底部集合视图间距问题，我想删除蓝色间距

Question

我得到了单元格之间的空间（用蓝色标记）：

extension ProfileVC: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        if collectionView == self.humanCollectionView {
            let screenWidth = humanCollectionView.bounds.width
            return CGSize(width: screenWidth/3-0, height: screenWidth/3-0)
            
            func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout:
                UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
                return 0
            }
            
            func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout:
                UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
                return 0
            }
            
            func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
                return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
            }
        }

Answer 1

为什么要在collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, sizeForItemAt: IndexPath)委托方法中声明委托函数？

尝试这样做：

import UIKit

class ProfileVC: UICollectionViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        //remember to set the delegates
        self.collectionView.delegate = self
        self.collectionView.dataSource = self
        //this is optional just to test that it is working
        collectionView.backgroundColor = .red
        // Do any additional setup after loading the view.
    }


}

extension ProfileVC: UICollectionViewDelegateFlowLayout {
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        //this is just a test number, here you should return the number of your items
        return 20
    }
    
    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        //you should set reuseIndetifier in storyboard or in code if you create your collectionView programmatically
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "reuseIdentifier", for: indexPath)
        //again this is just a placeholder color to see that it's working
        cell.backgroundColor = .green
        return cell
    }
    func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, sizeForItemAt: IndexPath) -> CGSize {
        let screenWidth = collectionView.bounds.width
        //be sure to use floor or to use a number of items that perfectly fits the width of collectionView
        return CGSize(width: floor(screenWidth/3), height: floor(screenWidth/3))
    }
            
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout:
        UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout:
        UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    }
}

我想补充一点，如果你的 collectionView 的宽度不能被 3 整除，那么单元格之间总会有一些间隙。 您应该自己为每个设备宽度进行数学计算，并为宽度选择适当数量的单元格。 例如对于像 iPhone X 这样具有纵横比的屏幕，我会在纵向使用 3 个单元格，在横向使用 4 个单元格。

你可以这样做：

func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, sizeForItemAt: IndexPath) -> CGSize {
    let screenWidth = collectionView.bounds.width
    let screenHeight = collectionView.bounds.height
    let numberOfCells : CGFloat = screenWidth > screenHeight ? 4 : 3
    return CGSize(width: floor(screenWidth/numberOfCells), height: floor(screenWidth/numberOfCells))
}