swift - UICollectionView didSelectItemAt() 并根据状态添加/删除 View

Question

我想向选定的单元格添加复选标记。如果随后取消选择该单元格(因此选择了另一个单元格)，我想删除复选标记。顶部 ImageView 独立于 Collection View ，代表用户相机胶卷中选定的单元格。 Collection View 的数据源是从 PHAsset 获取的图像列表。

问题是，如果我不在索引路径处重新加载项目，则取消选择的单元格复选标记不会被删除。另外，如果我滚动浏览 Collection View ，我会看到我什至没有点击的单元格中的随机复选标记。我假设这与细胞的重复使用有关。有人可以帮我吗？

下面是我的 View Controller 和单元格的代码片段...

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: photoCellReuseIdentifier, for: indexPath) as? PhotosCell else { fatalError("Couldn't return a photo cell") }
    let requestOptions = PHImageRequestOptions()
    requestOptions.isSynchronous = true
    requestOptions.isNetworkAccessAllowed = true
    requestOptions.deliveryMode = .highQualityFormat

    photoManager.requestImage(for: photoAssets![indexPath.row], targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFill, options: requestOptions, resultHandler: { (image, nil) in
        cell.photoView.image = image
    })

    if cell.isSelected {
        cell.setupCheckmarkBanner()
    }
    else {
        cell.removeCheckmarkBanner()
    }

    if indexPath.row == 0 && self.isFirstLoad {
        self.selectedImageView.image = cell.photoView.image
        collectionView.selectItem(at: indexPath, animated: false, scrollPosition: UICollectionViewScrollPosition.bottom)
        cell.setupCheckmarkBanner()
        self.isFirstLoad = false
    }


    return cell
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    previousIndexPath = indexPath
    collectionView.reloadItems(at: [indexPath])
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if previousIndexPath != indexPath {
        collectionView.reloadItems(at: [indexPath])
        guard let cell = collectionView.cellForItem(at: indexPath) as? PhotosCell else { fatalError("Couldn't return a photo cell") }
        selectedImageView.image = cell.photoView.image
    }
}


class PhotosCell: UICollectionViewCell {

let photoView = UIImageView()
var checkmarkBannerImageView: UIImageView? 

override init(frame: CGRect) {
    super.init(frame: frame)
    addSubview(photoView)
    photoView.anchor(top: topAnchor, left: leadingAnchor, bottom: bottomAnchor, right: trailingAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
}

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

func setupCheckmarkBanner() {
    checkmarkBannerImageView = UIImageView(image: #imageLiteral(resourceName: "check").withRenderingMode(.alwaysTemplate))
    checkmarkBannerImageView?.contentMode = .center
    checkmarkBannerImageView?.contentScaleFactor = 4.0
    checkmarkBannerImageView?.tintColor = .white
    checkmarkBannerImageView?.setBottomBorder(for: .white)
    checkmarkBannerImageView?.convertToCircle(value: 12)

    photoView.addSubview(checkmarkBannerImageView!)
    checkmarkBannerImageView?.anchor(top: photoView.topAnchor, left: nil, bottom: nil, right: photoView.trailingAnchor, paddingTop: 4, paddingLeft: 0, paddingBottom: 0, paddingRight: 4, width: 24, height: 24)
}

func removeCheckmarkBanner() {
    checkmarkBannerImageView?.removeFromSuperview()
    checkmarkBannerImageView?.constraints.forEach{$0.isActive = false }
    checkmarkBannerImageView = nil
}
}

Answer 1

为了避免重复使用的单元格中出现不需要的内容，您可以重写prepareForReuse()方法，并在其中完成所有设置工作(例如隐藏复选标记)