iOS10.0自带的刷新控件UIRefreshControl简介

 @available(iOS 10.0, *)open var refreshControl: UIRefreshControl?

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class ViewController: UIViewController {    var scrollView: UIScrollView?    override func viewDidLoad() {        super.viewDidLoad()        // 创建UIScrollView        let scrollView = UIScrollView(frame: UIScreen.main.bounds)        // 初始化UIScrollView        let v = UIView(frame: CGRect(x: 0, y: 0, width: scrollView.frame.width, height: 700))        v.backgroundColor = UIColor.purple        scrollView.addSubview(v)        scrollView.contentSize = v.frame.size        self.view.addSubview(scrollView)        self.scrollView = scrollView        // 创建UIRefreshControl        let refreshControl = UIRefreshControl()        scrollView.refreshControl = refreshControl        refreshControl.addTarget(self, action: #selector(refresh), for: UIControlEvents.valueChanged)        // 将UIRefreshControl添加到UIScrollView上        scrollView.refreshControl = refreshControl    }    func refresh() {        print("刷新事件执行了")        // 2秒后结束刷新        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 2) {            self.scrollView?.refreshControl?.endRefreshing()        }    }}