ios - uicollectionview layout

UICollectionView diseño no consistente, UICollectionViewFlowLayout

Question

Tengo problemas para visualizar las celdas en un UICollectionView de manera consistente. La visualización inicial de las celdas es correcta, sin embargo, cada vez que el usuario se desplaza hacia atrás y luego hacia atrás a un grupo de celdas, la pantalla es incorrecta. Las filas solo deben contener 2 o 1 celda (s). 2 celdas cada una, ocupando la mitad del ancho de la pantalla, 1 celda ocupando el ancho total.

- (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;

}

A continuación se muestra una muestra de los datos de la colección.

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>"
    );
}
)

Las fotos a continuación muestran la misma sección de la vista de colección.

Answer 1

El problema fue causado por una subvista del padre que tiene un tamaño de fotograma fijo asignado en la instanciación. Overrode setFrame: para que la subclase UICollectionView asigne valores de fotogramas de la subvista y cada vez que una célula es eliminada de la cola y puesta en cola, call setFrame: para ajustar en consecuencia.

Answer 2

Puede intentar calcular dinámicamente el ancho del artículo.

CGFloat fullItemWidth = self.collectionView.bounds.size.width;
NSInteger itemsPerRow = 2;
CGFloat itemWidth = (fullItemWidth - (itemsPerRow-1)*self.collectionView.collectionViewLayout.minimumInteritemSpacing)/itemsPerRow;
if (UIDeviceOrientationIsLandscape([[UIDevice currentDevice] orientation])) {
    if (isLastObjectInSection == YES) {
        cellSize = CGSizeMake(fullItemWidth, IPAD_BADGE_HEIGHT_LANDSCAPE_WIDE);
    } else {
        cellSize = CGSizeMake(halfItemWidth, IPAD_BADGE_HEIGHT_LANDSCAPE);
    }
} else {
    if (isLastObjectInSection == YES) {
        cellSize = CGSizeMake(fullItemWidth, IPAD_BADGE_HEIGHT_WIDE);
    } else {
        cellSize = CGSizeMake(halfItemWidth, IPAD_BADGE_HEIGHT);
    }
}