SwiftUI 中級之下拉更新PullRefresh （2020年教程）

將之前等代碼封裝成struct

import SwiftUI

public struct PullToRefresh: UIViewRepresentable {
    
    let action: () -> Void
    @Binding var isShowing: Bool
    
    public init(
        action: @escaping () -> Void,
        isShowing: Binding<Bool>
    ) {
        self.action = action
        _isShowing = isShowing
    }
    
    public class Coordinator {
        let action: () -> Void
        let isShowing: Binding<Bool>
        
        init(
            action: @escaping () -> Void,
            isShowing: Binding<Bool>
        ) {
            self.action = action
            self.isShowing = isShowing
        }
        
        @objc
        func onValueChanged() {
            isShowing.wrappedValue = true
            action()
        }
    }
    
    public func makeUIView(context: UIViewRepresentableContext<PullToRefresh>) -> UIView {
        return UIView(frame: .zero)
    }
    
    private func tableView(root: UIView) -> UITableView? {
        for subview in root.subviews {
            if let tableView = subview as? UITableView {
                return tableView
            } else if let tableView = tableView(root: subview) {
                return tableView
            }
        }
        return nil
    }

    public func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<PullToRefresh>) {
        
        DispatchQueue.main.asyncAfter(deadline: .now()) {
            guard let viewHost = uiView.superview?.superview else {
                return
            }
            guard let tableView = self.tableView(root: viewHost) else {
                return
            }
            
            if let refreshControl = tableView.refreshControl {
                if self.isShowing {
                    refreshControl.beginRefreshing()
                } else {
                    refreshControl.endRefreshing()
                }
                return
            }
            
            let refreshControl = UIRefreshControl()
            refreshControl.addTarget(context.coordinator, action: #selector(Coordinator.onValueChanged), for: .valueChanged)
            tableView.refreshControl = refreshControl
        }
    }
    
    public func makeCoordinator() -> Coordinator {
        return Coordinator(action: action, isShowing: $isShowing)
    }
}

做個下拉更新時間等demo

import SwiftUI

struct TimePullRefreshView: View {
     @State var isShowing: Bool = false
       @State var array = ["date"]
       var body: some View {
          NavigationView {
            List(array, id: \.self) { text in
              Text(text)
            }
            .navigationBarTitle("刷新時間")
          }
          .background(PullToRefresh(action: {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
              self.isShowing = false
              //self.array.append(Date().description)
               self.array.insert(Date().description, at: 0)
            }
          }, isShowing: $isShowing))
        }
}

struct TimePullRefreshView_Previews: PreviewProvider {
    static var previews: some View {
        TimePullRefreshView()
    }
}

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