Dynamically adding content to UICollectionView - ios

Question

I have a UICollectionView that is backed by a web service. I initially load 100 items from the service into the collection view. When the user reaches the bottom of the view, I dyanmically load the next "page" of content.
This is working, but my collectionView flashes and re-draws the entire view from the top. I am trying to get it to just begin drawing the new content at the bottom of the view.
Code for adding new content to the collectionview:
- (void)insertIntoCollectionView: (int) itemCnt {
// only do the batchupdate for NON-initial load
if(curPage != 0) {
// Add items to main photos array, and update collectionview using batchUpdate
[self.collectionView performBatchUpdates:^{
// Get starting size before update
int resultsSize = itemCnt;
// Create a new array to hold the indexpath for the inserted data
NSMutableArray *arrayWithIndexPaths = [NSMutableArray array];
// Add indexpath objects to the new array to be added to the collection view
for (int i = resultsSize; i < resultsSize + itemCnt; i++) {
[arrayWithIndexPaths addObject:[NSIndexPath indexPathForRow:i inSection:0]];
}
// Update the collectionview
[self.collectionView insertItemsAtIndexPaths:arrayWithIndexPaths];
}
completion:nil];
} else {
[self.collectionView reloadData];
}
curPage++;
Anything obvious? It functionally works, but looks pretty bad with all of the flashing and re-drawing.

Answer 1

OK, managed to fix it myself. I was using the incorrect values for the resultSize variable. The for loop should start at the end of the current array count, and loop through the number of item that we added, thus adding them at the end. I was starting at the beginning of the array index 1 when building the arrayWithIndexPaths, causing it to re-draw the whole view.