Move a view when scrolling in UITableView

Question

I have a UIView with a UITableView below it:

What I would like to do is to have the view above the UITableView move up (out of the way) when the user starts scrolling in the table in order to have more space for the UITableView (and come down when you scroll down again).

I know that this is normally done with a table header view, but my problem is that my table view is inside a tab (actually it is a side-scrolling page view implemented using TTSliddingPageviewcontroller). So while I only have one top UIView there are three UITableViews.

Is it possible to accomplish this manually? My first thought is to put everything in a UIScrollView, but according to Apple's documentation one should never place a UITableView inside a UIScrollView as this leads to unpredictable behavior.

Answer 1

Swift 3 & 4:

    var oldContentOffset = CGPoint.zero
    let topConstraintRange = (CGFloat(0)..<CGFloat(140))

    func scrollViewDidScroll(_ scrollView: UIScrollView) {

        let delta =  scrollView.contentOffset.y - oldContentOffset.y

        //we compress the top view
        if delta > 0 && yourConstraint.constant > topConstraintRange.lowerBound && scrollView.contentOffset.y > 0 {
            yourConstraint.constant -= delta
            scrollView.contentOffset.y -= delta
        }

        //we expand the top view
        if delta < 0 && yourConstraint.constant < topConstraintRange.upperBound && scrollView.contentOffset.y < 0{
            yourConstraint.constant -= delta
            scrollView.contentOffset.y -= delta
        }
        oldContentOffset = scrollView.contentOffset
    }

Answer 2

Since UITableView is a subclass of UIScrollView, your table view's delegate can receive UIScrollViewDelegate methods.

In your table view's delegate:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    static CGFloat previousOffset;
    CGRect rect = self.view.frame;
    rect.origin.y += previousOffset - scrollView.contentOffset.y;
    previousOffset = scrollView.contentOffset.y;
    self.view.frame = rect;
}