How to select item/cell of UICollectionView from code

Question

I have implemented a UICollectionView in my app. My problem is that I need to select (like if the user tapped on it) a cell programmatically. The method:

- (void)selectItemAtIndexPath:(NSIndexPath *)indexPath 
                     animated:(BOOL)animated 
               scrollPosition:(UICollectionViewScrollPosition)scrollPosition

That is part of the UICollectionView class is not what i need to call, since this method does not call:

- (void)collectionView:(UICollectionView *)collectionView 
        didSelectItemAtIndexPath:(NSIndexPath *)indexPath

It just sets the selected property of the cell to YES;

Solution 1

I am calling [self collectionView:yourView didSelectItemAtIndexPath:yourIndexPath] to programmatically select a cell. But in the method cell is always nil. This works perfectly well when user selects a cell.

Solution 2

Yes, this is proper behaviour. Documentation for [selectItemAtIndexPath:animated:scrollPosition:] says:

This method does not cause any selection-related delegate methods to be called.

Solution 3

First, you need to make the target cell visible, otherwise [yourCollectionView cellForItemAtIndexPath:yourIndexPath] always returns nil.

// scroll to the cell
[yourCollectionView scrollToItemAtIndexPath:yourIndexPath
                           atScrollPosition:UICollectionViewScrollPositionBottom 
                                   animated:NO];

// call delegate method
[self collectionView:yourCollectionView didSelectItemAtIndexPath:yourIndexPath];

// now you have selected the cell and can do anything to it in the delegate method :-)