Question

I have a tableView where I add UILabel’s to cell contentView as subview in cellForRowAtIndexPath method like this:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *CellIdentifier = @"ReuseCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if(cell == nil ){
    cell =[[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
}
// Code to remove labels overlay
for(UIView* view in cell.contentView.subviews){
    if ([view isKindOfClass:[UIView class]]) {
        [view removeFromSuperview];
    }
}
if ([indexPath row]<[itemsArray count]){
    UILabel* label1 = [[UILabel alloc] initWithFrame:CGRectMake(10,18,280,10)];
    label1.text = [NSString stringWithFormat:@"Description %@",[[itemsArray objectAtIndex:[indexPath row]] valueForKey:@"Desc"]];
            label1.font = [UIFont fontWithName:@"Helvetica" size:14];
    [cell.contentView addSubview:label1];
    [label1 release];

    UILabel *label2 = [[UILabel alloc] initWithFrame:CGRectMake(10,25,280,10)];
    label2.text = [NSString stringWithFormat:@"Price %@",[[itemsArray objectAtIndex:[indexPath row]] valueForKey:@"Price"]];
    label2.font = [UIFont fontWithName:@"Helvetica" size:14];
    [cell.contentView addSubview:label2];
    [label2 release];

    UILabel *label3 = [[UILabel alloc] initWithFrame:CGRectMake(10,40,290,11)];
    label3.text = [NSString stringWithFormat:@"Loc %@",[[itemsArray objectAtIndex:[indexPath row]] valueForKey:@"Loc"]];
    label3.font = [UIFont fontWithName:@"Helvetica" size:14];
    [cell.contentView addSubview:label3];
    [label3 release];
}
return cell;

}

When I scroll table view UILabels overlap on previous one’s because of cell reuse so I remove it using:

// Code to remove labels overlay
    for(UIView* view in cell.contentView.subviews){
        if ([view isKindOfClass:[UIView class]]) {
            [view removeFromSuperview];
        }

Which is why my scrolling is not so smooth if there are many rows to display. How to make my scrolling smooth ?

Answer 1

Don’t remove the labels: reuse them. If you give each one a tag, you can retrieve them using the content view’s -viewWithTag: and just change their text.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"ReuseCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    UILabel *label1;
    UILabel *label2;
    UILabel *label3;
    if( cell == nil )
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];

        label1 = [[UILabel alloc] initWithFrame:CGRectMake(10,18,280,10)];
        label1.font = [UIFont fontWithName:@"Helvetica" size:14];
        label1.tag = 1;
        [cell.contentView addSubview:label1];
        [label1 release];

        label2 = [[UILabel alloc] initWithFrame:CGRectMake(10,25,280,10)];
        label2.font = [UIFont fontWithName:@"Helvetica" size:14];
        label2.tag = 2;
        [cell.contentView addSubview:label2];
        [label2 release];

        label3 = [[UILabel alloc] initWithFrame:CGRectMake(10,40,290,11)];
        label3.font = [UIFont fontWithName:@"Helvetica" size:14];
        label3.tag = 3;
        [cell.contentView addSubview:label3];
        [label3 release];
    }
    else
    {
        // retrieve the labels using the tags you defined earlier

        label1 = (UILabel *)[cell.contentView viewWithTag:1];
        label2 = (UILabel *)[cell.contentView viewWithTag:2];
        label3 = (UILabel *)[cell.contentView viewWithTag:3];
    }

    if ( [indexPath row] < [itemsArray count] )
    {
        NSDictionary *item = [itemsArray objectAtIndex:[indexPath row]];
        label1.text = [NSString stringWithFormat:@"Description %@", [item valueForKey:@"Desc"]];
        label2.text = [NSString stringWithFormat:@"Price %@", [item valueForKey:@"Price"]];
        label3.text = [NSString stringWithFormat:@"Loc %@", [item valueForKey:@"Loc"]];
    }

    return cell;
}