NEW: Learn SwiftUI with my free YouTube video series! >>

How to monitor WKWebView page load progress using key-value observing

Swift version: 5.0

Paul Hudson    @twostraws   

iOS often uses a delegate system to report important changes, such as when a table view cell has been tapped or when a web page has finished loading. But the delegate system only goes so far, and if you want fine-grained detailed information sometimes you need to turn to KVO, or "key-value observing."

In the case of seeing how much of a page has loaded in WKWebView, KVO is exactly what you need: each web view has a property called estimatedProgress, and you can be asked to be notified when that value has changed.

First, create a progress view that will be used to show the loading progress:

progressView = UIProgressView(progressViewStyle: .default)
progressView.sizeToFit()

You can place that anywhere you like. Now add the current view controller as an observer of the estimatedProgress property of your WKWebView, like this:

webView.addObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress), options: .new, context: nil)

The .new in that line of code means "when the value changes, tell me the new value."

Finally, implement the observeValue(forKeyPath:) method in your view controller, updating the progress view with the estimated progress from the web view, like this:

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if keyPath == "estimatedProgress" {
        progressView.progress = Float(webView.estimatedProgress)
    }
}

LEARN SWIFTUI FOR FREE I wrote a massive, free SwiftUI tutorial collection, and also have a growing list of free SwiftUI tutorials on YouTube – get started today!

Available from iOS 8.0 – see Hacking with Swift tutorial 4

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.

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!

Average rating: 4.3/5

Click here to visit the Hacking with Swift store >>