Swift-UICollectionView基本使用

import UIKit

class CollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    
    var collectionView : UICollectionView! = nil
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        
        return 28
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellID", for: indexPath)
        cell.backgroundColor = UIColor.yellow
        
        return cell
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        self.navigationItem.title = "collectionView"
        
        setupUI()
    }
    
    private func setupUI() {
        
        let layout = UICollectionViewFlowLayout()
        layout.itemSize = CGSize(width: kSCREEN_W / 4, height: kSCREEN_W / 4)
        
        self.collectionView = UICollectionView(frame:self.view.bounds, collectionViewLayout: layout)
        collectionView.backgroundColor = UIColor.white
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "cellID")
        self.view .addSubview(collectionView)
    }

    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destination.
        // Pass the selected object to the new view controller.
    }
    */

}