UICollectionView - Drag Cells outside the UICollectionView to specific UIViews - ios

Question

I have a UICollectionView with alot of UICollectionViewCells inside it.
Searched alot, but couldn't find anything near this issue.
My goal is to drag one of the Pink squares (UICollectionViewCell) to the Gray view (UIView).
You can think of it like dragging a folder on your desktop to your trash can except that I dont want the Pink square to be deleted. Or dragging a icon from your dock (it snaps back).
When the pink area hits the gray area it should just go back to its original position and the same when dropping out anywhere else using some kind of easy statement.
Can anyone help me out or redirect me to some references or samples?
Much appreciated, if you would like more info. Let me know.

Answer 1

If i managed to understand you correctly, i did something very similar once before, i found its much better to use a fake image of the cell, instead of the cell itself.
So for example, cell number 2 is starting to be dragged, you immediately call "SetHidden=YES", and draw at the exact same place a fake one with a simple draw method:
UIGraphicsBeginImageContext(self.cell.bounds.size);
[self.cell.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This one you can move as you like, and when it should go back, you do it the same way.
Hope this helps you..

Answer 2

this worked for me in swift 3:
class DragAndDropGestureManager: NSObject {
var originalPosition: CGPoint?
var draggedView: UIView?
var viewSize: CGSize?
var originalZIndex: CGFloat = 0
#objc func handleDrag(_ recognizer: UIPanGestureRecognizer) {
switch recognizer.state {
case .began:
if let view = recognizer.view {
draggedView = view
originalPosition = view.frame.origin
viewSize = view.frame.size
originalZIndex = view.layer.zPosition
view.layer.zPosition = 1
}
case .changed:
if let view = recognizer.view {
let currentPosition = recognizer.location(in: view.superview!)
let newPosition = CGPoint(x: currentPosition.x - (viewSize!.width / 2.0), y: currentPosition.y - (viewSize!.height / 2.0))
view.frame.origin = newPosition
} else {
self.finishDrag()
}
case .ended:
finishDrag()
default:
print("drag default \(recognizer.state.rawValue)")
}
}
func finishDrag() {
self.draggedView?.frame.origin = originalPosition!
self.draggedView?.layer.zPosition = originalZIndex
originalZIndex = 0
originalPosition = nil
draggedView = nil
}
}
i added a gesture recognizer in the function public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
like this:
if self.dragManager != nil && cell.gestureRecognizers == nil {
cell.addGestureRecognizer(UIPanGestureRecognizer(target: dragManager!, action: #selector(DragAndDropGestureManager.handleDrag)))
}
the if, is for not adding gesutre recognition more than once because the cell are being reused
don't forget to add collectioView.clipToBounds = false otherwise the dragged cell will be clipped when trying to move out of the collection view's bounds