ios - UICollectionView 自定义布局页脚 View 不粘在 Collection View 的底部

Question

我正在关注this guide为了制作类似 Pinterest 的 Collection View 布局，它工作得很好，直到我想向它添加页脚 View 。

在 prepare() 方法中，我添加了以下代码:

// Add Attributes for section footer
let footerAtrributes = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter, with: IndexPath(item: 0, section: 0))
footerAtrributes.frame = CGRect(x: 0, y: collectionView.bounds.maxY, width: UIScreen.main.bounds.width, height: myFooterHeight)
cache.append(footerAtrributes)

调用collectionView:viewForSupplementaryElementOfKind:atIndexPath:后，我可以将页脚添加到collectionView，但它不在正确的y位置。

像这样:

自从我调用collectionView.reloadData()以来，如果进一步滚动它就会崩溃。我收到的错误是:

layout attributes for supplementary item at index path changed without invalidating the layout.

我认为 y 位置不正确，但我真的不知道该放什么。

随着 UICollectionView 更新(加载更多项目)，如何将其设置到正确的位置？

Answer 1

此错误:

layout attributes for supplementary item at index path changed without invalidating the layout.

是为FooterView设置布局的原因

所以你必须为 View 进行布局

这是我的CollectionView的示例

let historyCollection: UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 10, right: 0)
        layout.minimumInteritemSpacing = 0
        layout.minimumLineSpacing = 20
        layout.scrollDirection = .vertical

        let historyCollection = UICollectionView(frame: CGRect.zero, collectionViewLayout: layout)
        historyCollection.register(CodiHistoryCell.self, forCellWithReuseIdentifier: "history")
        historyCollection.register(fooderSection.self, forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: "footer")
        historyCollection.isScrollEnabled = true
        historyCollection.backgroundColor = UIColor.clear
        historyCollection.translatesAutoresizingMaskIntoConstraints = false
        return historyCollection
    }()

所以在你命名你的标识符之后

UICollectionElementKindSectionFooter, withReuseIdentifier: "footer"

你必须将它放在我在 Controller 类中所做的“FooterView”中

import UIKit

class fooderSection: UICollectionReusableView {

        let checkBtn: UIButton = {
            let checkBtn  = UIButton(type: .custom)
            checkBtn.setImage(UIImage(named: "loadMoreIcon"), for: .normal)
            checkBtn.contentMode = UIView.ContentMode.scaleAspectFit
            checkBtn.translatesAutoresizingMaskIntoConstraints = false
            return checkBtn
        }()



    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

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

            self.addSubview(checkBtn)

            //this is how it's going to show in the bottonVIEW
just play while this values
            NSLayoutConstraint.activate([
                checkBtn.centerXAnchor.constraint(equalTo: self.centerXAnchor),
                checkBtn.centerYAnchor.constraint(equalTo: self.centerYAnchor),
                checkBtn.widthAnchor.constraint(equalToConstant: 70),
                checkBtn.heightAnchor.constraint(equalToConstant: 70)
                ])

        }
    }

您还必须为 FooterView 设置引用尺寸

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        return CGSize(width: view.frame.width, height: interface.frame.height * 0.1)
    }