Mac Catalyst - 向 UITableView/UIScrollView 添加单击 + 拖动手势

Question

I am in the process of enabling Catalyst support for a freelancing project — one of the things that I noticed right away is the differing behaviour of scrolling views on MacOS vs iOS. I expected to be able to click and drag UIScrollView s or UITableView s as I would normally in the iOS Simulator, but I am only able to scroll these views using the mouse's scroll wheel (or two finger gesture on a trackpad).

Is there any way I can mimic the UIPanGestureRecognizer behaviour on iOS for a UIScrollView or UITableView using a Click + Drag gesture on MacOS?

Thank you :)

Answer 1

如果Private API是可以接受的，那么 Mac Catalyst 14.0 中的新 API 正是这样做的：

- [UIScrollView _setSupportsPointerDragScrolling:]

Answer 2

I noted the same for UICollectionViews. I decided to use scroll buttons and have them set the selection, and offsets. You can do the same with UIGestureRecognizers in each cell and then set the offsets, etc of the parent UITableView or UICollectionView. I've not thought about simple UIScrollViews.

Answer 3

The following will do the trick:

First a convenience extension:

public extension CGPoint {
    static func - (a: CGPoint, b: CGPoint) -> CGPoint {
        return CGPoint(x: a.x-b.x, y: a.y-b.y)
    }
}

Add a pan gesture to the scroll view:

scrollView.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(onPan(_:))))

And finally the selector:

private var s0: CGPoint = .zero
@objc func onPan(_ gesture: UIPanGestureRecognizer) {
    let ds: CGPoint = gesture.translation(in: scrollView)
    switch gesture.state {
        case .began:
            s0 = scrollView.contentOffset
        case .changed:
            scrollView.contentOffset = CGPoint(x: 0, y: max(0, min(scrollView.contentSize.height-scrollView.height, (s0-ds).y)))
        default: break
    }
}

(Full set of CGPoint convenience methods included here: https://github.com/aepryus/Acheron )

Answer 4

值得注意的是，从 Monterey 开始，如果您在触控板上使用两个手指手势，那么它的工作原理就像在设备上滚动一样——包括弹跳。