Disappearing UICollectionViewCells on landscape or

问题:

I have a problem managing my UICollectionsView with flowlayout and orientation. Basically, the problems happens when I switch to landscape, some of the UICollectionViewCells are missing. They reappear once I start scrolling. It should be able to show all the cell since there is so much more room on the contentSize.

I even tried in my layout:

- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    return YES;
}

With the same results.

Anyone have any ideas on this problem? I included a image on how my layout is organized and the expected behavior:

To add more details, each of the color coded cells belongs to its own section and I am shifting my 2nd section to the right on orientation change using:

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
    NSArray* attributesToReturn = [super layoutAttributesForElementsInRect:rect];

    for (UICollectionViewLayoutAttributes* attributes in attributesToReturn) {
        NSIndexPath* indexPath = attributes.indexPath;
        if (nil == attributes.representedElementKind) {
            attributes.frame = [self layoutAttributesForItemAtIndexPath:indexPath].frame;
        } else {
            NSString *kind = attributes.representedElementKind;
            attributes.frame = [self layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:indexPath].frame;
        }
    }
    return attributesToReturn;
}

It seems the number of items in the layoutAttributesForElementsInRect are completely different in landscape and in portrait.

回答1:

Finally figure it out. I increased my the rect to a large size when it's on landscape on:

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
    CGRect *newRect = CGRectMake(0,0, screensize.width, screensize.height);
    NSArray* attributesToReturn = [super layoutAttributesForElementsInRect:newRect];
    ...
    }