我已经有一个 UICollectionView ，它垂直滚动并显示一组具有固定大小的自定义 UICollectionViewCell 。

现在我被要求在所有其他单元格顶部显示另一个 UICollectionView，它应该 水平滚动 并且其 单元格大小是动态 (我只会在异步网络调用完成后知道大小)。此外，这个内部集合 View 可能并不总是需要显示 (这取决于从网络调用接收到的数据)，但如果是，它应该只显示一次(在所有内容之上)。

我的问题是:处理第二个内部集合 View 的最佳方法应该是什么？我应该将它添加到外部 View Controller 作为它的不同类型的单元格，还是作为节标题？
也许另一种布局方法会更好？

编辑: 更多注意事项:

最佳答案

"how the best way to deal with this second and inner collection view should be?"

"Should I add it to the outer view controller as a different kind of cell of it, or maybe as a section header?"

"I'd need to animate the inner collection view when I'm going to show it"

"The whole thing should be vertically scrollable, this inner collection view should not stick to the top of the screen."

import UIKit

class ViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    // Programmically add our empty / custom ParentCollectionView
    let parentCollectionView: ParentCollectionView = {
        let layout = UICollectionViewFlowLayout()
        let cv = ParentCollectionView(frame: .zero, collectionViewLayout: layout)
        cv.translatesAutoresizingMaskIntoConstraints = false
        return cv
    }()


    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        setup()

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func setup() {
        // Assign this viewcontroller's collection view to our own custom one.
        self.collectionView = parentCollectionView

        // Set delegate and register Static and empty cells for later use.
        parentCollectionView.delegate = self
        parentCollectionView.register(StaticCollectionViewCell.self, forCellWithReuseIdentifier: StaticCollectionViewCell.identifier)
        parentCollectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: UICollectionViewCell.identifier)

        // Add simple Contraints
        let guide = self.view.safeAreaLayoutGuide

        parentCollectionView.topAnchor.constraint(equalTo: guide.topAnchor).isActive = true
        parentCollectionView.leftAnchor.constraint(equalTo: guide.leftAnchor).isActive = true
        parentCollectionView.rightAnchor.constraint(equalTo: guide.rightAnchor).isActive = true
        parentCollectionView.bottomAnchor.constraint(equalTo: guide.bottomAnchor).isActive = true
    }

    // MARK: - CollectionView

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        // Erroneous Data from your network call, data should be a class property.
        let data = Array.init(repeating: "0", count: 12)

        // Skip if we dont have any data to show for the first row.
        if (indexPath.row == 0 && data.count > 0) {

            // Create a new empty cell for reuse, this cell will only be used for the frist cell.
            let cell = parentCollectionView.dequeueReusableCell(withReuseIdentifier: UICollectionViewCell.identifier, for: IndexPath(row: 0, section: 0))

            // Programmically Create a Horizontal Collection View add to the Cell
            let horizontalView:HorizontalCollectionView = {
                // Only Flow Layout has scroll direction
                let layout = UICollectionViewFlowLayout()
                layout.scrollDirection = .horizontal
                // Init with Data.
                let hr = HorizontalCollectionView(frame: cell.frame, collectionViewLayout: layout, data: data)
                return hr
            }()
            // Adjust cell's frame and add it as a subview.
            cell.addSubview(horizontalView)
            return cell
        }

        // In all other cases, just create a regular cell.
        let cell = parentCollectionView.dequeueReusableCell(withReuseIdentifier: StaticCollectionViewCell.identifier, for: indexPath)
        // Update Cell.

        return cell
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // 30 sounds like enough.
        return 30
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        //If you need your first row to be bigger return a larger size.
        if (indexPath.row == 0) {
            return StaticCollectionViewCell.size()
        }


        return StaticCollectionViewCell.size()
    }

}

import UIKit

class ParentCollectionView: UICollectionView {

    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
        super.init(frame: frame, collectionViewLayout: layout)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

import Foundation
import UIKit

class HorizontalCollectionView: UICollectionView, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    // Your Data Model Objects
    var data:[Any]?

    // Required
    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
        super.init(frame: frame, collectionViewLayout: layout)
    }

    convenience init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout, data:[Any]) {
        self.init(frame: frame, collectionViewLayout: layout)

        // Set These
        self.delegate = self
        self.dataSource = self
        self.data = data
        // Setup Subviews.
        setup()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // return zero if we have no data to show.
        guard let count = self.data?.count else {
            return 0
        }
        return count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = self.dequeueReusableCell(withReuseIdentifier: DynamicCollectionViewCell.identifier, for: indexPath)
        // Do Some fancy Animation when scrolling.
        let endingFrame = cell.frame
        let transitionalTranslation = self.panGestureRecognizer.translation(in: self.superview)
        if (transitionalTranslation.x > 0)  {
            cell.frame = CGRect(x: endingFrame.origin.x - 200, y: endingFrame.origin.y - 100, width: 0, height: 0)
        } else {
            cell.frame = CGRect(x: endingFrame.origin.x + 200, y: endingFrame.origin.y - 100, width: 0, height: 0)
        }

        UIView.animate(withDuration: 1.2) {
            cell.frame = endingFrame
        }

        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        // See DynamicCollectionViewCell size method, generate a random size.
        return DynamicCollectionViewCell.size()
    }

    func setup(){
        self.backgroundColor = UIColor.white
        self.register(DynamicCollectionViewCell.self, forCellWithReuseIdentifier: DynamicCollectionViewCell.identifier)
        // Must call reload, Data is not loaded unless explicitly told to.
        // Must run on Main thread this class is still initalizing.
        DispatchQueue.main.async {
            self.reloadData()
        }
    }

}

import Foundation
import UIKit

class DynamicCollectionViewCell: UICollectionViewCell {

    /// Get the Size of the Cell
    /// Will generate a random width element no less than 100 and no greater than 350
    /// - Returns: CGFloat
    class func size() -> CGSize {
        let width = 100 + Double(arc4random_uniform(250))
        return CGSize(width: width, height: 100.0)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setup() {
        self.backgroundColor = UIColor.green
    }
}

import Foundation
import UIKit

class StaticCollectionViewCell: UICollectionViewCell {

    /// Get the Size of the Cell
    /// - Returns: CGFloat
    class func size() -> CGSize {
        return CGSize(width: UIScreen.main.bounds.width, height: 150.0)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setup() {
        self.backgroundColor = UIColor.red
    }


}

import UIKit

extension UICollectionViewCell {

    /// Get the string identifier for this class.
    ///
    /// - Returns: String
    class var identifier: String {
        return NSStringFromClass(self).components(separatedBy: ".").last!
    }

}

关于ios - 另一个 Collection View 中的 Collection View : section header or cell?，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51906411/