Swift滑动视图

Question

I'm new to Swift and iOS development, and am looking to set up a series of views, or "cards", that can be swiped left and right, with the next/previous cards remaining at the edges to indicate that they are there. This is done in iOS App Store previews:

So far all I've really found is this Medium article: iOS Swift: Swipe View . However I'm not sure if this is the right way to do what I'm asking above, and I also don't know how to get the next/previous cards to remain at the edges on each swipe.

Does anyone have any tips for achieving this?

Answer 1

The easiest way will be to use UICollectionView and UICollectionViewFlowLayout . UICollectionViewFlowLayout is provided out of the box and is very powerful.

Basically you need:

1. Add UICollectionView to your view controller.
2. By default UICollectionView goes with Flow layout selected.
3. Configure UICollectionViewFlowLayout
   • Set scroll direction to Horizontal
   • Define item size and spacing. Keep in mind that you need just one item to be fully visible; in addition spaces to the left and right should be visible as well; further more you need to show pieces of previous and next cards, so some basic math waiting for you:). One small trick to make you very first and very last cards be centered properly: you should specify vertical section insets to be equal to the sum of visible width of previous card plus space between cards.

Steps above should be enough to have vertically scrollable cards view. But it will not look great! To make it great you probably need perfectly to center most appropriate card after user end scrolling. To achieve sticky scrolling you need to work with the following UICollectionViewDelegate methods:

// compute collection view content offset in method bellow
override func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    ...
}

// compute targetContentOffset in method bellow 
override func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    ...
}

... last hint: to make collection view deceleration look quick in code of your view controller do:

self.collectionView?.decelerationRate = UIScrollViewDecelerationRateFast

Paging indicator:

In example that you provide there is a paging control that reflects current item and overall items count. You need to add UIPageControll manually; you can do it in storyboard. The best place to update page control state will be:

// method in UICollectionView delegate that you need to define.
// update your paging info in method bellow.
override func scrollViewDidScroll(scrollView: UIScrollView) {
    ...    
}

Remarks:

Methods that deal with scroll view that i've listed are inherited by UICollectionViewDelegate from UIScrollViewDelegate . UICollectionView itself derived from UIScrollViewDelegate .