How to keep UITableView contentoffset after calling -reloadData

Question

CGPoint offset = [_table contentOffset];
[_table reloadData];
[_table setContentOffset:offset animated:NO];    //unuseful

//    __block UITableView *tableBlock = _t         


        

Answer 1

Swift 4 variant of @Skywalker answer:

fileprivate var heightDictionary: [IndexPath: CGFloat] = [:]

override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    heightDictionary[indexPath] = cell.frame.size.height
}

override func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
    let height = heightDictionary[indexPath]
    return height ?? UITableViewAutomaticDimension
}

---

Another solution (fetched from MessageKit):

This method should be called instead of reloadData. This can fit for specific cases.

public func reloadDataAndKeepOffset() {
    // stop scrolling
    setContentOffset(contentOffset, animated: false)
        
    // calculate the offset and reloadData
    let beforeContentSize = contentSize
    reloadData()
    layoutIfNeeded()
    let afterContentSize = contentSize
        
    // reset the contentOffset after data is updated
    let newOffset = CGPoint(
        x: contentOffset.x + (afterContentSize.width - beforeContentSize.width),
        y: contentOffset.y + (afterContentSize.height - beforeContentSize.height))
    setContentOffset(newOffset, animated: false)
}