从 WKWebView 中的本机代码调用 JavaScript 函数

Question

在 iOS 8 中使用 WKWebView，我如何从本机端运行 JavaScript 函数或以其他方式从本机端与 JavaScript 通信？似乎没有类似于 UIWebView 的stringByEvaluatingJavaScriptFromString: 的方法。

（我可以在configuration.userContentController 对象上使用- addScriptMessageHandler:name: 来允许从JS 到本机的通信，但我正在寻找相反的方向。）

Answer 1

（我在这里提出问题后不久就为此提交了雷达。）

前几天刚刚添加了一个新方法（感谢jcesarmobile指出）：

添加-[WKWebView evaluateJavaScript:completionHandler:]
http://trac.webkit.org/changeset/169765

该方法适用于 iOS 8 beta 3 及更高版本。这是新的方法签名：

/* @abstract Evaluates the given JavaScript string. 
 @param javaScriptString The JavaScript string to evaluate. 
 @param completionHandler A block to invoke when script evaluation completes
     or fails. 
 @discussion The completionHandler is passed the result of the script evaluation
     or an error. 
*/ 
- (void)evaluateJavaScript:(NSString *)javaScriptString
         completionHandler:(void (^)(id, NSError *))completionHandler; 

文档可在此处获得：https://developer.apple.com/documentation/webkit/wkwebview/1415017-evaluatejavascript。

Answer 2

详情

• Xcode 9.1，Swift 4
• Xcode 10.2 (10E125)、Swift 5

说明

脚本被插入到将在 WKWebView 中显示的页面中。此脚本将返回页面 URL（但您可以编写另一个 JavaScript 代码）。这意味着脚本事件是在网页上生成的，但它会在我们的函数中处理：

func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {...}

解决方案

extension WKUserScript {
    enum Defined: String {
        case getUrlAtDocumentStartScript = "GetUrlAtDocumentStart"
        case getUrlAtDocumentEndScript = "GetUrlAtDocumentEnd"

        var name: String { return rawValue }

        private var injectionTime: WKUserScriptInjectionTime {
            switch self {
                case .getUrlAtDocumentStartScript: return .atDocumentStart
                case .getUrlAtDocumentEndScript: return .atDocumentEnd
            }
        }

        private var forMainFrameOnly: Bool {
            switch self {
                case .getUrlAtDocumentStartScript: return false
                case .getUrlAtDocumentEndScript: return false
            }
        }

        private var source: String {
            switch self {
            case .getUrlAtDocumentEndScript, .getUrlAtDocumentStartScript:
                return "webkit.messageHandlers.\(name).postMessage(document.URL)"
            }
        }

        fileprivate func create() -> WKUserScript {
            return WKUserScript(source: source,
                                injectionTime: injectionTime,
                                forMainFrameOnly: forMainFrameOnly)
        }
    }
}

extension WKWebViewConfiguration {
    func add(script: WKUserScript.Defined, scriptMessageHandler: WKScriptMessageHandler) {
        userContentController.addUserScript(script.create())
        userContentController.add(scriptMessageHandler, name: script.name)
    }
}

用法

初始化 WKWebView

 let config = WKWebViewConfiguration()
 config.add(script: .getUrlAtDocumentStartScript, scriptMessageHandler: self)
 config.add(script: .getUrlAtDocumentEndScript, scriptMessageHandler: self)

 webView = WKWebView(frame:  UIScreen.main.bounds, configuration: config)
 webView.navigationDelegate = self
 view.addSubview(webView)

捕捉事件

extension ViewController: WKScriptMessageHandler {
    func userContentController (_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if  let script = WKUserScript.Defined(rawValue: message.name),
            let url = message.webView?.url {
                switch script {
                    case .getUrlAtDocumentStartScript: print("start: \(url)")
                    case .getUrlAtDocumentEndScript: print("end: \(url)")
                }
        }
    }
}

