomScale = 1
        scrollView.maximumZoomScale = 1
        scrollView.zoomScale = 0.2
        scrollView.setZoomScale(0.2, animated: true)
        //把视图缩放到指定大小
        scrollView.zoom(to: CGRect(x: 1, y: 1, width: 50, height: 50), animated: true)
        //拖拽的时候键盘也不消失
        scrollView.keyboardDismissMode = .none
        
        //
        scrollView.isDragging
        scrollView.isTracking
        scrollView.isDecelerating//减速
        scrollView.isZooming //是否在进行缩放
        scrollView.isZoomBouncing//是否在进行缩放的回弹
        
        scrollView.panGestureRecognizer
        scrollView.pinchGestureRecognizer
        
        //减速速率
        scrollView.decelerationRate = .normal
        
        //返回顶部 只限于当前Controller里面只有一个scrollview才有效果 多个的就没有效果
        scrollView.scrollsToTop = true

RefreshControl

   data.append("rrwew")
   tableView.reloadData()
   DispatchQueue.main.async {
       self.tableView.refreshControl?.endRefreshing()
   }

let refreshControl = UIRefreshControl()
refreshControl.tintColor = #colorLiteral(red: 1, green: 0.1491314173, blue: 0, alpha: 1)
refreshControl.attributedTitle = NSAttributedString(string: "加载中", attributes: [.foregroundColor : UIColor(red: 1, green: 0.1491314173, blue: 0, alpha: 1)])
tableView.refreshControl = refreshControl
tableView.refreshControl?.addTarget(self, action: #selector(refresh), for: .valueChanged)