Question

I have an iPhone app problem that’s been bugging me for a few days and it really doesn’t seem like it should be this difficult so I’m sure I’m missing something obvious. I have researched plenty of forum discussions on “similar” topics but nothing that actually addresses this issue, specifically.

To be clear, if there is some piece of documentation or some other source that I should research, please point me in the right direction.

Here goes…

I have a list of items that I display to the user within a table (uitableview). The cell (uitableviewcell) for each item is custom and contains an image and a Like button (uibutton). As expected, for each item in the the table, the user can click the Like button or ignore it. The like button calls a separate process to update the server. Simple, right?

So, here is the issue:

When the Like button is clicked on a particular cell, the Selected state works fine but the moment you scroll the cell out of view, other random cells in the table show the Like button as Selected even though they were never touched. Because the cells are reused, for obvious performance reasons, I understand why this could happen. What I don’t understand is why my approach (see code below) would not override or reset the button’s state the way I think it should. For brevity, I am only including the relevant code here (hopefully formatted properly):

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

if (cell == nil) {
    cell = [[MyCustomViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    cell.selectionStyle = UITableViewCellSelectionStyleNone;
}

    NSString *myRating = [[self.dataArray objectAtIndex:indexPath.row] valueForKey:@"my_rating"];

    // Create the Like button
    UIButton *likeButton = [[UIButton alloc] initWithFrame:CGRectMake(260, 68, 40, 40)];
    [likeButton setImage:[UIImage imageNamed:@"thumbsUp"] forState:UIControlStateNormal];
    [likeButton setImage:[UIImage imageNamed:@"thumbsUpSelected"] forState:UIControlStateSelected];
    if (myRating == @"9") {
        [likeButton setSelected:YES];
    }
    [likeButton setTitle:@"9" forState:UIControlStateNormal];
    [likeButton setTag:indexPath.row];
    [cell.contentView addSubview:likeButton];
    [likeButton addTarget:self action:@selector(likeButtonPressed:) forControlEvents:UIControlEventTouchUpInside];

    return cell;
}

- (void)likeButtonPressed:(UIButton *)sender {

    // Changed the Selected state on the button
    UIButton *button = (UIButton *)sender;
    button.selected = !button.selected;

    // Create a new object with the user's rating and then replace it in the dataArray
    NSString *ratingText = sender.titleLabel.text;    
    NSMutableArray *myMutableArray = [[self.dataArray objectAtIndex:row] mutableCopy];
    [myMutableArray setValue:ratingText forKey:@"my_rating"];
    [self.dataArray replaceObjectAtIndex:row withObject:myMutableArray];
}

So, I’ve been through many iterations of this but I can’t seem to get the state of the button to show the Selected image for those items that are Liked and keep the normal image for those items that have not been Liked.

Any help or advice would be greatly appreciated.

Answer 1

The problem is that every time you create or reuse a cell you’re giving it a new like button, so when you reuse a cell where the like button has been activated, you’re giving it a deactivated like button but the old, activated like button is still there as well.

Instead of creating a like button every time you need a cell, you should just be setting the state of an existing like button. See the answers to this question for some possible ways of handling that.