完整代码示例

import UIKit
import WebKit

class ViewController: UIViewController, WKNavigationDelegate {

    private var webView = WKWebView()

    override func viewDidLoad() {
        super.viewDidLoad()

        let config = WKWebViewConfiguration()
        config.add(script: .getUrlAtDocumentStartScript, scriptMessageHandler: self)
        config.add(script: .getUrlAtDocumentEndScript, scriptMessageHandler: self)

        webView = WKWebView(frame:  UIScreen.main.bounds, configuration: config)
        webView.navigationDelegate = self
        view.addSubview(webView)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        webView.load(urlString: "http://apple.com")
    }
}

extension ViewController: WKScriptMessageHandler {
    func userContentController (_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if  let script = WKUserScript.Defined(rawValue: message.name),
            let url = message.webView?.url {
                switch script {
                    case .getUrlAtDocumentStartScript: print("start: \(url)")
                    case .getUrlAtDocumentEndScript: print("end: \(url)")
                }
        }
    }
}

extension WKWebView {
    func load(urlString: String) {
        if let url = URL(string: urlString) {
            load(URLRequest(url: url))
        }
    }
}

extension WKUserScript {
    enum Defined: String {
        case getUrlAtDocumentStartScript = "GetUrlAtDocumentStart"
        case getUrlAtDocumentEndScript = "GetUrlAtDocumentEnd"

        var name: String { return rawValue }

        private var injectionTime: WKUserScriptInjectionTime {
            switch self {
                case .getUrlAtDocumentStartScript: return .atDocumentStart
                case .getUrlAtDocumentEndScript: return .atDocumentEnd
            }
        }

        private var forMainFrameOnly: Bool {
            switch self {
                case .getUrlAtDocumentStartScript: return false
                case .getUrlAtDocumentEndScript: return false
            }
        }

        private var source: String {
            switch self {
            case .getUrlAtDocumentEndScript, .getUrlAtDocumentStartScript:
                return "webkit.messageHandlers.\(name).postMessage(document.URL)"
            }
        }

        fileprivate func create() -> WKUserScript {
            return WKUserScript(source: source,
                                injectionTime: injectionTime,
                                forMainFrameOnly: forMainFrameOnly)
        }
    }
}

extension WKWebViewConfiguration {
    func add(script: WKUserScript.Defined, scriptMessageHandler: WKScriptMessageHandler) {
        userContentController.addUserScript(script.create())
        userContentController.add(scriptMessageHandler, name: script.name)
    }
}

Info.plist

添加 Info.plist 传输安全设置

<key>NSAppTransportSecurity</key>
<dict>
    <key>NSAllowsArbitraryLoads</key>
    <true/>
</dict>

结果

资源

Document Object Properties and Methods

Answer 3

这可能不是一个理想的方法，但根据您的用例，您可以在感染用户脚本后重新加载 WKWebView：

NSString *scriptSource = @"alert('WKWebView JS Call!')";

WKUserScript *userScript = [[WKUserScript alloc] initWithSource:scriptSource
                                                  injectionTime:WKUserScriptInjectionTimeAtDocumentEnd
                                               forMainFrameOnly:YES];

[wkWebView.configuration.userContentController addUserScript:userScript];
[wkWebView reload];

Answer 4

这对我有用：

在定义“runJavaScriptInMainFrame:”方法的 WKWebView 上创建一个扩展。在扩展方法中，使用 NSInvocationOperation 调用未记录的 '_runJavaScriptInMainFrame:' 方法。

extension WKWebView {
    func runJavaScriptInMainFrame(#scriptString: NSString) -> Void {
        let selector : Selector = "_runJavaScriptInMainFrame:"
        let invocation = NSInvocationOperation(target: self, selector: selector, object: scriptString)
        NSOperationQueue.mainQueue().addOperation(invocation)
    }
}

要使用，请致电：

webview.runJavacriptInMainFrame:(scriptString: "some javascript code")

感谢 Larsaronen 提供 WKWebView 私有 API 的链接。

Answer 5

我自己刚开始研究 WKWebView API，所以这可能不是最好的方法，但我认为您可以使用以下代码来实现：

NSString *scriptSource = @"console.log('Hi this is in JavaScript');";

WKUserScript *userScript = [[WKUserScript alloc]
    initWithSource:scriptSource
    injectionTime:WKUserScriptInjectionTimeAtDocumentStart 
    forMainFrameOnly:YES];

[myWKController addUserScript:userScript];

（来自 WWDC'14 演讲）

Answer 6

有传言说这是一个错误，因为有一个类似于 UIWebView 中公开可用的私有函数（？），用于从 obj-C 评估 javascript。

Answer 7

方法示例，运行 JS 代码从 base64String 加载 .pdf

  private func setData(_ base64String: String) {
    webView.evaluateJavaScript(
        "externalInterfaceLoadBase64('\(base64String)', scale = 1.0)",
        completionHandler: { _, error in
            if let error = error {
                debugPrint("Evaluating JavaScript error: \(error)")
            }
        }
    )
}