如何确定当前在滚动视图中显示哪个子视图？

Question

我是一个快速的初学者。我有以下视图设置，如下面的屏幕截图所示。

它由顶部的CollectionView和两个单元格（已完成并打开）和一个UISCrollsview组成，其下方有两个TableView子视图。

我希望能够滚动到下一个视图（打开Tableview列表）并通过更改顶部的选定单元格（OPEN）来指示。反之亦然，如果我点击OPEN，我希望下面的ScrollView自动滚动到正确的子视图。

所以我的问题是：

1. 如何确定正在滚动显示的当前子视图？
2. 如何根据顶部集合视图中选定的单元格滚动到正确的子视图？



以下是控制器类的代码：

class OrdersViewController: UIViewController {

@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var ordersListSV: UIScrollView!

var orderStatus: [String] = ["Completed", "Open"]

override func viewDidLoad() {
    super.viewDidLoad()

    self.navigationItem.title = "ORDERS"

    //creating the first view to show
    let completedOrderView: CompletedOrdersTableViewController = CompletedOrdersTableViewController(nibName: "CompletedOrdersTableViewController", bundle: nil)
    //showing the first view
    self.addChildViewController(completedOrderView)
    self.ordersListSV.addSubview(completedOrderView.view)
    completedOrderView.didMove(toParentViewController: self)

    //creating the second view to show
    let openOrderView: OpenOrdersTableViewController = OpenOrdersTableViewController(nibName: "OpenOrdersTableViewController", bundle: nil)
    //showing the second view
    self.addChildViewController(openOrderView)
    self.ordersListSV.addSubview(openOrderView.view)
    openOrderView.didMove(toParentViewController: self)

    //Adding the second view to the frame
    var OpenOrderViewFrame: CGRect = openOrderView.view.frame
    OpenOrderViewFrame.origin.x = self.view.frame.width
    openOrderView.view.frame = OpenOrderViewFrame

    //Allowing it to scroll over to the second view
    self.ordersListSV.contentSize = CGSize(width: ordersListSV.bounds.width * 2, height: ordersListSV.bounds.height)

}

}

扩展OrdersViewController：UICollectionViewDelegate，UICollectionViewDataSource {

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return orderStatus.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "OrderStatusCollectionViewCell", for: indexPath) as! OrderStatusCollectionViewCell

    cell.lbOrderState.text = orderStatus[indexPath.row].uppercased()

    return cell

}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    print(indexPath.item)


}

override func viewDidAppear(_ animated: Bool) {

    super.viewDidDisappear(false)

    let indexPathForFirstRow = NSIndexPath.init(row: 0, section: 0)

    collectionView?.selectItem(at: indexPathForFirstRow as IndexPath, animated: false, scrollPosition: .top)

}

}