SwiftUI：不要刷新自定义视图 MacOS 应用程序

Question

Hello I want to create an application with several webview that once they have been loaded once, I don't want them to be recreated anymore I want them to keep their instance.

I create in my application A navigation view which includes a list of 10 sites. When I click on a item of the list I want to display the corresponding webview with NavigationLink. It works. But the problem is that if I click on another item of the list and I will return to the previous one it returns to the home page, the webview loads again. I want the webview to be created only once and always stay alive in as long as the app is alive. I know that swiftui always refresh views is the problem, how can I prevent my webview from being refreshed by swiftUI?

In uitkit it's simple I create an array of wkwebview at launch of the app, I load all my webview url, in a singleton class. And depending on the item selected from my tableview I display the corresponding wkwebview. And even if I change the item all my webview are alive even if we don't see them.

struct WebView : UIViewRepresentable {

    let request: URLRequest

    func makeUIView(context: Context) -> WKWebView  {
        let web = WKWebView()
        web.load(request)
        return web
    }

    func updateUIView(_ uiView: WKWebView, context: Context) {

    }

}

Answer 1

Here is simplified demo of possible approach. The idea is to cache created WKWebView objects by some identifiers and just reuse them in created (or recreated) thin-wrapper SwiftUI view representable.

Tested & works with Xcode 11.2 / iOS 13.2

struct WebView: UIViewRepresentable {

    private static var cache: [Int: WKWebView] = [:]

    // the only allowed entry point to create WebView, so have control either
    // to create new instance of WKWebView or provide already loaded
    static func view(with id: Int, request: URLRequest) -> WebView {
        var web = cache[id] // it is UI thread so safe to access static
        if web == nil {
            web = WKWebView()
            cache[id] = web
        }
        return WebView(with: web!, request: request)
    }

    private init(with web: WKWebView, request: URLRequest) {
        self.web = web
        self.request = request
    }

    private let web: WKWebView
    private let request: URLRequest

    func makeUIView(context: Context) -> WKWebView  {
        if web.url == nil { // just created, so perform initial loading
            web.load(request)
        }
        return web
    }

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

// Just simple test view
struct TestOnceLoadedWebView: View {
    private let urls: [String] = [
        "http://www.apple.com",
        "http://www.google.com",
        "http://www.amazon.com"
    ]

    var body: some View {
        NavigationView {
            List(0 ..< urls.count) { i in
                NavigationLink("Link \(i)", destination:
                    WebView.view(with: i, request: 
                                 URLRequest(url: URL(string: self.urls[i])!)))
            }
        }
    }
}