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如何在推送wkwebview的viewcontroller之前预加载wkwebview?

preload wkwebview loading swift ios

cmii · 技术社区 · 5 年前

我问这个问题是因为经过一些研究,我在网上没有找到令人满意的答案。

我的需要很简单,我有一个uiTableViewController,当我单击一个单元格时,我需要显示一个加载程序(在加载wkWebViewContent时),然后推下一个uiViewController,其中wkWebView已经加载。

我试过这个:

class TableViewController: UITableViewController, WKNavigationDelegate {

   var webviewToLoad:WKWebView!

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        let htmlString = "some html content"


        webviewToLoad = WKWebView(frame: .zero, configuration: WKWebViewConfiguration())
        webviewToLoad.navigationDelegate = self
        webviewToLoad.loadHTMLString(htmlString, baseURL: Bundle.main.resourceURL)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "postview"{
            let destinationController = segue.destination as! ViewController
            destinationController.webView= webviewToLoad
        }
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        print("Loaded!")
        self.performSegue(withIdentifier: "postview", sender: self)
    }

}

class ViewController: UIViewController, WKUIDelegate {

    var webView: WKWebView!

    override func loadView() {

        let webConfiguration = WKWebViewConfiguration()
        webView = WKWebView(frame: .zero, configuration: webConfiguration)
        webView.uiDelegate = self
        self.view = webView
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }
}

didFinish 调用,但最终的WkWebView为空。

也许这不是正确的方法,有什么想法吗?

2 回复 | 直到 5 年前

matt 5 年前

调用了DidFinish,但最终的WkWebView为空

因为你从未做过任何事不空白。你的代码说:

var webviewToLoad:WKWebView!
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    webviewToLoad = WKWebView(frame: .zero, configuration: WKWebViewConfiguration())
    webviewToLoad.navigationDelegate = self
    webviewToLoad.loadHTMLString(htmlString, baseURL: Bundle.main.resourceURL)
}

所以你所做的一切都是关于 webviewToLoad . 但是 网络浏览 是不相同的 webView 出现在Segue之后的视图控制器中:

class ViewController: UIViewController, WKUIDelegate {
    var webView: WKWebView!
}

那是要为其提供内容的Web视图。您根本没有这样做;您的代码都不涉及 WebVIEW 给它内容。

我认为你困惑的核心是:

if segue.identifier == "postview"{
    let destinationController = segue.destination as! ViewController
    destinationController.webView = webviewToLoad
}

你不能简单地用一个Web视图代替另一个,并且期望事情神奇地工作; loadView 仍将导致原始空白Web视图成为您的视图并显示在界面中。

相反,您想要的是这个体系结构:

if segue.identifier == "postview"{
    let destinationController = segue.destination as! ViewController
    // make `loadView` run
    destinationController.loadViewIfNeeded() 
    let webView = destinationController.webView
    // now load _this_ `webView` with content!
    let htmlString = "some html content"
    webView.loadHTMLString(htmlString, baseURL: Bundle.main.resourceURL)
}

cmii 5 年前

因为@matt的回答不完整,所以在推下一个视图控制器之前,我的解决方案是等待WebView加载:

class TableViewController: UITableViewController, WKNavigationDelegate, WKUIDelegate {

    var webviewToLoad:WKWebView!
    var destinationController:ViewController!
    var alert:UIAlertController!

    override func viewDidLoad() {
        super.viewDidLoad()       
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        alert = UIAlertController(title: "Alert", message: "Loading", preferredStyle: .alert)

        destinationController = UIStoryboard.init(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "ViewController") as? ViewController

        destinationController!.loadViewIfNeeded()
        let webView:WKWebView = destinationController!.webView
        webView.navigationDelegate = self
        webView.uiDelegate = self

        self.present(alert, animated: true, completion: nil)

        let htmlString = "my html code"
        webView.loadHTMLString(htmlString, baseURL: Bundle.main.resourceURL)
    }


    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {

        alert.dismiss(animated: false, completion: nil)
        self.navigationController?.pushViewController(destinationController!, animated: true)
    }

}

以及内置WebView的uiviewController:

class ViewController: UIViewController, WKUIDelegate, WKNavigationDelegate {

    var webView: WKWebView!
    @IBOutlet var viewForWebview: UIView!
    @IBOutlet var heightWebviewConstraint: NSLayoutConstraint!

    override func viewDidLoad() {
        super.viewDidLoad()

    }

     override func loadView() {

        super.loadView()

        webView = WKWebView()

        if (webView != nil) {
            webView!.frame = viewForWebview.frame

            webView.translatesAutoresizingMaskIntoConstraints = false

            viewForWebview.addSubview(webView!)

            NSLayoutConstraint.activate([
               webView.topAnchor.constraint(equalTo: viewForWebview.topAnchor),
                webView.bottomAnchor.constraint(equalTo: viewForWebview.bottomAnchor),
                webView.leadingAnchor.constraint(equalTo: viewForWebview.leadingAnchor),
                webView.trailingAnchor.constraint(equalTo: viewForWebview.trailingAnchor)
                ])
        }

    }


    override func viewDidLayoutSubviews() {

        super.viewDidLayoutSubviews()

        heightWebviewConstraint.constant = self.webView.scrollView.contentSize.height
        self.view.setNeedsLayout()
        self.view.setNeedsUpdateConstraints()


    }    
}

此代码在WebView加载期间显示一个uiAlertController,然后关闭警报控制器,并推送下一个已加载WebView的控制器。