Removing views from a UIStackView with removeArrangedSubview()
Removing views from a UIStackView with removeArrangedSubview() 관련
That was a long chapter, and I hope you learned a lot. But you deserve a break, so I have some good news: it's trivial to remove views from a UIStackView. Heck, at its simplest it's just a matter of telling removeArrangedSubview() which view you don’t want then removing that view from its superview – the others are automatically resized and re-arranged to fill the space.
However, using removeArrangedSubview() doesn’t remove the view altogether – it keeps the view in memory, which is helpful if you plan to re-add it later on because you can avoid recreating it. Here, though, we actually want to remove the web view and destroy it entirely, and that can be done with a call to removeFromSuperview() instead.
In this particular project, we need to do a little more:
- We want the delete button to work only if there's a web view selected.
- We want to find the location of the active web view inside the stack view, then remove it.
- If there are now no more web views, we want to call
setDefaultTitle()to reset the user interface. - We need to find whatever web view immediately follows the one that was removed.
- We then make that the new selected web view, highlighting it in blue.
We already pointed the delete button at a method called deleteWebView(), so all you need to do is plug this in. I've added comments to make sure it's all clear:
@objc func deleteWebView() {
// safely unwrap our webview
if let webView = activeWebView {
if let index = stackView.arrangedSubviews.firstIndex(of: webView) {
// We found the webview – remove it from the stack view and destroy it
webView.removeFromSuperview()
if stackView.arrangedSubviews.count == 0 {
// go back to our default UI
setDefaultTitle()
} else {
// convert the Index value into an integer
var currentIndex = Int(index)
// if that was the last web view in the stack, go back one
if currentIndex == stackView.arrangedSubviews.count {
currentIndex = stackView.arrangedSubviews.count - 1
}
// find the web view at the new index and select it
if let newSelectedWebView = stackView.arrangedSubviews[currentIndex] as? WKWebView {
selectWebView(newSelectedWebView)
}
}
}
}
}
So, although the act of removing a view from a UIStackView is just a matter of calling either removeArrangedSubview() or removeFromSuperview() depending on whether you want to use it again, we need to do a little more to make sure the user interface updates correctly.
The last thing we're going to do is talk about multitasking on iPad, and add a few user interface clean ups to make the project complete…
