WKWebView not rendering correctly in iOS 10

Question

I have WKWebView inside the UITableViewCell. The web view load request and then after finished loading, I'll resize the web view height to be equal to its content height, then adjust table view cell height to fit accordingly.

What happened was the web view only displays the area that fit the screen size. When I scroll down, everything is white. But I see that the web view rendered with correct height, tap and hold on the white area on the web view still see selection. Zooming with pinch makes the web view area that displaying on the screen visible, but other areas sometimes become white.

It works fine on iOS 8 and 9. I have created a sample project to demonstrate this behaviour here: https://github.com/pawin/strange-wkwebview

Open Radar: https://openradar.appspot.com/radar?id=4944718286815232

Update: This issue is resolved in iOS11

Answer 1

You need to force the WKWebView to layout while your UITableView scrolls.

// in the UITableViewDelegate
func scrollViewDidScroll(scrollView: UIScrollView) {
    if let tableView = scrollView as? UITableView {
        for cell in tableView.visibleCells {
            guard let cell = cell as? MyCustomCellClass else { continue }
            cell.webView?.setNeedsLayout()
        }
    }
}