iOS 14 引入了一种新方法来接收 javascript 调用并使用 WKScriptMessageHandlerWithReply 而不是 WKScriptMessageHandler（在 WebKit 视图内）提供响应。然而文档基本上不存在。这是如何运作的？
1 回答
侃侃无极
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我对此进行了深入研究，发现它使用 Javascript Promises 来提供回调机制（并且从应用程序代码返回到 javascript 的响应必须是异步的）。
下面是一些示例代码来说明：
快速代码：
import UIKit
import WebKit
import PureLayout
final class ViewController: UIViewController {
var webView : WKWebView?
let JavaScriptAPIObjectName = "namespaceWithinTheInjectedJSCode"
override func viewDidLoad() {
super.viewDidLoad()
//-------
guard let scriptPath = Bundle.main.path(forResource: "script", ofType: "js"),
let scriptSource = try? String(contentsOfFile: scriptPath) else { return }
let userScript = WKUserScript(source: scriptSource, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
let config = WKWebViewConfiguration()
let userContentController = WKUserContentController()
userContentController.addUserScript(userScript)
// REQUIRES IOS14
if #available(iOS 14, *){
userContentController.addScriptMessageHandler(self, contentWorld: .page, name: JavaScriptAPIObjectName)
}
config.userContentController = userContentController
webView = WKWebView(frame: .zero, configuration: config)
if let webView = webView{
view.addSubview(webView)
webView.autoPinEdgesToSuperviewMargins() // using PureLayout for easy AutoLayout syntax
if let htmlPath = Bundle.main.url(forResource: "page", withExtension: "html"){
webView.loadFileURL( htmlPath, allowingReadAccessTo: htmlPath);
}
}
}
// need to deinit and remove webview stuff
deinit {
if let webView = webView{
let ucc = webView.configuration.userContentController
ucc.removeAllUserScripts()
ucc.removeScriptMessageHandler(forName:JavaScriptAPIObjectName)
}
}
}
extension ViewController: WKScriptMessageHandlerWithReply {
func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage, replyHandler: @escaping (Any?, String?) -> Void) {
if message.name == JavaScriptAPIObjectName, let messageBody = message.body as? String {
print(messageBody)
replyHandler( 2.2, nil ) // first var is success return val, second is err string if error
}
}
}
这是通过 Swift 代码加载并注入到网页中的 script.js：
function sampleMethodTheHTMLCanCall( inputInfo, successFunc, errorFunc ) {
var promise = window.webkit.messageHandlers.namespaceWithinTheInjectedJSCode.postMessage( inputInfo );
promise.then(
function(result) {
console.log(result); // "Stuff worked!"
successFunc( result )
},
function(err) {
console.log(err); // Error: "It broke"
errorFunc( err )
});
}
这是可以调用应用程序代码的 page.html 示例 HTML：
<html>
<meta name="viewport" content="width=device-width" />
<script>
function handleInfoFromApp( fromApp ){
document.getElementById("valToWrite").innerHTML = fromApp;
}
function handleError( err ){
}
</script>
<h1 id="valToWrite">Hello</h1>
<button onclick="sampleMethodTheHTMLCanCall( 'inputInfo', handleInfoFromApp, handleError )">Load Info from App</button>
</html>
上面的 HTML 提供了稍后在 javascript 发起的请求成功或失败时由应用程序扩展代码调用的函数。
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