WKWebView evaluateJavaScript 未返回 html

Question

我正在尝试使用 evaluateJavaScript 解析从 WKWebView load() 返回的 html，但它从不打印任何内容。我这样做对吗？还有其他办法吗？ didFinish 确实打印。

import UIKit
import WebKit

class MyWebViewController: UIViewController, WKNavigationDelegate {

var webView: WKWebView!

override func viewDidLoad() {
    super.viewDidLoad()

    webView = WKWebView(frame:  self.view.frame)
    webView.navigationDelegate = self

    let url = NSURL (string: "https://google.com");
    let request = NSURLRequest(url: url! as URL)
    webView.load(request as URLRequest)

    self.view.addSubview(webView)

    self.view.sendSubview(toBack: webView)

}


func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {

    webView.evaluateJavaScript("document.documentElement.outerHTML.toString()", completionHandler: { (html: AnyObject?, error: NSError?) in
        print(html!)
        } as? (Any?, Error?) -> Void)

    print("didFinish")

}

}

Answer 1

将 evaluateJavaScript 与 WKWebView 一起使用有点棘手。

因为我认为这个答案对很多人都有用，而不是用一个简短的代码片段和一个你需要实现的评论来解决你的具体问题 WKScriptMessageHandler，我将 post 一个完整的示例，您可以使用它来了解一切如何协同工作。

要使用它，请在 Xcode 中创建一个 "Single View Application" iOS 项目并将其粘贴到默认的 ViewController.swift 文件中。

//
//  WebViewController.swift
//  WKWebViewExample
//
//  Created by par on 4/2/17.
//  Copyright © 2017 par. All rights reserved.  MIT License.
//

import UIKit
import WebKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        let webViewController = WebViewController()

        // install the WebViewController as a child view controller
        addChildViewController(webViewController)

        let webViewControllerView = webViewController.view!

        view.addSubview(webViewControllerView)

        webViewControllerView.translatesAutoresizingMaskIntoConstraints = false
        webViewControllerView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        webViewControllerView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        webViewControllerView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        webViewControllerView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true

        webViewController.didMove(toParentViewController: self)
    }
}

class WebViewController: UIViewController, WKNavigationDelegate, WKScriptMessageHandler {
    private var webView: WKWebView!
    private var webViewContentIsLoaded = false

    init() {
        super.init(nibName: nil, bundle: nil)

        self.webView = {
            let contentController = WKUserContentController()

            contentController.add(self, name: "WebViewControllerMessageHandler")

            let configuration = WKWebViewConfiguration()
            configuration.userContentController = contentController

            let webView = WKWebView(frame: .zero, configuration: configuration)
            webView.scrollView.bounces = false
            webView.navigationDelegate = self

            return webView
        }()
    }

    required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(webView)

        webView.translatesAutoresizingMaskIntoConstraints = false
        webView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        webView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        webView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        webView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        if !webViewContentIsLoaded {
            let url = URL(string: "https://whosebug.com")!
            let request = URLRequest(url: url)

            webView.load(request)

            webViewContentIsLoaded = true
        }
    }

    private func evaluateJavascript(_ javascript: String, sourceURL: String? = nil, completion: ((_ error: String?) -> Void)? = nil) {
        var javascript = javascript

        // Adding a sourceURL comment makes the javascript source visible when debugging the simulator via Safari in Mac OS
        if let sourceURL = sourceURL {
            javascript = "//# sourceURL=\(sourceURL).js\n" + javascript
        }

        webView.evaluateJavaScript(javascript) { _, error in
            completion?(error?.localizedDescription)
        }
    }

    // MARK: - WKNavigationDelegate

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        // This must be valid javascript!  Critically don't forget to terminate statements with either a newline or semicolon! 
        let javascript =
            "var outerHTML = document.documentElement.outerHTML.toString()\n" +
            "var message = {\"type\": \"outerHTML\", \"outerHTML\": outerHTML }\n" +
            "window.webkit.messageHandlers.WebViewControllerMessageHandler.postMessage(message)\n"

        evaluateJavascript(javascript, sourceURL: "getOuterHMTL")
    }

    // MARK: - WKScriptMessageHandler

    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        guard let body = message.body as? [String: Any] else {
            print("could not convert message body to dictionary: \(message.body)")
            return
        }

        guard let type = body["type"] as? String else {
            print("could not convert body[\"type\"] to string: \(body)")
            return
        }

        switch type {
        case "outerHTML":
            guard let outerHTML = body["outerHTML"] as? String else {
                print("could not convert body[\"outerHTML\"] to string: \(body)")
                return
            }
            print("outerHTML is \(outerHTML)")
        default:
            print("unknown message type \(type)")
            return
        }
    }
}

Answer 2

我知道自从回答这个问题已经有一段时间了，我发现这对我来说并不奏效。我用下面的代替。

在添加 setTimeout() 函数之前，我无法让 evaluateJavaScript 工作。下面是我的代码。

webView.evaluateJavaScript("setTimeout(function(){ 
// Do something here
},10);") { (result1, error) in
            if error == nil {
                print(result1 ?? "")
            }
        }

WKWebView evaluateJavaScript 未返回 html

WKWebView evaluateJavaScript not returning html

ios

swift

wkwebview