任何人都请告诉我如何在iOS wkwebview中下载文件。我创建了一个iOS Webview应用。在该页面中，我已经加载了它有多个下载选项，但是当我单击“下载”时，没有任何反应。
注意：我不想创建额外的按钮来下载
答案 0 :(得分：1)
如 Sayooj's link所暗示：
您必须自己处理下载业务
在WKWebView中完成下载任务后，您可以从方法func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void) {中获取要下载的文件URL
然后您启动下载任务以下载文件，URLSession是一个选择
下载后即可处理文件。上面的链接显示了如何使用QLPreviewController
import UIKit
import WebKit
class ViewController: UIViewController, WKUIDelegate, WKNavigationDelegate {
var webView: WKWebView!
var webViewCookieStore: WKHTTPCookieStore!
let webViewConfiguration = WKWebViewConfiguration()
override func viewDidLoad() {
super.viewDidLoad()
webView = WKWebView(frame: yourFrame, configuration: webViewConfiguration)
webView.uiDelegate = self
webView.navigationDelegate = self
view.addSubview(webView)
webView.load(URLRequest(url: yourUrlString))
}
/*
Needs to be intercepted here, because I need the suggestedFilename for download
*/
func webView(_ webView: WKWebView,
decidePolicyFor navigationResponse: WKNavigationResponse,
decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void) {
let url = navigationResponse.response.url
let documentUrl = url?.appendingPathComponent(navigationResponse.response.suggestedFilename!)
loadAndDisplayDocumentFrom(url: documentUrl!)
decisionHandler(.cancel)
}
/*
Download the file from the given url and store it locally in the app's temp folder.
*/
private func loadAndDisplayDocumentFrom(url downloadUrl : URL) {
let localFileURL = FileManager.default.temporaryDirectory.appendingPathComponent(downloadUrl.lastPathComponent)
URLSession.shared.dataTask(with: downloadUrl) { data, response, err in
guard let data = data, err == nil else {
debugPrint("Error while downloading document from url=\(downloadUrl.absoluteString): \(err.debugDescription)")
return
}
if let httpResponse = response as? HTTPURLResponse {
debugPrint("Download http status=\(httpResponse.statusCode)")
}
// write the downloaded data to a temporary folder
do {
try data.write(to: localFileURL, options: .atomic) // atomic option overwrites it if needed
debugPrint("Stored document from url=\(downloadUrl.absoluteString) in folder=\(localFileURL.absoluteString)")
DispatchQueue.main.async {
// localFileURL
// here is where your file
}
} catch {
debugPrint(error)
return
}
}.resume()
}
}
答案 1 :(得分：1)
Sayooj's link暗示，您还可以使用JavaScript下载文件。
当然，您将自己处理文件下载的代码。
使用func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {，您将获得要下载的文件URL。
然后使用JS下载。
如果成功，JS会调用下载的方法，系统会通过public func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {通知您，
然后您就可以处理下载的文件
有点复杂。使用JavaScript下载文件，使用WKScriptMessageHandler在本机Swift和JavaScript之间进行通信。
class ViewController: UIViewController, WKUIDelegate, WKNavigationDelegate, WKScriptMessageHandler {
var webView: WKWebView!
let webViewConfiguration = WKWebViewConfiguration()
override func viewDidLoad() {
super.viewDidLoad()
// init this view controller to receive JavaScript callbacks
webViewConfiguration.userContentController.add(self, name: "openDocument")
webViewConfiguration.userContentController.add(self, name: "jsError")
webView = WKWebView(frame: yourFrame, configuration: webViewConfiguration)
}
func webView(_ webView: WKWebView,
decidePolicyFor navigationAction: WKNavigationAction,
decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
let url = navigationAction.request.url
decisionHandler(.cancel)
executeDocumentDownloadScript(forAbsoluteUrl: url!.absoluteString)
}
/*
Handler method for JavaScript calls.
