BLACK FRIDAY: Save 50% on my Swift books and videos! >>

How to control the user interface of a WKWebView using WKUIDelegate

Paul Hudson       @twostraws

By default WKWebView works sort of like Safari, albeit in a single view rather than having tabs. If you want something more advanced – being able to monitor opening and closing windows, override behavior for JavaScript user interface, and so on – then the WKUIDelegate protocol is for you.

First, make your view controller conform to it by adding WKUIDelegate to its list of protocols. Second, assign your view controller to the uiDelegate property of your web view:

yourWebView.uiDelegate = self

Finally, implement whichever of the optional methods of WKUIDelegate takes your interest. For example, you can make WKWebView show a custom alert controller when any web page uses the alert() JavaScript function:

func webView(_ webView: WKWebView, runJavaScriptAlertPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping () -> Void) {
    let ac = UIAlertController(title: "Hey, listen!", message: message, preferredStyle: .alert)
    ac.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
    present(ac, animated: true)
    completionHandler()
}

There’s also runJavaScriptConfirmPanelWithMessage for showing confirm and deny UI, runJavaScriptTextInputPanelWithPrompt for requesting user text input, and so on.

Note: You must call the completion handler. JavaScript’s alerts are blocking, which means JavaScript execution will not continue until the alert finishes. As a result, WebKit will complain if you don’t let it know when you’re done.

Available from iOS 10.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Help support Hacking with Swift

This site is funded by Hacking with Swift supporters who buy my e-books. If you can, please support my work – it comes packed with bonus material!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Click here to visit the Hacking with Swift store >>