CODEWITHSUNDEEP
iosobjective-cuicollectionviewuicollectionviewcellcagradientlayer
Shayan Jalil
Shayan Jalil

Reputation: 588

UICollectionViewCell strange behaviour. Cells not updating layer correctly

I have a UICollectionView with multiple cells on which I add a CAGradient layer representing the color of each cell. The problem is that when I push another view controller on top of the present view controller and then pop the second view controller, my collection view cells shift colors in a random order. To give you an idea I have attached screenshots.

This is the original order of the cells. This is correct This is the original order of the cells. This is correct

This happens when I push another view controller and then return This happens when I push another view controller and then return You can see that the cells shifted their colors even though I changed nothing.

This is the code I use to initialize the cells.

[collectionview reloadData] is called in -viewWillAppear so the cells load every time the view appears

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    [self filterRecords];
    MyCell *cell = (MyCell*)[collectionView dequeueReusableCellWithReuseIdentifier:@"ProspectCVCell" forIndexPath:indexPath];


    for (int i = 0; i < [eventsSortedForAddedDate count]; i++)
    {
        Events* event = (Events*)[eventsSortedForAddedDate objectAtIndex:i];

        if ([event.activityLevel.activityName isEqualToString:@"None"])
            continue;

        color = [[event activityLevel] color];

        if (![color isEqualToString:@"#FFCCCCCC"])
            break;
        else
            color = nil;
    }


    if (!([color length] > 0) || color == nil)
    {
        color = @"#FFCCCCCC";
    }

    UIColor* myColor = [self getUIColorObjectFromHexString:color alpha:.9];

    //cell.backgroundColor = myColor;

    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = cell.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[myColor CGColor], (id)[[UIColor whiteColor] CGColor], nil];
    gradient.locations = [NSArray arrayWithObjects:[NSNumber numberWithFloat:0.0f], [NSNumber numberWithFloat:0.85f],  nil];
    //[cell.layer insertSublayer:gradient atIndex:0];
    [cell.layer insertSublayer:gradient atIndex:0];


    cell.prospectImageView.layer.shadowColor = [UIColor blackColor].CGColor;
    cell.prospectImageView.layer.shadowOffset = CGSizeMake(0, 3.0);
    cell.prospectImageView.layer.shadowRadius = 3.0;
    cell.prospectImageView.layer.shadowOpacity = 0.8;

    cell.cellLabel.text = p.displayName;

    cell.layer.borderWidth = 0.5f;
    cell.layer.borderColor = [UIColor whiteColor].CGColor;

    return cell;
}

There is nothing wrong in the way I get the color, I have debugged multiple times and checked that the colors I get are the correct ones. If I do

cell.backgroundColor = myColor;

The cells do not change their colors and function as expected. So I am pretty sure that the problem lies with the CAGradientLayer.

I have tried everything that I could think of but nothing seems to work!

Upvotes: 1

Views: 1067

Answers (1)

Ketan Parmar
Ketan Parmar

Reputation: 27438

Try this once,

 [cell.layer insertSublayer:gradient atIndex:[[cell.layer sublayers] indexOfObject:[[cell.layer sublayers] lastObject]]];

instead of

 [cell.layer insertSublayer:gradient atIndex:0];

Update :

As asked in comment, Apple doc states about dequeueReusableCellWithReuseIdentifier,

Call this method from your data source object when asked to provide a new cell for the collection view. This method dequeues an existing cell if one is available or creates a new one based on the class or nib file you previously registered.

And second thing you can also remove previous layers and then can add new one at index 0. it is better because it not increase number of layer which is not necessary.

Upvotes: 1

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