Question

I am trying to create a list of options with check boxes. I am using UITableView and adding custom type buttons to the table as checkboxes.

My code for cellForRowAtIndexPath method is pasted below:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
CGRect a=CGRectMake(0, 0, 310, 32);
UIImageView *aImg=[[UIImageView alloc] initWithFrame:a];
UIImageView *bImg=[[UIImageView alloc] initWithFrame:a];
aImg.image=[[[Resources getResources] getImageLoader] getMainMenuUnselectedImage];
bImg.image=[[[Resources getResources] getImageLoader] getLiveScoreSmallBg];
[aImg setContentMode:UIViewContentModeScaleToFill];
[bImg setContentMode:UIViewContentModeScaleToFill];
cell.backgroundView = [[UIView alloc] initWithFrame:a];
[cell.backgroundView addSubview:aImg];
cell.selectedBackgroundView=bImg;
cell.font = [UIFont boldSystemFontOfSize:16];
cell.selectedTextColor = [UIColor blackColor];
UIImage *checked = [UIImage imageNamed:@"check_filled.png"];
UIImage *unchecked = [UIImage imageNamed:@"check_empty.png"];
UIButton *button = [[UIButton buttonWithType:UIButtonTypeCustom] initWithFrame:CGRectMake(3, 3, 30, 30)];
[button addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];
[button setImage: [UIImage imageNamed:@"check_filled.png"] forState: UIControlStateSelected];
[button setImage: [UIImage imageNamed:@"check_empty.png"] forState: UIControlStateNormal];
[button setEnabled:YES];
button.tag = indexPath.row;
[button setUserInteractionEnabled:YES];
[cell.contentView addSubview:button];

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(40, 3, 250, 17)];
label.font = [UIFont boldSystemFontOfSize:15]; 
label.backgroundColor = [UIColor clearColor];
label.text = [teamsList objectAtIndex:indexPath.row];
[cell.contentView addSubview:label];

    [button release];
[label release];
[aImg release];
[bImg release];

return cell;
}

The problem is that when I run the program, the screen appears without buttons. Also, when I click any row, the program crashes.

Answer 1

There’re some problems with your code which may be not relevant to your problem, but still…

1. You create cell contents each time cell is reused – so if you scroll your table back and forth the reused cells will contain multiple identical subviews – that’s not what you want. To fixed that you must move creating contents to the creating cell block:

   if (cell == nil) {
       cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
       // Create cell contents here!
       ...
   }
   ...
   

2. You must not release your button – since you create it with convenience method button is autoreleased

   button = [[UIButton buttonWithType:UIButtonTypeCustom] 
                        initWithFrame:CGRectMake(3, 3, 30, 30)];
   

3. This line may also cause problems:

   [button addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];
   

   Here you set selector that receives no parameters. If your buttonPressed method declared is (most common way)

   - (void) buttonPressed:(id)sender;
   

   Then you must create selector as @selector(buttonPressed:) to indicate that it actually takes 1 parameter