How to remove blank space inside WKScrollView after change WKWebview frame height? - ios

Question

How to remove the blank area after change WKWebview's frame height?
I want change webview's height when keyboard show up, but after the frame height changed, there are an extra space below the HTML body. And the height of this extra blank area is about the height of keyboard.
Here is the code snippet:
NotificationCenter.default.rx
.notification(UIApplication.keyboardDidShowNotification)
.subscribe(onNext: { [weak self] keyboardConfig in
if let userInfo = keyboardConfig.userInfo{
let keyboardBounds = (userInfo["UIKeyboardFrameEndUserInfoKey"] as! NSValue).cgRectValue;
self?.webView.snp.remakeConstraints({ make in
make.left.right.top.equalToSuperview();
/// remake from screen height to below height.
make.height.equalTo(UIScreen.main.bounds.size.height - keyboardBounds.size.height);
});
}
});

Answer 1

Finally I still don't know how to remove this extra blank area, but I have figure out a workaround.
Since WKScrollView is a subclass of UIScrollView, so the UIScrollView Delegate also works for WKScrollView;
Therefore the contentOffset can be force reseted in the UIScrollView scrollViewDidScroll delegate method. Code snippet is provided below.
/// Change webview frame when keyboard appear.
NotificationCenter.default.rx
.notification(UIApplication.keyboardDidShowNotification)
.subscribe(onNext: { [weak self] keyboardConfig in
if let userInfo = keyboardConfig.userInfo, let this = self {
let keyboardBounds = (userInfo["UIKeyboardFrameEndUserInfoKey"] as! NSValue).cgRectValue;
this.webView.snp.remakeConstraints({ make in
make.left.right.top.equalToSuperview();
/// remake from screen height to below height.
make.height.equalTo(UIScreen.main.bounds.size.height - keyboardBounds.size.height);
});
let originalOffset = this.webView.scrollView.contentOffset;
DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
this.webView.scrollView.contentOffset = originalOffset;
}
}
});
/// Force reset contentOffset when the contentOffset is out of HTML Body
extension YourWebviewVC: UIScrollViewDelegate{
internal func scrollViewDidScroll(_ scrollView: UIScrollView) {
self.adjustWebviewOffsetFor(scrollView);
}
private func adjustWebviewOffsetFor(_ scrollView: UIScrollView, animated: Bool = false){
let currentY = scrollView.contentOffset.y + scrollView.frame.height;
if currentY > scrollView.contentSize.height{
let maxOffset = scrollView.contentSize.height - scrollView.frame.height;
scrollView.setContentOffset(CGPoint(x: 0, y: maxOffset), animated: animated);
}
}
}
/// Don't forgot set webview scroolView's delegate, for example
self.webView.scrollView.delegate = self;
self.webView.scrollView.showsVerticalScrollIndicator = false;