Receive JavaScript message with downloaded document
*/
public func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
debugPrint("did receive message \(message.name)")
if (message.name == "openDocument") {
handleDocument(messageBody: message.body as! String)
} else if (message.name == "jsError") {
debugPrint(message.body as! String)
}
}
/*
Open downloaded document in QuickLook preview
*/
private func handleDocument(messageBody: String) {
// messageBody is in the format ;data:;base64,
// split on the first ";", to reveal the filename
let filenameSplits = messageBody.split(separator: ";", maxSplits: 1, omittingEmptySubsequences: false)
let filename = String(filenameSplits[0])
// split the remaining part on the first ",", to reveal the base64 data
let dataSplits = filenameSplits[1].split(separator: ",", maxSplits: 1, omittingEmptySubsequences: false)
let data = Data(base64Encoded: String(dataSplits[1]))
if (data == nil) {
debugPrint("Could not construct data from base64")
return
}
// store the file on disk (.removingPercentEncoding removes possible URL encoded characters like "%20" for blank)
let localFileURL = FileManager.default.temporaryDirectory.appendingPathComponent(filename.removingPercentEncoding ?? filename)
do {
try data!.write(to: localFileURL);
} catch {
debugPrint(error)
return
}
// and display it in QL
DispatchQueue.main.async {
// localFileURL
// now you have your file
}
}
/*
Intercept the download of documents in webView, trigger the download in JavaScript and pass the binary file to JavaScript handler in Swift code
*/
private func executeDocumentDownloadScript(forAbsoluteUrl absoluteUrl : String) {
// TODO: Add more supported mime-types for missing content-disposition headers
webView.evaluateJavaScript("""
(async function download() {
const url = '\(absoluteUrl)';
try {
// we use a second try block here to have more detailed error information
// because of the nature of JS the outer try-catch doesn't know anything where the error happended
let res;
try {
res = await fetch(url, {
credentials: 'include'
});
} catch (err) {
window.webkit.messageHandlers.jsError.postMessage(`fetch threw, error: ${err}, url: ${url}`);
return;
}
if (!res.ok) {
window.webkit.messageHandlers.jsError.postMessage(`Response status was not ok, status: ${res.status}, url: ${url}`);
return;
}
const contentDisp = res.headers.get('content-disposition');
if (contentDisp) {
const match = contentDisp.match(/(^;|)\\s*filename=\\s*(\"([^\"]*)\"|([^;\\s]*))\\s*(;|$)/i);
if (match) {
filename = match[3] || match[4];
} else {
// TODO: we could here guess the filename from the mime-type (e.g. unnamed.pdf for pdfs, or unnamed.tiff for tiffs)
window.webkit.messageHandlers.jsError.postMessage(`content-disposition header could not be matched against regex, content-disposition: ${contentDisp} url: ${url}`);
}
} else {
window.webkit.messageHandlers.jsError.postMessage(`content-disposition header missing, url: ${url}`);
return;
}
if (!filename) {
const contentType = res.headers.get('content-type');
if (contentType) {
if (contentType.indexOf('application/json') === 0) {
filename = 'unnamed.pdf';
} else if (contentType.indexOf('image/tiff') === 0) {
filename = 'unnamed.tiff';
}
}
}
if (!filename) {
window.webkit.messageHandlers.jsError.postMessage(`Could not determine filename from content-disposition nor content-type, content-dispositon: ${contentDispositon}, content-type: ${contentType}, url: ${url}`);
}
let data;
try {
data = await res.blob();
} catch (err) {
window.webkit.messageHandlers.jsError.postMessage(`res.blob() threw, error: ${err}, url: ${url}`);
return;
}
const fr = new FileReader();
fr.onload = () => {
window.webkit.messageHandlers.openDocument.postMessage(`${filename};${fr.result}`)
};
fr.addEventListener('error', (err) => {
window.webkit.messageHandlers.jsError.postMessage(`FileReader threw, error: ${err}`)
})
fr.readAsDataURL(data);
} catch (err) {
// TODO: better log the error, currently only TypeError: Type error
window.webkit.messageHandlers.jsError.postMessage(`JSError while downloading document, url: ${url}, err: ${err}`)
}
})();
// null is needed here as this eval returns the last statement and we can't return a promise
null;
""") { (result, err) in
if (err != nil) {
debugPrint("JS ERR: \(String(describing: err))")
}
}
}
}
答案 2 :(得分：0)
自从 macOS 11.3 和 iOS 14.5 以来，我们终于有了处理下载的 API。
但在撰写本文时（2021 年 6 月），文档仍然非常有限：WKDownloadDelegate
将 WKNavigationDelegate 添加到您的 WKWebView.navigationDelegate
在您的 WKNavigationDelegate 工具上：
func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, preferences: WKWebpagePreferences, decisionHandler: @escaping (WKNavigationActionPolicy, WKWebpagePreferences) -> Void) {
if navigationAction.shouldPerformDownload {
decisionHandler(.download, preferences)
} else {
decisionHandler(.allow, preferences)
}
}
点击任何链接时都会调用此方法。
当 WKWebView 检测到该链接用于下载文件时，navigationAction.shouldPerformDownload 将为真。
也在您的 WKNavigationDelegate 工具上：
func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void) {
if navigationResponse.canShowMIMEType {
decisionHandler(.allow)
} else {
decisionHandler(.download)
}
}
如果您在第一种方法中回答 decisionHandler(.allow, preferences)，这将被调用，这意味着 WKWebView 没有将该链接识别为下载，并将尝试显示它。
navigationResponse.canShowMIMEType 将为 false。
创建一个 WKDownloadDelegate
在您的 WKWebView 工具中：
func webView(_ webView: WKWebView, navigationAction: WKNavigationAction, didBecome download: WKDownload) {
download.delegate = // your `WKDownloadDelegate`
}
func webView(_ webView: WKWebView, navigationResponse: WKNavigationResponse, didBecome download: WKDownload) {
download.delegate = // your `WKDownloadDelegate`
}
当您对 .download 部分中描述的任何方法回答 1. 时，将调用其中一个方法。如果是第一种方法，则调用第一个，如果是第二种方法，则调用第二个。
您需要为每个下载分配一个委托，但可以为所有下载指定一个委托。
在您的 WKDownloadDelegate 工具中：
func download(_ download: WKDownload, decideDestinationUsing response: URLResponse, suggestedFilename: String, completionHandler: @escaping (URL?) -> Void) {
let url = // the URL where you want to save the file, optionally appending `suggestedFileName`
completionHandler(url)
}
这将在 WKWebView 准备开始下载时调用，但需要目标 URL。
可选地，也在您的 WKDownloadDelegate 工具中：
func downloadDidFinish(_ download: WKDownload) {
}
这将在下载完成时调用。
WKDownloadDelegate 上还有一些有助于处理错误的方法，请查看文档以了解更多详细信息（上面提供的链接）。macOS 11.3 和 iOS 14.5 上受支持。