获取CollectionView中所有collectionViewCells高度的总和

// 获取CollectionView中所有collectionViewCells高度的总和
func getTotalCellHeight() -> CGFloat {
    var totalHeight: CGFloat = 0
    
    guard let collectionView = collectionView else {
        return totalHeight
    }
    
    let numberOfSections = collectionView.numberOfSections
    for section in 0..<numberOfSections {
        let numberOfItems = collectionView.numberOfItems(inSection: section)
        for item in 0..<numberOfItems {
            let indexPath = IndexPath(item: item, section: section)
            if let cell = collectionView.cellForItem(at: indexPath) {
                // 获取cell的高度
                let cellHeight = cell.frame.height
                totalHeight += cellHeight
            }
        }
    }
    
    return totalHeight
}