scrollToRowAtIndexPath始终从顶部滚动而不是从当前偏移滚动

Question

在我的UITableView使用方法滚动到最后一个单元格:

WLNetworkClient.sharedClient().createCommentWIthText(commentTextView.text, forItem: item) { error in

    defer {
        UIAlertController.showAlertFromError(error)
    }

    if error == nil {
        self.fetchedResultsController.fetchRequest.fetchLimit += 1
        try! self.fetchedResultsController.performFetch()
        self.tableView.reloadData()
        self.scrollTableViewToBottom()
    }
}

private func scrollTableViewToBottom() {

    tableView.scrollToRowAtIndexPath(NSIndexPath(forRow: fetchedResultsController.fetchedObjects!.count - 1, inSection: 0), atScrollPosition: UITableViewScrollPosition.Bottom, animated: true)
}

但是这没有按预期工作,因为ALWAYS表从顶部滚动,即使我在第二个单元格上也是如此.如何解决这个问题？

Answer 1

dosdos回答在Swift 2中为我工作 添加了一些小更新

宣布伊娃

var heightAtIndexPath = NSMutableDictionary()

在func viewDidLoad()中

func viewDidLoad() {
  .... your code
  self.tableView.rowHeight = UITableViewAutomaticDimension
}

然后添加以下两种方法:

override func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
   let height = self.heightAtIndexPath.objectForKey(indexPath)
   if ((height) != nil) {
     return CGFloat(height!.floatValue)
   } else {
    return UITableViewAutomaticDimension
   }
 }

override func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
  let height = cell.frame.size.height
  self.heightAtIndexPath.setObject(height, forKey: indexPath)
}

SWIFT 3:

var heightAtIndexPath = NSMutableDictionary()

func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
    let height = self.heightAtIndexPath.object(forKey: indexPath)
    if ((height) != nil) {
        return CGFloat(height as! CGFloat)
    } else {
        return UITableViewAutomaticDimension
    }
}

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    let height = cell.frame.size.height
    self.heightAtIndexPath.setObject(height, forKey: indexPath as NSCopying)
}