UITableView 最后一行的 indexPath

Question

I am attempting to make the last row in a UITableView visible, after it has been added. Right now, when I add a row and call reloadData, the table goes to the top.

I figure if I get the indexPath for the last row, that I can select that row and it should appear in the list. I am unsure of how to get that value, or even if I am approaching this correctly.

How do I get an indexPath for a specific row?

Answer 1

Please note that, you don't need to call the reloadData to make the last row visible. You can make use of scrollToRowAtIndexPath method.

You can use the below code to achieve your goal.

// First figure out how many sections there are
let lastSectionIndex = self.tblTableView!.numberOfSections() - 1

// Then grab the number of rows in the last section
let lastRowIndex = self.tblTableView!.numberOfRowsInSection(lastSectionIndex) - 1

// Now just construct the index path
let pathToLastRow = NSIndexPath(forRow: lastRowIndex, inSection: lastSectionIndex)

// Make the last row visible
self.tblTableView?.scrollToRowAtIndexPath(pathToLastRow, atScrollPosition: UITableViewScrollPosition.None, animated: true)

Swift 4.0:

tableView.scrollToRow(at: indexPath, at: UITableViewScrollPosition.none, animated: true)

Answer 2

You can use scrollToRowAtIndexPath with extension:

In Swift 3:

extension UITableView {
    func scrollToLastCell(animated : Bool) {
        let lastSectionIndex = self.numberOfSections - 1 // last section
        let lastRowIndex = self.numberOfRows(inSection: lastSectionIndex) - 1 // last row
        self.scrollToRow(at: IndexPath(row: lastRowIndex, section: lastSectionIndex), at: .Bottom, animated: animated)
    }
}

Answer 3

Shamsudheen TK's answer will crash

if there is no rows/sections in tableview.

The following solution to avoid crash at run time

extension UITableView {
  func scrollToBottom() {

    let lastSectionIndex = self.numberOfSections - 1
    if lastSectionIndex < 0 { //if invalid section
        return
    }

    let lastRowIndex = self.numberOfRows(inSection: lastSectionIndex) - 1
    if lastRowIndex < 0 { //if invalid row
        return
    }

    let pathToLastRow = IndexPath(row: lastRowIndex, section: lastSectionIndex)
    self.scrollToRow(at: pathToLastRow, at: .bottom, animated: true)
  }
}

Note: If you are trying to scroll to bottom in block/clousure then you need to call this on main thread.

DispatchQueue.main.async {
  self.tableView.scrollToBottom()
}

Hope this will helps other

Answer 4

As suggested by others get indexPath for perticular sections like section 0.

After that call...add this methos in cellFOrROwAtIndex

[tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:YES]; ..to scroll to specific indexPath in TableView.

Note:-But it still need scrolling of tableview in Downward direction.

Answer 5

You shouldn't be using -reloadData for this use case. What you're looking for is -insertRowsAtIndexPaths:withRowAnimation: .

Feel free to ask if you want some usage examples or a more detailed explanation as to why using -reloadData send you to the top of the UITableView .

Answer 6

Not mandatorily required to get the indexpath of last row.
You can set the CGPoint of UITableview to show a last row you added.
I always use this code in my chat application to show a last added message.

//Declaration
@IBOutlet weak var tableview: UITableView!

//Add this executable code after you add this message.
var tblframe: CGRect = tableview.frame
tblframe.size.height = self.view.frame.origin.y
tableview.frame = tblframe
var bottomoffset: CGPoint = CGPointMake(0, tableview.contentSize.height - tableview.bounds.size.height)
if bottomoffset.y > 0 {
    tableview.contentOffset = bottomoffset;
}

I hope it will work for you.
Thanks.

Answer 7

Swift 5.0 +

 extension UITableView {
    func isLastVisibleCell(at indexPath: IndexPath) -> Bool {
        guard let lastIndexPath = indexPathsForVisibleRows?.last else {
            return false
        }
        return lastIndexPath == indexPath
    }
}