Unable to change contentSize of UIScrollview in WKWebView - ios

Question

I'm trying to add a little bit of extra height to the content of a UIScrollView that is within a WKWebView after it loads by adjusting the contentSize property.
I can modify this property, but it somehow keeps changing back to its original size by the time the next layout/display refresh hits.
To test this even further, I attempted to change contentSize in scrollViewDidScroll. Whenever you scroll to the bottom, you can see for a fraction of a second that it's trying add the extra space and keeps reverting back.
I can't reproduce this issue with UIWebView. It works just fine there. Perhaps some changes were added to WKWebView recently? I'm using Xcode 8 and testing on iOS 9/10.

Answer 1

Given my ineptitude with Dropbox I felt badly so put the attached together to try and help you out. If you change the contentInset property of the WKWebView's scrollView rather than contentSize, this seems to work quite well. I agree with you that while you might be able temporarily to change the content size of the scrollView, it reverts quickly; moreover, there are no delegate methods either for UIScrollView or WKWebView that I can find that you might override to counteract this.
The following sample code has a web page and some buttons that allow you to increase or decrease the top and bottom contentInset and animating you to the appropriate point on the scrollView.
import UIKit
import WebKit
class ViewController: UIViewController {
var webView : WKWebView!
var upButton : UIButton!
var downButton : UIButton!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let webFrame = CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: self.view.frame.width - 200, height: self.view.frame.height - 200))
webView = WKWebView(frame: webFrame)
webView.load(URLRequest(url: URL(string: <PUT RELEVANT URL STRING (NB - THAT YOU ARE SURE IS VALID) HERE>)!))
webView.backgroundColor = UIColor.red
webView.scrollView.contentMode = .scaleToFill
self.view.addSubview(webView)
func getButton(_ label: String) -> UIButton {
let b : UIButton = UIButton()
b.setTitle(label, for: .normal)
b.setTitleColor(UIColor.black, for: .normal)
b.layer.borderColor = UIColor.black.cgColor
b.layer.borderWidth = 1.0
return b
}
let upButton = getButton("Up")
let downButton = getButton("Down")
upButton.frame = CGRect(origin: CGPoint(x: 25, y: 25), size: CGSize(width: 50, height: 50))
downButton.frame = CGRect(origin: CGPoint(x: 25, y: 100), size: CGSize(width: 50, height: 50))
upButton.addTarget(self, action: #selector(increaseContentInset), for: .touchUpInside)
downButton.addTarget(self, action: #selector(decreaseContentInset), for: .touchUpInside)
self.view.addSubview(webView)
self.view.addSubview(upButton)
self.view.addSubview(downButton)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func increaseContentInset() -> Void {
guard let _ = webView else { return }
webView.scrollView.contentInset = UIEdgeInsetsMake(webView.scrollView.contentInset.top + 100, 0, webView.scrollView.contentInset.bottom + 100, 0)
webView.scrollView.setContentOffset(CGPoint(x: webView.scrollView.contentInset.left, y: -1 * webView.scrollView.contentInset.top), animated: true)
}
func decreaseContentInset() -> Void {
guard let _ = webView else { return }
webView.scrollView.contentInset = UIEdgeInsetsMake(webView.scrollView.contentInset.top - 100, 0, webView.scrollView.contentInset.bottom - 100, 0)
webView.scrollView.setContentOffset(CGPoint(x: webView.scrollView.contentInset.left, y: -1 * webView.scrollView.contentInset.top), animated: true)
}
}
I hope that helps. If you need an answer based specifically on setting the content size then let me know, but I think this is the best option.