Images getting mixed up in a UITableView - XML parsing

Question

EDIT: Actually images appear fine, it's when I scroll that they get mixed up...

I'm parsing an XML file with links to images which I'm putting into a UITable. For some reason the pictures are getting completely mixed up and when I scroll down the table some of them even start to change! Here's the code I'm using for my UITable:

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

    static NSString *CellIdentifier = @"Cell";
    Tweet *currentTweet = [[xmlParser tweets] objectAtIndex:indexPath.row];

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];

        CGRect imageFrame = CGRectMake(2, 8, 40, 40);
        customImage = [[UIImageView alloc] initWithFrame:imageFrame];
        [cell.contentView addSubview:customImage];

    }

    NSString *picURL = [currentTweet pic];
    if (![picURL hasPrefix:@"http:"]) {
        picURL = [@"http:" stringByAppendingString:picURL];
    }

    customImage.image = [UIImage imageWithData:[NSData dataWithContentsOfURL: [NSURL URLWithString:picURL]]];

    return cell;
}

Any idea what I'm doing wrong? Any help is seriously appreciated. Thx!

score 3 · Accepted Answer · answered Jan 21 '13 at 14:48

Your problem is that if the cell is not nil (i.e. you've successfully reused a cell that has scrolled off the screen), you're not setting the customImage pointer properly (since it is a class instance variable, it has the value from the last cell it created). So, define some non-zero constant for kCustomImageTag and then modify the if statement in cellForRowAtIndexPath to be:

if (cell == nil)
{
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];

    CGRect imageFrame = CGRectMake(2, 8, 40, 40);
    customImage = [[UIImageView alloc] initWithFrame:imageFrame];
    [cell.contentView addSubview:customImage];
    customImage.tag = kCustomImageTag;
}
else
{
    customImage = [cell.contentView viewWithTag:kCustomImageTag];
}

Set the tag when you create customImage and use that tag to retrieve an existing customImage in the reused UITableViewCell.

score 0 · Answer 2 · answered Jan 21 '13 at 14:11

when you ask for a reusable cell, if it's not nil it is a cell that you already allocated and added subviews to it's contentView... you should remove all subviews first in you cellForRow..

if (cell == nil)
{
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];

    CGRect imageFrame = CGRectMake(2, 8, 40, 40);
    customImage = [[UIImageView alloc] initWithFrame:imageFrame];
    [cell.contentView addSubview:customImage];

}  else {
     for (UIView *v in cell.contentView)
          [v removeFromSuperView];
}

score 0 · Answer 3 · answered Jan 21 '13 at 14:14

0

Have a look at this project: https://github.com/bharris47/LIFOOperationQueue

It shows how you can load images in the background with using an NSTable. Additionally, it should be a pretty good of how to not get your images mix-matched.

answered Jan 21 '13 at 14:14

user1997259

11
2

Images getting mixed up in a UITableView - XML parsing

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