ios - 如何在 Swift 中正确设计 UICollectionViewCell

Question

我在没有使用 Storyboard的情况下创建了 UICollection View 。我将在下面分享我的代码和屏幕截图。我想帮助了解如何使用约束和 anchor 正确排列 UICollection View Cell。感谢您帮助我解决我的问题。

这是我在 collectionview.swift 中的代码；

class ProductViewController : UICollectionViewController, UICollectionViewDelegateFlowLayout {


var product : Product?
var productdetail : [ProductDetail]?
var categories : [NSDictionary] = [NSDictionary]()
var mainurl  = "http://www.example.com"
var idforurl = ""


override func viewDidLoad() {
    idforurl = (product?.id)!
    mainurl = ("\(mainurl)\(idforurl)")
    print(mainurl)
    //self.mainurl += (product?.id)!

    fetchproductDetail()

    collectionView?.backgroundColor = .white
    navigationItem.title = self.product?.name
    self.navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Close", style: .plain, target: self, action: #selector (handleCloseBook))

    collectionView?.register(ProductDetailCell.self, forCellWithReuseIdentifier: "cellId")
    let layout =  collectionView?.collectionViewLayout as? UICollectionViewFlowLayout
    //layout?.scrollDirection = .vertical
    layout?.minimumLineSpacing = 40
    collectionView?.isPagingEnabled = false





}

func handleCloseBook() {

    dismiss(animated: true, completion: nil)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    return CGSize(width: view.frame.width / 4, height: view.frame.height / 5)

}

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


    let selectedproduct = self.productdetail?[indexPath.row]
    let productVC = DetailViewController()
    productVC.detailproduct = selectedproduct
    let navController = UINavigationController(rootViewController: productVC)
    present(navController, animated: true, completion: nil)



}


override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let pagecell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! ProductDetailCell

    let products1 = productdetail?[indexPath.item]
    pagecell.product = products1
    return pagecell

}

override func numberOfSections(in collectionView: UICollectionView) -> Int {

    return 1

}

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return productdetail?.count ?? 0
}

func fetchproductDetail () {

    if let url = URL(string: mainurl) {
        URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in

            if let err = error {

                print("fetch error",err)

            }

            guard let data = data else{return}

            do {
                self.productdetail = []

                let json = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as! [String:AnyObject]

                if let tempData = json["data"] as? [NSDictionary] {
                    for category in tempData {
                        if let tempResult = category["Menu"] as? NSDictionary {
                            self.categories.append(tempResult)
                        }
                    }
                }

                for category in self.categories {

                    let product =  ProductDetail(dictionary: category as! [String : Any])
                    self.productdetail?.append(product)
                    print(product.productname)
                    print(product.productdesc)

                }

                DispatchQueue.main.async {
                    self.collectionView?.reloadData()
                }

            }

            catch let JsonErr {

                print("Failed to Parse json properly", JsonErr)
            }


        }).resume()
    }

}





}

这是 Collection View 单元文件；

class ProductDetailCell : UICollectionViewCell {
        var product : ProductDetail? {
            didSet{
                textLbl.text =  product?.productname
                priceLbl.text = product?.productprice

                guard let productImages = product?.productimage else {return}
                let baseUrl = "http://www.example.com"
                guard let url = URL(string: baseUrl) else {return}
                productImage.image = nil

                URLSession.shared.dataTask(with: url) { (data, response, error) in

                    if let err = error {

                        print("Error has been occurred", err)

                    }

                    guard let imagedata = data else{return}
                    let image = UIImage(data: imagedata)

                    DispatchQueue.main.async {

                        self.productImage.image = image
                    }

                    }.resume()

            }
            }

    let textLbl: UILabel = {

        let label = UILabel()
        label.text = "Veri Yok!"
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont(name: "Avenir-Light", size: 12)
        label.textAlignment = .center
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 1
        label.minimumScaleFactor = 0.1
        label.adjustsFontSizeToFitWidth = true

        return label
    }()

    let priceLbl: UILabel = {

        let label = UILabel()
        label.text = "Veri Yok!"
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont(name: "Avenir-Light", size: 12)
        label.textAlignment = .center
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 1
        label.adjustsFontSizeToFitWidth = true

        return label
    }()

    let productImage : UIImageView = {

        let imageView = UIImageView()
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.contentMode = .scaleAspectFit
        imageView.clipsToBounds = false
        imageView.image = #imageLiteral(resourceName: "amazon_icon")
        return imageView

    }()


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

        addSubview(productImage)
        productImage.topAnchor.constraint(equalTo: topAnchor, constant: 5).isActive = true
        productImage.leftAnchor.constraint(equalTo: self.leftAnchor, constant: 5).isActive = true
        productImage.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -10).isActive = true
        productImage.rightAnchor.constraint(equalTo: self.rightAnchor, constant: -5).isActive = true
        productImage.widthAnchor.constraint(equalToConstant: frame.size.width / 5).isActive = true



        addSubview(textLbl)
        textLbl.topAnchor.constraint(equalTo: productImage.bottomAnchor, constant: 2).isActive = true
       // textLbl.leftAnchor.constraint(equalTo: self.leftAnchor, constant: -5).isActive = true
        //textLbl.rightAnchor.constraint(equalTo: self.rightAnchor, constant: 5).isActive = true
       // textLbl.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
        textLbl.heightAnchor.constraint(equalToConstant: 30).isActive = true
        textLbl.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true


        addSubview(priceLbl)
        priceLbl.topAnchor.constraint(equalTo: textLbl.bottomAnchor, constant: 2).isActive = true
        // textLbl.leftAnchor.constraint(equalTo: self.leftAnchor, constant: -5).isActive = true
        //textLbl.rightAnchor.constraint(equalTo: self.rightAnchor, constant: 5).isActive = true
        //textLbl.heightAnchor.constraint(equalToConstant: 40).isActive = true
        priceLbl.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true

    }

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


     }

}

最后我在模拟器上得到了下面的结果

正如您所看到的，我的 Collection View 单元格未正确设置，我希望它们处于完美的正方形，并且单元格中间的空间也应该减少。再次感谢您的帮助。

Answer 1

既然您已经使用了 Storyboard，那么您要做的第一件事就是对单元格使用 1:1 的比例约束。这将确保单元格始终是完美的正方形。

其次，为了减少单元格之间的填充，你可以在 View 加载时做这样的事情:

let columns:CGFloat = 3
let sW = self.view.frame.width
let padding = sW / 32      // 32 points being the padding space between cells
cellWidth = (sW - (padding*(columns+1))) / columns