UICollectionView 에서 orientation이변경할때 landscape, portrait에 따라서 cell 사이즈 자역스럽게 변경하기

1.  orientation이 바뀌었을때 새로운 layout을 변경 적용.

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation duration:(NSTimeInterval)duration

{

...

    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];

    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;

    layout.minimumInteritemSpacing = 0.f;

    layout.minimumLineSpacing = 0.f;

    layout.sectionInset = UIEdgeInsetsZero;

    [self.collectionView setCollectionViewLayout:layout animated:YES];

    [_collectionView scrollToItemAtIndexPath:currentIndexPath             atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];

}

2. UICollectionView delegate 에서 함수 사이즈 return

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

{

    if (UIInterfaceOrientationIsPortrait([[UIApplication sharedApplication] statusBarOrientation])) {

        return CGSizeMake(320.f, 180.f);

    }

    return CGSizeMake(568.f, 320.f);

}