如何以编程方式创建 UICollectionViewCell [英] How to create UICollectionViewCell programmatically

问题描述

我正在尝试以编程方式创建 UICollectionView.我需要在单元格内添加标签，所以我创建了 CollectionViewCell 类.

I'm trying to create UICollectionView programatically. I need to add labels inside the cells, so I Created CollectionViewCell class.

这是课程:

import UIKit

class MyCollectionViewCell: UICollectionViewCell {

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

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

这是 collectionView 的实现类:

And this is the collectionView implementation class:

import UIKit

class TwoViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {

    let leftAndRightPaddings: CGFloat = 80.0
    let numberOfItemsPerRow: CGFloat = 7.0
    let screenSize: CGRect = UIScreen.main.bounds
    private let cellReuseIdentifier = "collectionCell"
    var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31"]

    override func viewDidLoad() {
        super.viewDidLoad()
        let flowLayout = UICollectionViewFlowLayout()
        let collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: flowLayout)
        collectionView.register(MyCollectionViewCell.self, forCellWithReuseIdentifier: cellReuseIdentifier)

        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.backgroundColor = UIColor.cyan

        self.view.addSubview(collectionView)
    }

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

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
    {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellReuseIdentifier, for: indexPath) as! MyCollectionViewCell
        cell.backgroundColor = UIColor.green
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
    {
        let width = (screenSize.width-leftAndRightPaddings)/numberOfItemsPerRow
        return CGSize(width: width, height: width)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
    {
        return UIEdgeInsets(top: 20, left: 8, bottom: 5, right: 8)
    }        
}

生成单元格时发生错误:

The error happens when the cell produced:

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
{
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(cellReuseIdentifier, forIndexPath: indexPath) as! MyCollectionViewCell

错误是:

Could not cast value of type 'UICollectionViewCell' (0x1033cc820) to 'CollectionViewProgramatically.MyCollectionViewCell' (0x1015a4f88).

推荐答案

你的问题就在这里.在您的 viewDidLoad() 中，您注册了 collectionView 单元格两次.您在第一行将 collectionview 的单元格注册到自定义单元格类，然后在第二行将其注册到 UICollectionViewCell 类.

Your problem lies here. In your viewDidLoad(), you're registering your collectionView cell twice. You are registering the collectionview's cell to your custom cell class in the first line and then in the second line you are registering it to the class UICollectionViewCell.

 collectionView.registerClass(MyCollectionViewCell.self, forCellWithReuseIdentifier: cellReuseIdentifier)
 collectionView.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")

只需删除第二行，您的代码就可以工作了.

Just remove the second line and your code should work.

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