a simple question but I don't seem to have the right terminology to search Stackoverflow by it.
I have a UITableView with no sections, the user can scroll up and down a long list of data (rows) presented inside this tableview.
Question: how can I detect the most top cell row number after the user scrolled. (for example, if the user is scrolling 30 cells down, the top cell after the scroll is = 30)
You could try using UITableView
's -indexPathsForVisibleRows
or -indexPathForRowAtPoint
.
For example, let's say that you want to print the indexPath of the topmost visible cell, when you stop dragging your table. You could do something like this:
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
NSIndexPath *firstVisibleIndexPath = [[self.tableView indexPathsForVisibleRows] objectAtIndex:0];
NSLog(@"first visible cell's section: %i, row: %i", firstVisibleIndexPath.section, firstVisibleIndexPath.row);
}
For Swift 3.0
let topVisibleIndexPath:IndexPath = self.tableView.indexPathsForVisibleRows![0]
You get the index paths for the visible rows
NSArray* indexPaths = [tableView indexPathsForVisibleRows];
Then sort using compare:
NSArray* sortedIndexPaths = [indexPaths sortedArrayUsingSelector:@selector(compare:)];
Then get the first element's row
NSInteger row = [(NSIndexPath*)[sortedIndexPaths objectAtIndex:0] row];
This is the Swift 3+ code:
override func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
let firstVisibleIndexPath = self.tableView.indexPathsForVisibleRows?[0]
print("First visible cell section=\(firstVisibleIndexPath?.section), and row=\(firstVisibleIndexPath?.row)")
}
In Swift 4:
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let firstVisibleIndexPath = self.tableview.indexPathsForVisibleRows?[0]
print("top visible cell section is \([firstVisibleIndexPath!.section])")
}
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