UICollectionView not consistent layout, UICollectionViewFlowLayout

Question

I am having trouble displaying the cells in a UICollectionView in a consistent manner. The initial display of the cells is correct, however every time the user scrolls past and then back to a group of cells the display is incorrect. Rows should only ever contain 2 or 1 cell(s). 2 cells each taking half the display width, 1 cell taking full width.

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return [self preferredSizeForIndexPath:indexPath];
}

- (CGSize)preferredSizeForIndexPath:(NSIndexPath *)indexPath {

    BOOL isLastObjectInSection = NO;
    NSString *sectionKey = [[arrCollectionData[indexPath.section] allKeys] objectAtIndex:0];
    DLog(@"SectionKey: %@", sectionKey);
    NSArray *arrSection = [arrCollectionData[indexPath.section] objectForKey:sectionKey];
    DLog(@"ArrSection: %@", arrSection);

    if ( arrSection[indexPath.row] == arrSection.lastObject ) {
        if( arrSection.count % 2 != 0 ) {
            isLastObjectInSection = YES;
        }
    }

    CGSize cellSize = CGSizeZero;
    if (UIDeviceOrientationIsLandscape([[UIDevice currentDevice] orientation])) {
        if (isLastObjectInSection == YES) {
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_LANDSCAPE_WIDE, IPAD_BADGE_HEIGHT_LANDSCAPE_WIDE);
        } else {
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_LANDSCAPE, IPAD_BADGE_HEIGHT_LANDSCAPE);
        }
    } else {
        if (isLastObjectInSection == YES) {
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_WIDE, IPAD_BADGE_HEIGHT_WIDE);
        } else {
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH, IPAD_BADGE_HEIGHT);
        }
    }
    DLog(@"CellSize: %@", NSStringFromCGSize(cellSize));
    return cellSize;

}

Below is a sample of the collection data.

Printing description of self->arrCollectionData:
<__NSArrayI 0x94bbc40>(
{
    "March 12, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b2430>",
        "<FMLeafTimelineContainer: 0x94b3670>"
    );
},
{
    "February 25, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b4500>"
    );
},
{
    "February 14, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b48f0>",
        "<FMLeafTimelineContainer: 0x94b3a60>"
    );
},
{
    "February 12, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b3ce0>",
        "<FMLeafTimelineContainer: 0x94b2b00>"
    );
},
{
    "February 4, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b4e90>",
        "<FMCommunityTimelineContainer: 0x94b5050>",
        "<FMCommunityTimelineContainer: 0x94b5f70>"
    );
},
{
    "January 30, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6ad0>",
        "<FMCommunityTimelineContainer: 0x94b5a90>"
    );
},
{
    "January 24, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b5d00>",
        "<FMCommunityTimelineContainer: 0x94b6d90>"
    );
},
{
    "January 22, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6440>"
    );
},
{
    "January 21, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6260>",
        "<FMCommunityTimelineContainer: 0x94b62e0>",
        "<FMCommunityTimelineContainer: 0x94b70c0>",
        "<FMCommunityTimelineContainer: 0x94b55a0>",
        "<FMCommunityTimelineContainer: 0x94b82d0>",
        "<FMCommunityTimelineContainer: 0x94b78b0>"
    );
},
{
    "December 20, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b53f0>"
    );
},
{
    "December 6, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b7200>"
    );
},
{
    "December 4, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b72b0>"
    );
},
{
    "November 19, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b7ae0>"
    );
}
)

The pics below all demonstrate the same section of the collection view.

Answer 1

Problem was caused by a subview of the parent having a fixed frame size assigned at instantiation. Overrode setFrame: for UICollectionView subclass to assign values of subview frames and every time a cell is dequeued and requeued call setFrame: to adjust accordingly.