iphone - UIScrollView custom paging size

Question

paging in UIScrollView is a great feature, what I need here is to set the paging to a smaller distance, for example I want my UIScrollView to page less size that the UIScrollView frame width. Thanks

Answer 1

There is a UIScrollView delegate method you can use. Set your class as the scroll view's delegate, and then implement the following:

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
    CGFloat kMaxIndex = 23;
    CGFloat targetX = scrollView.contentOffset.x + velocity.x * 60.0;
    CGFloat targetIndex = 0.0;
    if (velocity.x > 0) {
        targetIndex = ceil(targetX / (kCellWidth + kCellSpacing));
    } else if (velocity.x == 0) {
        targetIndex = round(targetX / (kCellWidth + kCellSpacing));
    } else if (velocity.x < 0) {
        targetIndex = floor(targetX / (kCellWidth + kCellSpacing));
    }
    if (targetIndex < 0)
        targetIndex = 0;
    if (targetIndex > kMaxIndex)
        targetIndex = kMaxIndex;
    targetContentOffset->x = targetIndex * (kCellWidth + kCellSpacing);
    //scrollView.decelerationRate = UIScrollViewDecelerationRateFast;//uncomment this for faster paging
}

The velocity parameter is necessary to make sure the scrolling feels natural and doesn't end abruptly when a touch ends with your finger still moving. The cell width and cell spacing are the page width and spacing between pages in your view. In this case, I'm using a UICollectionView.