How to rearrange collection view cell when device orientation changes

Question

Collection view looks fine when in portrait mode. But when it landscape mode the cells do not rearrange .. they remain in the same place.

I have added autolayout so that the collection view stretches to fill the screen and the collection view has a constant height constraint.

My view hierarchy is like this

View ->ScrollView->ContentView |--> Problematic collection view (one above notifications label) | |-> Tableview (one after after the notifications label) | |->Collection view (black space on top)

The code for the collection view is

-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;}
-(NSInteger)collectionView:(UICollectionView *)collectionView
numberOfItemsInSection:(NSInteger)section
{
 return 14;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
             cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if (collectionView==self.offerCollectionView) {
    sliderCollectionInHomeScreen *myCell = [collectionView dequeueReusableCellWithReuseIdentifier:@"reuseIdForSlider"
                                                                                     forIndexPath:indexPath];
    myCell.labelForShopName.text = [[self.arrayForOfferSlider objectAtIndex:indexPath.row] objectForKey:@"shop_name"];
    myCell.labelForOfferName.text = [[self.arrayForOfferSlider objectAtIndex:indexPath.row] objectForKey:@"offer_title"];
    myCell.offerImage.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[[self.arrayForOfferSlider objectAtIndex:indexPath.row] objectForKey:@"img_url"]]]];

    ;


    return myCell;
}

Answer 1

I don't know if this is correct . But this has worked for me for the time being

-(void) didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrient{

//[self.categoryCollectionView reloadData];
UICollectionViewFlowLayout * lay =[[UICollectionViewFlowLayout alloc] init];
if (UIDeviceOrientationIsLandscape([UIDevice currentDevice].orientation)) {
    [lay setScrollDirection:UICollectionViewScrollDirectionVertical];
}
else{

    [lay setScrollDirection:UICollectionViewScrollDirectionHorizontal];
}


[self.CollectionView setCollectionViewLayout:lay];


}