I'm developing an app where users swipe through "cards" which are basically UIViews populated with data from an API.
When the app first opens, cards are created and added as subviews to the superview. Every time a user swipes, the card is removed from the superview.
While the user is swiping, more cards are created and cached in the background.
When the user is on the last card, I add the cached cards to the superview, behind the card that is currently being displayed.
The issue is that while the cards are being added to the superview, my gesture recognizer stops working/glitches (user can't swipe). After a few seconds it starts working again and the user can swipe.
How do I stop the recognizer from glitching? Any insight would be appreciated.
Thank you!
Here's the code that creates/adds the cards // Creating the cards func createCards(firstCall:Bool){
APICall.begin () { (info) in
DispatchQueue.main.async {
for i in info {
let frontView = frontView()
let backView = backView()
// Set up front and back views
self.viewSetup(view: frontView)
self.viewSetup(view: backView)
// Set up card view
let view = cardView(frame: frame)
view.addSubview(backView)
view.addSubview(frontView)
self.viewSetup(view: view)
view.isHidden = true
// function that add recognizer
self.dragging(view: view)
// cacheCard
if !firstCall{
self.cache.add(cardView: view)
// add to view
}else{
self.view.addSubview(view)
}
}
// Reveal current card
if firstCall {
self.view.subviews.last?.isHidden = false
}
print("DONE")
}
}
}
Heres the code that add the recognizers/ adds cache
// dragging gesture helper
func draggig(card: view){
let gesture = UIPanGestureRecognizer(target: self, action: #selector(ViewController.wasDragged(_:)))
view.addGestureRecognizer(gesture)
view.isUserInteractionEnabled = true
}
// dragged gestrues
func wasDragged(_ gesture: UIPanGestureRecognizer){
// Only allow dragging when front is showing
if(showingFront){
// Dragging code
let helper = draggingBeganHelper(gesture: gesture)
let card:UIView = helper[0] as! UIView
var rotation:CGAffineTransform = helper[1] as! CGAffineTransform
var stretch:CGAffineTransform = helper.last as! CGAffineTransform
if gesture.state == UIGestureRecognizerState.ended {
rotation = CGAffineTransform(rotationAngle: 0)
stretch = rotation.scaledBy(x: 1, y: 1)
//Remove card from superview
card.removeFromSuperview()
// Store cards in cache
if(self.view.subviews.count == lastCardIndex + cardOffset){
createCards(false)
}
// When at the second to last card
else if self.view.subviews.count == lastCardIndex+1{
if cardCacheArray.isEmpty {
createCards(true)
}
else{
DispatchQueue.main.async {
for i in cardCacheArray{
self.view.insertSubview(i, belowSubview: self.view.subviews[lastCardIndex])
}
self.cache.empty()
}
}
}
}
}
}
func draggingBeganHelper(gesture: UIPanGestureRecognizer) -> [AnyObject]{
// Card dragging gesture setup
let translation = gesture.translation(in: self.view)
let card = gesture.view
card?.center = CGPoint(x: (card?.center.x)! + translation.x, y: (card?.center.y)! + translation.y)
let xFromCenter = (card?.center.x)! - self.view.bounds.width/2
let scale = min(100/abs(xFromCenter),1)
let rotation = CGAffineTransform(rotationAngle: xFromCenter/200)
let stretch = rotation.scaledBy(x: scale, y: scale)
card?.transform = stretch
return [card!,rotation as AnyObject,stretch as AnyObject]
}
