直接从WKWebView获取已加载的PDF，而无需再次下载

Question

我试图直接将PDF加载到WKWebView中，而不向URL发出另一个直接请求。

在研究期间，我遇到了以下链接，该链接具有相同的作用。 IOS - How to get cached resources from WKWebView?

但是用这种方法，我在某些URL中遇到了问题。 我在控制台中遇到Javascript错误 Blocked script execution in 'https://ac.els-cdn.com/S0946672X17308763/1-s2.0-S0946672X17308763-main.pdf?_tid=8d087878-4e4c-4c50-b5e4-08ea38906e6e&download=true&acdnat=1534405212_984aaf5f9673f1b2ff107a4032c80ea0' because the document's frame is sandboxed and the 'allow-scripts' permission is not set.

用于重现该问题的URL。 https://www.sciencedirect.com/science/article/pii/S0946672X17308763 只需访问“下载PDF”链接，然后在WKWebView中打开PDF。

编辑，用于在同一WebView中轻松加载新的Tab窗口。

-(WKWebView *)webView:(WKWebView *)webView createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration forNavigationAction:(WKNavigationAction *)navigationAction windowFeatures:(WKWindowFeatures *)windowFeatures{

    if (!navigationAction.targetFrame.isMainFrame) {
        [_webView loadRequest:navigationAction.request];
    }
    return nil;
}

编辑

我正在添加由@SahilManchanda提供的解决方案派生的完整快速代码，但是在代码片段中添加链接仍然存在一些问题。

import UIKit
import WebKit

class ViewController: UIViewController {

    var webView: WKWebView!
    var button: UIButton!
    let link = "https://www.sciencedirect.com/science/article/pii/S0946672X17308763"

    var activityIndicator: UIActivityIndicatorView?
    override func viewDidLoad() {
        super.viewDidLoad()

    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        webView = WKWebView()
        button = UIButton()
        button.setTitle("Save", for: .normal)
        button.setTitleColor(.white, for: .normal)
        button.backgroundColor = UIColor.black.withAlphaComponent(0.5)
        button.addTarget(self, action: #selector(self.download(_:)), for: .touchUpInside)
        activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
        webView.navigationDelegate = self
        webView.uiDelegate = self
        activityIndicator?.center = self.view.center
        [webView,button].forEach({view.addSubview($0)})
        setupConstraints()
        webView.configuration.userContentController.add(self, name: "myInterface")
        webView.load(URLRequest(url: URL(string: link)!))
        activityIndicator?.startAnimating()
    }

    func setupConstraints(){
        webView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            webView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            webView.topAnchor.constraint(equalTo: view.topAnchor),
            webView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            webView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
            ])
        button.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            button.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -70),
            button.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
            button.widthAnchor.constraint(equalToConstant: 100)
            ])
    }
    @objc func download(_ sender: Any){

        let s = """
        var xhr = new XMLHttpRequest();
        xhr.open('GET', "\(webView.url!.absoluteString)", true);
        xhr.responseType = 'arraybuffer';
        xhr.onload = function(e) {
        if (this.status == 200) {
        var uInt8Array = new Uint8Array(this.response);
        var i = uInt8Array.length;
        var binaryString = new Array(i);
        while (i--){
        binaryString[i] = String.fromCharCode(uInt8Array[i]);
        }
        var data = binaryString.join('');
        var base64 = window.btoa(data);

        window.webkit.messageHandlers.myInterface.postMessage(base64);
        }
        };
        xhr.send();
        """
        webView?.evaluateJavaScript(s, completionHandler: {(string,error) in
            print(error ?? "no error")
        })
    }
}
extension ViewController: WKScriptMessageHandler{
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        guard
            var documentsURL = (FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)).last,
            let convertedData = Data.init(base64Encoded: message.body as! String)
            else {
                //handle error when getting documents URL
                return
        }
        //name your file however you prefer
        documentsURL.appendPathComponent("sample.pdf")
        do {
            try convertedData.write(to: documentsURL)
        } catch {
            //handle write error here
        }
        //if you want to get a quick output of where your
        //file was saved from the simulator on your machine
        //just print the documentsURL and go there in Finder
        print("URL for view \(documentsURL.absoluteString)")
        let activityViewController = UIActivityViewController.init(activityItems: [documentsURL], applicationActivities: nil)
        present(activityViewController, animated: true, completion: nil)
    }
}

extension ViewController: WKNavigationDelegate,WKUIDelegate{

    func webView(_ webView: WKWebView, createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView? {

        if !(navigationAction.targetFrame != nil && (navigationAction.targetFrame?.isMainFrame)!){
            webView .load(navigationAction.request);
        }

        return nil
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        self.activityIndicator?.stopAnimating()
        self.activityIndicator?.removeFromSuperview()
        self.activityIndicator = nil
    }
}

