CODEWITHSUNDEEP
iosuitableviewuicollectionviewreloaddata
abagmut
abagmut

Reputation: 911

UICollection view reloadData cause recreate visible cell

When I call reloadData method of UICollectionView it cause all visible cell to blink. I found that reason of this is recreation of all visible cells, while UITableView return visible cell in – tableView:cellForRowAtIndexPath: method after reload data.

So, how can I avoid recreation of visible cells in UICollectionView.

Upvotes: 25

Views: 20437

Answers (5)

dungi
dungi

Reputation: 312

Swift Version:

if let indexPaths = collectionView?.indexPathsForVisibleItems {
    collectionView?.reloadItems(at: indexPaths)
}

Upvotes: 4

Oleksandr
Oleksandr

Reputation: 411

You can simply create your own flow layout and set alpha to initial layout attribute, e.g. 

class MyFlowLayout: UICollectionViewFlowLayout {

    override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        let attr = layoutAttributesForItem(at: itemIndexPath)
        attr?.alpha = 1
        return attr
    }
}

It's necessary because by default alpha is 0, and if cells are re-created - you see blinking.

Upvotes: 4

Adam W. Dennis
Adam W. Dennis

Reputation: 476

You need to reload the visible cells, which will not cause the flash seen during reloadData:

[myCollectionView reloadItemsAtIndexPaths:[myCollectionView indexPathsForVisibleItems]];

Upvotes: 19

Bao Lei
Bao Lei

Reputation: 3615

You can try https://github.com/ba01ei/PSTImprovedCollectionView

With this collection view, when you call reloadData, if a cell is still visible, the same cell will be returned from the queue (then you can check the data model attached to the cell and decide whether to re-render)

Upvotes: 1

Wain
Wain

Reputation: 119041

Calling reloadData on either a table or a collection view will recreate (dequeue if possible) all of the (visible) cells and refresh the information about the row / item count and the view content height. So, you will always see a 'blink' because it's animated.

This is by design to inform the user that everything was just updated...

To avoid animation, don't call reloadData. Instead, use visibleCells to get all of the cells that currently exist on the screen and update their contents directly.

Upvotes: 7

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