Adding a loading indicator to your infinite UICollectionView

The easiest way for adding a loading indicator to your asynchronous data view in under 5 minutes without any third-party code

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The Problem

When working with Restful APIs, we typically want to divide the fetched data into multiple pages and not load all data at once. As a result, we have to gradually load the data as soon as the user reached the bottom of the previously fetched data. From a UX perspective, we have to inform the user that we’re loading more results when he gets the end of UICollectionView. There are many Cocoapod libraries to show an UIActivityIndicatorView at the bottom of an UICollectionView. Still, I believe that the issue is too small and simple to fix by installing third-party libraries. Let’s tackle this without installing any Cocoapods.

The Solution

The trick here is to add a loading cell into our UICollectionView, containing the UIActivityIndicatorView (or any custom animation item) and display it as the last UICollectionViewCell. This means the cell becomes visible when the user reaches the end of the available data.

The Implementation

First, we create a custom loading cell:

Second, we change the UICollectionView delegation code as follows:

That is all! You have successfully created your own custom loading cell without using any third-party code!

Code Explanation

There are three adaptions we need to make this work.

1. When returning the number of items in numberOfItemsInSection, we want to return one more than the data count (line 3). This cell overflowing will be our loading cell.
2. Next, in cellForItemAt we need to check whether we have reached the end of the data. If so, we return the IndicatorCell; otherwise we return the normal cell, in this case PostCell (lines 8 and 16 following).
3. The last adaption is the cell height returned from sizeForItemAt. This is only required to reduce the height of the IndicatorCell (line 29).

Thanks for reading!

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