How to go to the next/previous cell in UITableView programmatically?

Question

I've got UItableview and also two buttons Next and Previous tapping on which I should go to the selection of the previous/next cell? is it possible? Moreover, how to remember the cell the user last tapped so that it is selected on start-up?

Answer 1

Implement UITableViewDelegate and save the currently selected index in didSelectRowAtIndexPath:

NSIndexPath *currentSelection;

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    currentSelection = indexPath;
}

Then in your button action you can do something like...

- (IBAction)didTapNextButton:(id)sender{

    //Remember to check boundaries before just setting an indexpath or your app will crash!
    if(currentSelection){
        currentSelection = [NSIndexPath indexPathForRow:currentSelection.row+1 inSection:currentSelection.section];
    }else{
        currentSelection = [NSIndexPath indexPathForRow:0 inSection:0];
    }

    [self.tableView selectRowAtIndexPath:currentSelection animated:YES scrollPosition: UITableViewScrollPositionTop];

}

Answer 2

Here are a couple of UITableView category methods that can find the next/previous NSIndexPath from a specified NSIndexPath.

These methods accommodate sections and empty sections.

@interface (.h)

@interface UITableView(Extensions)
- (NSIndexPath *)nextIndexPathFromIndexPath:(NSIndexPath *)indexPath;
- (NSIndexPath *)prevIndexPathFromIndexPath:(NSIndexPath *)indexPath;
@end

@implementation (.m)

@implementation UITableView(Extensions)
-(NSIndexPath *)nextIndexPathFromIndexPath:(NSIndexPath *)indexPath {
    return [self adjacentIndexPathFromIndexPath:indexPath goingForward:YES];
}

-(NSIndexPath *)prevIndexPathFromIndexPath:(NSIndexPath *)indexPath {
    return [self adjacentIndexPathFromIndexPath:indexPath goingForward:NO];
}

-(NSIndexPath *)adjacentIndexPathFromIndexPath:(NSIndexPath *)indexPath goingForward:(BOOL)goingForward {
    NSInteger delta = goingForward ? 1 : -1;

    NSInteger adjRow = indexPath.row + delta;

    if (adjRow >= 0 && adjRow < [self numberOfRowsInSection:indexPath.section]) {
        //Adjacent row in same section...
        return [NSIndexPath indexPathForRow:adjRow inSection:indexPath.section];
    }

    NSInteger adjSection = indexPath.section + delta;

    if (adjSection < 0) {
        adjSection = [self numberOfSections] - 1;
    } else if (adjSection > [self numberOfSections] - 1) {
        adjSection = 0;
    }

    NSUInteger adjSectionRows = [self numberOfRowsInSection:adjSection];

    if (!adjSectionRows) {
        //Adjacent section is empty...
        //Adjacent row in adjacent-adjacent section...
        return [self adjacentIndexPathFromIndexPath:[NSIndexPath indexPathForRow:0 inSection:adjSection] goingForward:goingForward];
    }

    adjRow = goingForward ? 0 : adjSectionRows - 1;

    //Adjacent row in adjacent section...
    return [NSIndexPath indexPathForRow:adjRow inSection:adjSection];
}

@end