ios webView与js交互与类似回调的实现（swift）

直接代码，首先加载一个webView：

        webView = UIWebView.init(frame: CGRect(x: 0, y: 0, width: self.view.frame.size.width, height: self.view.frame.size.height))
        webView.delegate = self
        webView.loadRequest(NSURLRequest(URL: NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("File", ofType: "html")!)))//本地文件测试
        webView.scrollView.delegate = self
        webView.scrollView.tag = 1
        view.addSubview(webView)

实现方法：

 func webViewDidStartLoad(webView: UIWebView) {
//        print("开始加载")
//        webView.stringByEvaluatingJavaScriptFromString("        document.write(Date());")//与js的交互通过这个方法可以在网页中相当于加入一段js代码
//    webView.stringByEvaluatingJavaScriptFromString("document.getElementById('demo').innerHTML = '段落已修改'")
    }
    //
    func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        if navigationType == .LinkClicked {
            print("LinkClicked")
            
//            let uid = webView.stringByEvaluatingJavaScriptFromString("method();")
//            print("uid = \(uid!)")
            
//            if request.URL?.absoluteString == "http://www.baidu.com/"  {
//                let secView = WebViewController()
//                secView.webView.loadRequest(request)
//                self.navigationController?.pushViewController(secView, animated: true)
//            }
//            if request.URL?.absoluteString == "http://www.google.com/"  {
//                let secView = WebViewController()
//                secView.webView.loadRequest(request)
//                self.navigationController?.pushViewController(secView, animated: true)
//            }
            return false
        }
        if navigationType == .BackForward {
            
        }
        if navigationType == .Other {
            
        }
        if navigationType == .FormSubmitted {
            print("FormSubmitted")
           
        }
        return true
    }
    
    func webView(webView: UIWebView, didFailLoadWithError error: NSError?) {
        if (error != nil) {
            kError = error
        }
        
    }
    
    func webViewDidFinishLoad(webView: UIWebView) {
//        print("jiazaijieshu")
//        let high = webView.stringByEvaluatingJavaScriptFromString("document.body.scrollHeight;")//此处运行js代码获取页面高度
//        print(high!)
        let jsContext = webView.valueForKeyPath("documentView.webView.mainFrame.javaScriptContext")//获取当前js运行环境
        let webBack: @convention(block) String -> () = { input in
            print(input)
//            return mutableString as String
            
        }//设置回调方法  （姑且这么称呼）
        //unsafeBitCast为类型转换将type @convention(block) Swift.String -> ()转换为AnyObject，且不会对这个操作进行检查，使用unsafeBitCast要<strong>确保两边类型正确</strong>，应该使用更安全的方法，目前没找到
        jsContext!.setObject(unsafeBitCast(webBack, AnyObject.self), forKeyedSubscript: "simplifyString")//在上下文中加入回调
    }
    
    func scrollViewDidScroll(scrollView: UIScrollView) {
//        if scrollView == webView.scrollView {
//            let y = webView.stringByEvaluatingJavaScriptFromString("window.pageYOffset")
//            print(y)
//        }

    }

上面回调的使用是在web的代码中，

 <p><a href="http://www.baidu.com/" id="BaiDu" onclick="theFunc(this)" >去百度</a>   是一个指向万维网上的页面的链接。</p>

<script>

function theFunc(obj) {

        webBack(obj.id)

    }

</script>