How to check if a cell has been displayed Swift

Question

When I display my tableview I've made my cells come with an animation like this.

 func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {

             cell.alpha = 0
             let rotation = CATransform3DTranslate(CATransform3DIdentity, -250, 20, 0)
             cell.layer.transform = rotation
             UIView.animateWithDuration(0.9){
             cell.alpha = 1
             cell.layer.transform = CATransform3DIdentity

    }

It's working like this but when i go down and then up again to see the previous cells the animation still exists.

Show I believe I have to check if the cell has been displayed.

Something I try is to use didEndDisplayingCell function and put the cell.tag inside an array and then I was checking if the current cell is inside that array with array.contains(cell.tag) but it didn't work. Actually the animation worked only for the three first cells and then nothing.

see this once http://stackoverflow.com/questions/3326658/determine-if-a-tableview-cell-is-visible — Anbu.Karthik, Jul 21 '16 at 09:57
@Anbu.Karthik thanks for your answer but I want to know which cells have been seen so the animation will not be used again to cells that have been seen — mike vorisis, Jul 21 '16 at 10:03
Add the cell indexPath to your array instead of tag, the cells are being reused, so the tag will be the same for the reused cells. — James P, Jul 21 '16 at 10:03

score 5 · Accepted Answer · answered Jul 21 '16 at 10:06

You should keep an array of indexPaths, adding to it whenever a cell is displayed. This way you can check if the cell has already animated.

if (!indexPaths.contains(indexPath)) {
    indexPaths.append(indexPath)
    cell.alpha = 0
    let rotation = CATransform3DTranslate(CATransform3DIdentity, -250, 20, 0)
    cell.layer.transform = rotation
    UIView.animateWithDuration(0.9){
        cell.alpha = 1
        cell.layer.transform = CATransform3DIdentity
    }
}

Thank you.. It worked! I will accept your answer in 3 minutes — mike vorisis, Jul 21 '16 at 10:08

score 1 · Answer 2 · answered Jul 21 '16 at 10:07

As @James-P mentioned in comments - just create an array

var indexPathArray = [NSIndexPath]()

and rewrite your willDisplayCell method:

func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {

    if !indexPathArray.contains(indexPath) {

        indexPathArray.append(indexPath)

        cell.alpha = 0
        let rotation = CATransform3DTranslate(CATransform3DIdentity, -250, 20, 0)
        cell.layer.transform = rotation
        UIView.animateWithDuration(0.9){
            cell.alpha = 1
            cell.layer.transform = CATransform3DIdentity
        }
    }
}

score 1 · Answer 3 · answered Jul 21 '16 at 10:08

1

what you can do is put the indexpath of cell in an array and check if the indexpath is in array.if the indexpath is in array dont perform animation

answered Jul 21 '16 at 10:08

harpreetSingh

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How to check if a cell has been displayed Swift

3 Answers3