Changing y position of view removes tap events - ios

Question

I set a UICollectionView y position outside the screen (set it aligned to the bottom safe area, and offset -154, so it is off screen).
When the app starts, I use a button to move the entire root view up
self.view.center.y -= 154
Both the root view and my UIView appear in expected position, but the UICollectionView can not be tapped. The new zone does not recognize the UIEvent.
I added a gesture to the UICollectionView but it doesn't work. Only the root view zone responds to the UIEvent.
#IBAction func filmRollButton(_ sender: UIButton) {
var toUp = true
if self.toUp == true {
self.view.center.y -= 154
} else {
self.view.center.y += 154
}
self.toUp = !self.toUp
}
// tap - UICollection View appear(y position change)
// tap again - UICollection view disappear
Expected:
Use some method to enable the UICollectionView tap event. (extend root view zone? because only root view zone can be tapped.)
Other simple draw effect like setting the UICollectionView height to 0, then tap button and set the height to 154.

Answer 1

Try using layoutIfNeeded() , to layout subviews right away. Might be pending
#IBAction func filmRollButton(_ sender: UIButton) {
var toUp = true
if self.toUp == true {
self.view.center.y -= 154
self.view.layoutIfNeeded()
} else {
self.view.layoutIfNeeded()
self.view.center.y += 154
}
self.toUp = !self.toUp
}
// tap - UICollection View appear(y position change)
// tap again - UICollection view disappear