UICollectionView poor scrolling performance with simple UICollectionViewCell

Question

I'm using UICollectionView to show grid based View in iPad. I have only 200 (20rows x 10 columns) cells at a time on screen, each cell contain one UILabel only. It starts to get slower on scrolling and not smooth like in TableView.

I don't know the reason for this slower scrolling performance. How do I improve?

Thanks in advance!

I have 3 collectionviews, but the main content uicollectionview is the one which has been tagged 2. Here is my code

if (collectionView.tag==0) { //This tagged collection view is for Left side selection box

    LeftSelectionBoxItem *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"SelectionCell" forIndexPath:indexPath];

    return cell;
}
else if (collectionView.tag==1){ //This tagged collection view is for to show column names

    TopColumnItem *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ColumnCell" forIndexPath:indexPath];
    cell.columnName.text = [NSString stringWithFormat:@"%@",[self.columnNames objectAtIndex:indexPath.item]];

    return cell;
}
else if (collectionView.tag==2) { //This tagged collection view is for to show main content

    GridItem *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"GridCell" forIndexPath:indexPath];
    cell.dataLabel.text = [NSString stringWithFormat:@"%@",[[self.dataModel objectAtIndex:indexPath.section] objectForKey:[self.columnNames objectAtIndex:indexPath.item]]];

    return cell;
}
else {
    return nil;
}

If possible, please post what you have in "- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath" — Paramasivan Samuttiram
– Paramasivan Samuttiram, Commented Dec 3, 2012 at 12:41

lehn0058 · Accepted Answer · 2012-12-14 12:36:11Z

3

Having a lot of UILabels is sometimes expensive. Try changing them to CATextLayers instead, as these have much less overhead. Note that if you do this and use rasterizing, you will need to tell the layer to rasterize for retina display devices too.

answered Dec 14, 2012 at 12:36

lehn0058

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7 Comments

lehn0058 Over a year ago

I created a simple mockup of the layout you described, with only 30 cells and 2 CALayers in each. I had three different cell types (mainly just changing where the CALayers were located) and I notice the performance issues you mentioned. When I had only 1 CATextLayer in each cell and only had one type of cell, I did not notice any performance issues. I wonder if having multiple types of cells cause this?

Jirune Over a year ago

thanks first, and I ll try your suggestions and let you know.

lehn0058 Over a year ago

Also, if your cells have rounded corners or shadows, they will also have significant performance issues. UICollectionViews and UITableViews both have this issue because they need to re-render objects as they re-enter the screen (the whole dequeueReusableCellWithReuseIdentifier thing).

lehn0058 Over a year ago

Not sure if you are still looking into this, but another thing I have noticed is having logic that moves items around inside of cells in between uses can cause huge performance problems. For instance, I created a UICollectionView with one reuse identifier. Each cell only had text, but I had it located in different locations in the cell at different sizes (to the left, right, top, bottom). Instead of doing this, creating 4 different cells with their own specific layout and their own reuse identifiers significantly improved performance.

Jirune Over a year ago

Sorry I didn't try CATextLayer yet, because I have some other priorities than improving the performance right now. But sure I ll try our your idea before an app is getting ready to launch. And regarding separate reuse identifiers, I have done the same like you.:-) thanks again!

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