Scroll to anchor in webView

Question

We would like to open a WebView with a specific location opened in the view. Therefore we would like to scroll to an anchor OR jump to it before it is shown.

We tried to execute a javascript inside of the viewWillAppear , but it does not work. If we execute it in the viewDidAppear we have a jump to the anchor which is not a valid solution.

WebContentView (Simple Storyboard with a UIView containing a single WebView):

class WebContentViewController: UIViewController, UIWebViewDelegate {
    @IBOutlet weak var webView: UIWebView!

    var fileName: String?
    var screenName: String?

    override func viewDidLoad() {
        super.viewDidLoad()
        webView.backgroundColor = UIColor.white

        let url = URLRequest(url: Bundle.main.url(forResource: fileName, withExtension: "html")!)
        webView.loadRequest(url);
        webView.delegate = self
    }

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

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        guard let screenName = screenName else {
            return
        }

        webView.stringByEvaluatingJavaScript(from: "window.location.href = '#2-einsatz-von-google-analytics';")
    }

    override func viewDidAppear(_ animated: Bool) {
        //webView.stringByEvaluatingJavaScript(from: "window.location.href = '#2-einsatz-von-google-analytics';") //creates a jump instead of a scrole
    }
}

Tried solutions and known questions:

• Using scrollTo(hash) {location.hash = "#" + hash;}; scrollTo("anchor"); scrollTo(hash) {location.hash = "#" + hash;}; scrollTo("anchor"); How to scroll HTML page to given anchor using jQuery or Javascript?
• Is it possible to send a hash tag to a file url in UIWebView?

How can we accomplish a "smooth" scroll to the anchor or a jump before it is visible?

Answer 1

If you are familiar with UIScrollView , you should know that you can use setContentOffset method. By default, the UIWebView has a scrollView property:

var scrollView: UIScrollView The scroll view associated with the web view.

So, what you can do -for example- is:

webView.scrollView.setContentOffset(CGPoint(x: 0, y: 100), animated: true)

Also , I think you should use it after the webView finished loading, you can achieve this by implementing UIWebViewDelegate - webViewDidFinishLoad :

func webViewDidFinishLoad(_ webView: UIWebView) {
    webView.scrollView.setContentOffset(CGPoint(x: 0, y: 100), animated: true)
}

Hope this helped.