Question

I am trying to add a button to a cell in my cellForRowAtIndexPath method. That works but I seem to be adding a button every time the cell is updated (discovered this because I have updated the wrong screen position and I have 2 buttons that both work and can be clicked).

When is the correct time to allocate and release a UIButton thats added to a cell? Surely I cannot release the button at the end of cellForRowAtIndexPath – that would destroy the button object wouldn’t it? All of the snippets I’ve found with buttons added to cells so far seem to keep instantiation new UIButton objects within cellForRowAtIndexPath which has me somewhat confused..

Answer 1

A couple of things:

1. Buttons are appearing elsewhere because you’re using the same cell identifier for different types of cells. Each type of cell should get it’s own identifier.

2. In terms of the button disappearing, I don’t know why that’s happening as a result of reloadRowsAtIndexPaths, but if you move the button to the front of the other subviews, you won’t lose it.

3. You probably want to autorelease your UITextField. (Same true with NSString in titleForHeaderInSection.)

Anyway, the cellForRowAtIndexPath becomes something like:

#define kTextFieldTag 100
#define kButtonFieldTag 101

//-----------------------------------------------------------------------------------------
// cellForRowAtIndexPath
//-----------------------------------------------------------------------------------------
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *cellIdentifier;
    UITableViewCell *cell;

    // Configure the cell...
    switch( [indexPath section] ) 
    {
        case WORKSHEET_SECTION_CLIENT: 
            cellIdentifier = @"CellClient";

            cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

            if (cell == nil) 
            {
                cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
            }

            cell.textLabel.text = clientName;
            cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;      
            break;

        case WORKSHEET_SECTION_PERIOD: 
        {
            UIButton *myButton1;

            cellIdentifier = @"CellPeriod";

            cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

            if (cell == nil) 
            {
                cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];

                // Don't need UIButton alloc because method below does it for us..
                myButton1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
                myButton1.tag = kButtonFieldTag;

                CGRect cellFrame = [self.tableView rectForRowAtIndexPath:indexPath];

                int nButtonWidth  = 80;
                int nButtonHeight = 30;
                int nActualCellWidth = cellFrame.size.width - 40;
                int nButtonDeltaX = ( nActualCellWidth      - nButtonWidth  ) / 2;
                int nButtonDeltaY = ( cellFrame.size.height - nButtonHeight ) / 2;
                myButton1.frame = CGRectMake( nButtonDeltaX, nButtonDeltaY, nButtonWidth, nButtonHeight );      

                [myButton1 setTitle:@"OK" forState:UIControlStateNormal];

                // PDS: Add delaget for stopwatch clicking..
                [myButton1 addTarget:self action:@selector(buttonClickedStopWatch:) forControlEvents:UIControlEventTouchUpInside];  

                [cell.contentView addSubview:myButton1];      
            }
            else
            {
                myButton1 = (UIButton *)[[cell contentView] viewWithTag:kButtonFieldTag];
            }

            cell.textLabel.text = timeElapsed;
            cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;   
            [[cell contentView] bringSubviewToFront:myButton1];

            break;      
        }

        case 2:
            cellIdentifier = @"Cell2";

            cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

            if (cell == nil) 
            {
                cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
            }

            cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
            cell.textLabel.text = @"Amount $130";
            break;      

        case 3:
        {
            cellIdentifier = @"Cell3";

            cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
            UITextField *myTextField;            

            if (cell == nil) 
            {
                cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];

                myTextField = [[[UITextField alloc] initWithFrame:CGRectMake(20,10,125,25)] autorelease];
                [myTextField setTag:kTextFieldTag];
                myTextField.adjustsFontSizeToFitWidth = NO;
                myTextField.backgroundColor = [UIColor clearColor];
                myTextField.autocorrectionType = UITextAutocorrectionTypeNo;
                myTextField.autocapitalizationType = UITextAutocapitalizationTypeWords;
                myTextField.textAlignment   = UITextAlignmentLeft;
                myTextField.keyboardType    = UIKeyboardTypeDefault;
                myTextField.returnKeyType   = UIReturnKeyDone;
                myTextField.clearButtonMode = UITextFieldViewModeNever;
                //      myTextField.delegate = self;
                myTextField.font = [UIFont systemFontOfSize:14];

                [cell addSubview:myTextField];
            }
            else
            {
                myTextField = (UITextField *)[[cell contentView] viewWithTag:kTextFieldTag];
            }

            // note, theoretically, you could blow away anything that the user typed here
            [myTextField setPlaceholder:@"Type Data Here"];          

            cell.accessoryType = UITableViewCellAccessoryNone;

            cell.textLabel.font = [UIFont systemFontOfSize:14];
            cell.textLabel.numberOfLines = 0;
            break;

        }

        default:
            cellIdentifier = @"CellDummy";

            cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

            if (cell == nil) 
            {
                cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
            }

            cell.textLabel.text = @"Dummy";
            break;

    }

    return cell;
}

Personally, I might split this into separate methods, but that’s up to you.