I think I read every answer on this subject and all I had was part of the solution. Most of the time I spent trying to implement KVO method as described by @davew, which occasionally worked, but most of the time left a white space under the content of a WKWebView container. I also implemented @David Beck suggestion and made the container height to be 0 thus avoiding the possibility that the problem occurs if the container height is larger that that of the content. In spite of that I had that occasional blank space.
So, for me, “contentSize” observer had a lot of flaws. I do not have a lot of experience with web technologies so I cannot answer what was the problem with this solution, but i saw that if I only print height in the console but do not do anything with it (eg. resize the constraints), it jumps to some number (e.g. 5000) and than goes to the number before that highest one (e.g. 2500 – which turns out to be the correct one). If I do set the height constraint to the height which I get from “contentSize” it sets itself to the highest number it gets and never gets resized to the correct one – which is, again, mentioned by @David Beck comment.
After lots of experiments I’ve managed to find a solution that works for me:
func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
self.webView.evaluateJavaScript("document.readyState", completionHandler: { (complete, error) in
if complete != nil {
self.webView.evaluateJavaScript("document.body.scrollHeight", completionHandler: { (height, error) in
self.containerHeight.constant = height as! CGFloat
})
}
})
}
Of course, it is important to set the constraints correctly so that scrollView resizes according to the containerHeight constraint.
As it turns out didFinish navigation method never gets called when I wanted, but having set document.readyState step, the next one (document.body.offsetHeight) gets called at the right moment, returning me the right number for height.