Refreshing or reloading data on just single object inside a collectionViewCell

Question

i'm trying to update just one single object inside my costumViewCell, i've tried collectionView.reloadItems(at: [IndexPath]), but this method updates my entire cell, which results to a very jittering animations.

here is a sample code of my collectionView cell,

class MyCollectionViewCell: UICollectionViewCell {


    @IBOutlet weak var buttonA: UIButton!
    @IBOutlet weak var buttonB: UIButton!


    var myButtonTitle: String? {
        didSet{
            if let title = myButtonTitle {
                self.buttonA.setTitle(title, for: .normal)
            }
        }
    }

    var buttonActionCallBack: (()->()?)

    override func awakeFromNib() {
        super.awakeFromNib()
        self.animation()

        buttonA.addTarget(self, action: #selector(buttonACallBack), for: .touchUpInside)
    }


    @objc fileprivate func buttonACallBack() {
        self.buttonActionCallBack?()
    }


    fileprivate func animation() {
        UIView.animate(withDuration: 1.0) {
            self.buttonA.transform = CGAffineTransform(translationX: 20, y: 20)
            self.buttonB.transform = CGAffineTransform(translationX: 20, y: 20)
        }
    }
}

here is my DataSource method.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! MyCollectionViewCell

    let item = mainList[indexPath.row]

    collectionView.reloadItems(at: <#T##[IndexPath]#>)
    cell.buttonActionCallBack = {
        () in
        //Do Stuff and Update Just ButtonA Title
    }
    return cell
}

cheers.

From what I understand, you are trying to change the title of the button inside the cell when the button is tapped. This should not be done from the data source object itself. Instead this is the responsibility of the cell itself. So basically you write the code needed to change the title of the button in the button's action method. — nayem, Jan 25 '19 at 10:35

score 0 · Accepted Answer · answered Jan 25 '19 at 11:16

The jittering animation occurs because of this collectionView.reloadItems(at: [IndexPath]) line written inside cellForItemAt which is really wrong approach because cellForItemAt called many a times leads to infinite loop of reloading IndexPath's. Instead of that, you just reload only that part which is necessary when action occurs.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! MyCollectionViewCell
        let item = mainList[indexPath.row]
        //collectionView.reloadItems(at: <#T##[IndexPath]#>) #removed
        cell.buttonActionCallBack = {
            () in
            //Do Stuff and Update Just ButtonA Title
            collectionView.reloadItems(at: [indexPath]) //Update after the change occurs to see the new UI updates
        }
        return cell
    }

Refreshing or reloading data on just single object inside a collectionViewCell

1 Answers1