ScrollView中使用Delegate 滚动 UIKit的UIScrollView转化为在SwiftUI中使用

2019年8月26日

用SWiftUI的ScrollView设计界面，发现该控件没有实现Delegate系列回掉接口，因此需要将UIKit中的UIScrollView继承到SwiftUI的View上面来显示，最简单的转化代码如下所示：

 

import SwiftUI
import UIKit
// in swiftui view file, use like this, it will contruct a scroll view
//LegacyScrollView()

struct LegacyScrollView : UIViewRepresentable {
    // any data state, like @State/@Binding/etc, if needed
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    func makeUIView(context: Context) -> UIScrollView {
        let control = UIScrollView()
        control.refreshControl = UIRefreshControl()
        control.refreshControl?.addTarget(context.coordinator, action:
            #selector(Coordinator.handleRefreshControl),
                                          for: .valueChanged)

        control.delegate = context.coordinator
        
        // Simply to give some content to see in the app
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 30))
        label.text = "Scroll View Content"
        control.addSubview(label)

        return control
    }
    func updateUIView(_ uiView: UIScrollView, context: Context) {
        // code to update scroll view from view state, if needed
    }

    class Coordinator: NSObject, UIScrollViewDelegate{
        var control: LegacyScrollView

        init(_ control: LegacyScrollView) {
            self.control = control
        }
        @objc func handleRefreshControl(sender: UIRefreshControl) {
            // handle the refresh event
            sender.endRefreshing()
        }
        @objc func scrollViewWillBeginDragging(_ scrollView: UIScrollView){
        }
        @objc func scrollViewDidScroll(_ scrollView: UIScrollView){
        }
    }
}