CODEWITHSUNDEEP
iosobjective-cuitableview
TonyTony
TonyTony

Reputation: 1404

UITableView, another cell in invisible area has a checkmark while one in visible area is touched

This is my code, which shows a problem for 14 rows of a table view. For one screen, 6 cells are visible.

When I tapped the 2nd cell, the 10 cell also has a checkmark, tap 3rd then 11th checkmarked, 1st then 9th checkmarked, tap 1st, then 8th also checkmarked...but the grey highlight does not behave like this, only one cell can be highlighted.

If I tap a cell after one is tapped on the the same screen, the one just checkmarked will be cleared for checkmark, which makes sense. However, if after I tapped one cell and then scroll the tableview lower, I can tap a cell and it shows checkmark as well, i.e. the one just checked on top screen still has a checkmark. So if I scroll up and down, and tap one cell each time after I scroll to the other side, I can put a checkmark for every cell, all checkmarks are shown.

It is really weird, and I have tried a lot of ways to solve it, but seems I have some basic understanding of UITableView missing, can anyone figure it out, please? Thanks.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *ID= @"UITableViewCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:ID];
    }

    cell.imageView.image = [UIImage imageNamed:@"earth.png"];

    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath   *)indexPath
{
    UITableViewCell *cell =[tableView cellForRowAtIndexPath:indexPath];    
    cell.accessoryType = UITableViewCellAccessoryCheckmark;
}

-(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell =[tableView cellForRowAtIndexPath:indexPath];
    cell.accessoryType = UITableViewCellAccessoryNone;
}

Upvotes: 2

Views: 671

Answers (2)

UtkuS
UtkuS

Reputation: 234

Stonz2's answer is right. For example, you should create an object for table view data source and it should has a property to show is it checkmarked.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:     (NSIndexPath *)indexPath
{
    ...

    Item *item = [self.itemArray objectAtIndex:indexPath.row];
    if (item.checkmarked) {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    } else {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }

}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:NO];
    Item *tappedItem = [self.itemArray objectAtIndex:indexPath.row];
    tappedItem.checkmarked = !tappedItem.checkmarked;
    [tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];


}

Upvotes: 1

Stonz2
Stonz2

Reputation: 6396

You're not storing the existence/absence of your checkmark in any sort of persisted data source and showing/hiding it in cellForRowAtIndexPath. Because of this, your table is reusing your cells, and it just throws it up as it found it. So if it reuses a cell that had your checkmark accessory enabled, it shows it as enabled (because you didn't specifically disable it in cellForRow)

I would keep an NSMutableArray of selected indexPath objects. Add the indexPath in didSelectRowAtIndexPath, and remove it in didDeselectRowAtIndexPath. Then, in cellForRowAtIndexPath, check if the current indexPath exists in the array and enable the checkmark if so, disable if not.

Upvotes: 5

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