UITableview Scrolls to Top on Reload

问题:

I am facing problem in my app - you can post and edit your favorite places. After posting a post, or editing a specific post (UITableViewCell), UITableview is reloaded.

My problem is: the UITableview scrolls to the top after reloading. But that's not what I want. I want my view to stay on the cell / view where I was. But I don't know how to manage that.

Could you help me?

回答1:

Igor's answer is correct if you are using dynamically resizable cells (UITableViewAutomaticDimension)

Here it is in swift 3:

    private var cellHeights: [IndexPath: CGFloat?] = [:]
    var expandedIndexPaths: [IndexPath] = []

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

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


    func expandCell(cell: UITableViewCell) {
      if let indexPath = tableView.indexPath(for: cell) {
        if !expandedIndexPaths.contains(indexPath) {
            expandedIndexPaths.append(indexPath)
            cellHeights[indexPath] = nil
            tableView.reloadRows(at: [indexPath], with: UITableViewRowAnimation.automatic)
            //tableView.scrollToRow(at: indexPath, at: .top, animated: true)
        }
      }
    }

回答2:

To prevent scrolling to top, you should save heights of cells when they loads and give exact value in tableView:estimatedHeightForRowAtIndexPath:

// declare cellHeightsDictionary
NSMutableDictionary *cellHeightsDictionary;

// initialize it in ViewDidLoad or other place
cellHeightsDictionary = @{}.mutableCopy;

// save height
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    [cellHeightsDictionary setObject:@(cell.frame.size.height) forKey:indexPath];
}

// give exact height value
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSNumber *height = [cellHeightsDictionary objectForKey:indexPath];
    if (height) return height.doubleValue;
    return UITableViewAutomaticDimension;
}

回答3:

The UITableView's reloadData() method is explicitly a force reload of the entire tableView. It works well, but is usually jarring and a bad user experience if you're going to do that with a tableview that the user is currently looking at.

Instead, take a look at reloadRowsAtIndexPaths(_:withRowAnimation:) and reloadSections(_:withRowAnimation:) in the documentation.

回答4:

Just go for these lines if you want an easy solution

    let contentOffset = tableView.contentOffset
    tableView.reloadData()
    tableView.setContentOffset(contentOffset, animated: false)

回答5:

In swift 3.1

DispatchQueue.main.async(execute: {

    self.TableView.reloadData()
    self.TableView.contentOffset = .zero

})