"removeFromSuperview" NEVER work on UIApplication? - ios

Question

How to remove subviews?
I am trying to integrate GIF by creating UIView and UIImageView programmatically.
It works fine to show GIF but when the function of hiding if is called, there is no response.
Here are the codes of both functions.
class CustomLoader: UIView {
static let instance = CustomLoader()
var viewColor: UIColor = .black
var setAlpha: CGFloat = 0.5
var gifName: String = ""
lazy var transparentView: UIView = {
let transparentView = UIView(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height))
transparentView.backgroundColor = viewColor.withAlphaComponent(setAlpha)
transparentView.isUserInteractionEnabled = false
return transparentView
}()
lazy var gifImage: UIImageView = {
var gifImage = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 60))
gifImage.contentMode = .scaleAspectFit
gifImage.center = transparentView.center
gifImage.isUserInteractionEnabled = false
gifImage.loadGif(name: gifName)
return gifImage
}()
func showLoaderView() {
self.addSubview(self.transparentView)
self.transparentView.addSubview(self.gifImage)
self.transparentView.bringSubview(toFront: self.gifImage)
UIApplication.shared.keyWindow?.addSubview(transparentView)
}
func hideLoaderView() {
self.transparentView.removeFromSuperview()
}
}

Answer 1

A couple of thoughts:
I’d suggest you add a breakpoint or a logging statement in hideLoaderView and make sure you’re getting to that line.
You should make the init method to this class private to make sure you’re not calling hideLoaderView on some separate instance. When dealing with singletons, you want to make sure you can’t accidentally create another instance.
But I tested your code, and it works fine. Your problem probably rests with where and how you call this (and making init private, you might find where you might be using it inappropriately).
In the comments below, you said:
I simply call the function "CustomLoader().hideLoaderView()" Both are being called technically. What do you mean by "where I using it inappropriately?"
That is the root of the problem.
The CustomLoader() of CustomLoader().hideLoaderView() will create a new instance of CustomLoader with its own transparencyView, etc., which is precisely what the problem is. You’re not hiding the old view that was presented earlier, but trying to hide another one that you just created and was never displayed.
If you instead use that static, e.g. CustomLoader.instance.showLoaderView() and CustomLoader.instance.hideLoaderView(), then the problem will go away. Then you will be hiding the same view that your previously showed.
By the way, a few other unrelated observations:
If this is a singleton or shared instance, the convention would be to call that static property shared, not instance.
By the way, you aren’t using this CustomLoader as a UIView, so I’d not make it a UIView subclass. Don’t make it a subclass of anything.
You would obviously eliminate that self.addSubview(transparentView) line, too.
The bringSubview(toFront:) call is unnecessary.
You should avoid referencing UIScreen.main.bounds. You don’t know if your app might be in multitasking mode (maybe this isn’t an issue right now, but it’s the sort of unnecessary assumption that will cause problems at some later date). Just refer to the bounds of the UIWindow to which you’re adding this. You should also update this frame when you show this view, not when you create it (in case you changed orientation in the intervening time, or whatever).
By the way, using keyWindow is discouraged in iOS 13 and later, so you might eventually want to remove that, too.
When adding the gifImage (which I’d suggest renaming to gifImageView because it’s an image view, not an image), you should not reference the center of its superview. That’s the coordinate of the transparent view in its super view’s coordinate system, which could be completely different than the transparent view’s own coordinate system. In this case, it just happens to work, but it suggests a fundamental misunderstanding of view coordinate systems. Reference the bounds of the transparentView, not its center.
If you’re going to expose viewColor and setAlpha, you should pull the setting of the transparentView’s color out of the lazy initializer and into showLoaderView, at the very least. Right now, if you show the loader once, and then change the color, and try to show it again, you won’t see the new color.
The same issue applies with the gif image. So, I’d move that to the didSet observer.
Thus, pulling this all together:
class CustomLoader{
static let shared = CustomLoader()
private init() { }
var dimmingColor: UIColor = .black
var dimmingAlpha: CGFloat = 0.5
var gifName: String = "" { didSet { gifImage.loadGif(name: gifName) } }
lazy var transparentView: UIView = {
let transparentView = UIView()
transparentView.isUserInteractionEnabled = false
return transparentView
}()
lazy var gifImageView: UIImageView = {
var gifImage = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 60))
gifImage.contentMode = .scaleAspectFit
gifImage.isUserInteractionEnabled = false
return gifImage
}()
func showLoaderView() {
guard let window = UIApplication.shared.keyWindow else { return }
transparentView.frame = window.bounds
transparentView.backgroundColor = dimmingColor.withAlphaComponent(dimmingAlpha)
gifImageView.center = CGPoint(x: transparentView.bounds.midX, y: transparentView.bounds.midY)
transparentView.addSubview(gifImageView)
window.addSubview(transparentView)
}
func hideLoaderView() {
transparentView.removeFromSuperview()
}
}

Answer 2

Why you are using transparentView while you are have a CustomLoader instance view
Try to use this
class CustomLoader: UIView {
static let instance = CustomLoader()
var viewColor: UIColor = .black
var setAlpha: CGFloat = 0.5
var gifName: String = ""
init() {
super.init(frame: UIScreen.main.bounds)
backgroundColor = viewColor.withAlphaComponent(setAlpha)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
lazy var gifImage: UIImageView = {
var gifImage = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 60))
gifImage.backgroundColor = .red
gifImage.contentMode = .scaleAspectFit
gifImage.center = center
gifImage.isUserInteractionEnabled = false
gifImage.loadGif(name: gifName)
return gifImage
}()
func showLoaderView() {
addSubview(self.gifImage)
UIApplication.shared.keyWindow?.addSubview(self)
}
func hideLoaderView() {
removeFromSuperview()
}
}