Answer 1

尝试在模拟器上执行以下代码。直接pdf链接不可用。它们动态生成pdf链接。因此，当页面加载完成时，它将具有最近的URL，并再次调用download方法，因此它将从缓存中保存。

   import UIKit
import WebKit

class ViewController: UIViewController {

    var webView: WKWebView!
    var newWebView: WKWebView?
    let link = "https://www.sciencedirect.com/science/article/pii/S0946672X17308763"
    var d = false
    var activityIndicator: UIActivityIndicatorView?
    override func viewDidLoad() {
        super.viewDidLoad()

    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        webView = WKWebView()
        activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
        webView.navigationDelegate = self
        webView.uiDelegate = self
        activityIndicator?.center = self.view.center
        [webView].forEach({view.addSubview($0)})
        setupConstraints()
        webView.configuration.userContentController.add(self, name: "myInterface")
        webView.load(URLRequest(url: URL(string: link)!))
        activityIndicator?.startAnimating()
    }

    func setupConstraints(){
        webView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            webView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            webView.topAnchor.constraint(equalTo: view.topAnchor),
            webView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            webView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
            ])
    }
    func download(_ sender: Any){
        guard let link = (sender as? URL)?.absoluteString else {return}
        print("\(link)")
        let s = """
        var xhr = new XMLHttpRequest();
        xhr.open('GET', "\(link)", true);
        xhr.responseType = 'arraybuffer';
        xhr.onload = function(e) {
        if (this.status == 200) {
        var uInt8Array = new Uint8Array(this.response);
        var i = uInt8Array.length;
        var binaryString = new Array(i);
        while (i--){
        binaryString[i] = String.fromCharCode(uInt8Array[i]);
        }
        var data = binaryString.join('');
        var base64 = window.btoa(data);

        window.webkit.messageHandlers.myInterface.postMessage(base64);
        }
        };
        xhr.send();
        """
        webView?.evaluateJavaScript(s, completionHandler: {(string,error) in
            print(error ?? "no error")
        })
    }
}
extension ViewController: WKScriptMessageHandler{
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        guard
            var documentsURL = (FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)).last,
            let convertedData = Data.init(base64Encoded: message.body as! String)
            else {
                //handle error when getting documents URL
                return
        }
        //name your file however you prefer
        documentsURL.appendPathComponent("sample.pdf")
        do {
            try convertedData.write(to: documentsURL)
        } catch {
            //handle write error here
        }
        //if you want to get a quick output of where your
        //file was saved from the simulator on your machine
        //just print the documentsURL and go there in Finder
        print("URL for view \(documentsURL.absoluteString)")
        let activityViewController = UIActivityViewController.init(activityItems: [documentsURL], applicationActivities: nil)
        present(activityViewController, animated: true, completion: nil)
    }
}

extension ViewController: WKNavigationDelegate,WKUIDelegate{

    func webView(_ webView: WKWebView, createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView? {

        if !(navigationAction.targetFrame != nil && (navigationAction.targetFrame?.isMainFrame)!){
            webView .load(navigationAction.request);

        }

        return nil
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        self.activityIndicator?.stopAnimating()
        self.activityIndicator?.removeFromSuperview()
        self.activityIndicator = nil
        if d{
            download(webView.url)
        }
    }
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        print("url \(navigationAction.request.url!.absoluteString)")
        if navigationAction.request.url!.absoluteString.contains("pdfft"){
            if !d{
                d = true
                let url = navigationAction.request.url?.absoluteString.components(separatedBy: "?").first ?? ""
                decisionHandler(.cancel)
                webView.load(URLRequest(url: URL(string: url)!))
                return
            }

        }
        decisionHandler(.allow)
    }
}

页面加载完成后。点击保存按钮。然后应打印如下内容：

  

查看网址   文件：///Users/jingged/Library/Developer/CoreSimulator/Devices/B57CEFE8-2A2A-484B-AB36-58E05B68EB1A/data/Containers/Data/Application/17317462-D36C-40EA-AEBD-0F128DC7E66A/Documents/sample.pdf

复制网址并粘贴到任何浏览器中。