国家在Swiftui

Question

struct BasicView: View {
  @State var webView: WebView? = nil
  var body: some View {
    NavigationView {
      VStack {
        WebView(url: "myurl here") { view in
          print("setView called. Setting webView")
          self.webView = view
        }
      }
      .navigationTitle("My App")
      .navigationBarTitleDisplayMode(.inline)
      .navigationBarItems(
        leading: 
          Button(action: { 
            guard let view = webView else {
              print("webView not set")
              return
            }
            view.goBack()
          }) {
            Text("Back")
          }
        )
      }
    }
  }
}

现在在我的Webview中...

struct WebView: UIViewRepresentable {
  let url: URL
  let setParent: (WebView) -> Void

  var webView: WKWebView

  init(
    url: URL, 
    setParent: @ecaping (WebView) -> Void = {_ in },
    webView: WKWebView = WKWebView()
  )

  func makeCoordinator() -> Coordinator {
    Coordinator(self)
  }

  func makeUIView(context: Context) -> some WKWebView {
    webView.navigationDelegate = context.coordinator
    webView.uiDelegate = context.coordinator
    webView.load(URLRequest(url: url))
    setParent(self)
    return webView
  }

  func updateUIView(_ uiView: UIViewType, context: Context) {
  }

  func goBack() {
    //logic for going back
  }
  
  class Coordinator: NSObject, WKNavigationDelegate, WKUIDelegate {
    var parent: WebView
    
    init(_ parent: WebView) {
      self.parent = parent
    }
    //all my override functions for navigation and whatnot here
  }
}

，现在，当我运行我的应用程序时，我确实会在“ setView nater”。设置webview中看到，然后如果我单击导航栏中的后面按钮，我会看到“ webview not set set”

因此，要调用setparent，应该设置

self.webView

，因为该方法被调用了，但是当我单击导航栏中的按钮时，我会看到

webView not set

显示。因此，当调用SetParent时，状态变量以某种方式不会更新。

这是我第一次看到状态变量未更新并可用。我该如何继续？

使用

NavigationLink

以实现您问的东西

...to allow the webview to go "back" meaning the webview loads to a specific URL

。

Answer 1

工作示例测试代码：

import Foundation
import SwiftUI
import WebKit

struct ContentView: View {
    var body: some View {
        BasicView()
    }
}

struct BasicView: View {
    let swiftUIUrl = URL(string: "https://developer.apple.com/xcode/swiftui/")!
    
    let navStackUrl = URL(string: "https://developer.apple.com/documentation/swiftui/navigationstack/")!
    
    var body: some View {
        NavigationStack {
            VStack(spacing: 55) {
                NavigationLink(destination:  WebView(url: swiftUIUrl)) {
                    Text("Go to SwiftUI")
                }
                NavigationLink(destination:  WebView(url: navStackUrl)) {
                    Text("Go to NavigationStack")
                }
            }
            .navigationTitle("My App")
            .navigationBarTitleDisplayMode(.inline)
        }
    }
}

struct WebView: UIViewRepresentable {
    let url: URL

    func makeUIView(context: Context) -> WKWebView {
        let webView = WKWebView()
        return webView
    }
    
    func updateUIView(_ uiView: WKWebView, context: Context) {
        let request = URLRequest(url: url)
        uiView.load(request)
    }
}

其他工作示例代码使用数据模型：

// the data model
struct MyData: Identifiable {
    let id = UUID()
    var url: URL?
    var name: String
}

struct BasicView: View {
    // the data
    let urls = [
        MyData(url: URL(string: "https://developer.apple.com/xcode/swiftui/"), name: "SwiftUI"),
        MyData(url: URL(string: "https://developer.apple.com/documentation/swiftui/navigationstack/"), name: "NavigationStack")
    ]
    
    var body: some View {
        NavigationStack {
            List(urls) { data in
                NavigationLink(destination:  WebView(url: data.url)) {
                    Text("Go to \(data.name)")
                }
            }
            .navigationTitle("My App")
            .navigationBarTitleDisplayMode(.inline)
        }
    }
}

struct WebView: UIViewRepresentable {
    let url: URL?

    func makeUIView(context: Context) -> WKWebView {
        let webView = WKWebView()
        return webView
    }
    
    func updateUIView(_ uiView: WKWebView, context: Context) {
        if let url {
            let request = URLRequest(url: url)
            uiView.load(request)
        }
    }
}