Why does this button on my UITableView cell repaint itself?

I have a button on my tableview cell.

But after scrolling the buttons look like this:

It looks like there is sometimes one button above the other.

How can I solve this problem?

That's my code for the button in cellForRowAtIndexPath

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

Chapter *chapter = nil ;
UITableViewCell *cell = nil;
NSUInteger row = [indexPath row];
switch (indexPath.section) {
    case 0: 
        chapter = [[einfuerung objectAtIndex:row]retain];
        break;
    case 1: 
        chapter = [[vertiefung objectAtIndex:row]retain];
        break;
    case 2: 
        chapter = [[spezial objectAtIndex:row]retain];
        break;
}


if ([self filesFromFolderWithChapter:chapter] > 1) 
{

    static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
    cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier];
    if (cell == nil) 
    { 
        cell = [[[UITableViewCell alloc]
                initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:SimpleTableIdentifier] autorelease];
    }
}   
else {

    static NSString *ButtonTableIdentifier = @"ButtonTableIdentifier";
    cell = [tableView dequeueReusableCellWithIdentifier: ButtonTableIdentifier];
    if (cell == nil) 
    { 
        cell = [[[UITableViewCell alloc]
                initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:ButtonTableIdentifier] autorelease];
    }

}



    NSString *firstString;
    NSString *lastString;

    switch (indexPath.section) {
        case 0: 
            chapter = [[einfuerung objectAtIndex:row]retain];
            [dataInstance extractFromString: [chapter title]: &firstString: &lastString];
            cell.textLabel.text = firstString; 
            cell.detailTextLabel.text = lastString;
            cell.backgroundColor = [UIColor whiteColor];


            break;
        case 1: 
            chapter = [[vertiefung objectAtIndex:row]retain];
            [dataInstance extractFromString: [chapter title]: &firstString: &lastString];
            cell.textLabel.text = firstString; 
            cell.detailTextLabel.text = lastString;
            cell.backgroundColor = [UIColor whiteColor];

            break;
        case 2: 
            chapter = [[spezial objectAtIndex:row]retain];
            [dataInstance extractFromString: [chapter title]: &firstString: &lastString];
            cell.textLabel.text = firstString; 
            cell.detailTextLabel.text = lastString;
            cell.backgroundColor = [UIColor whiteColor];

            break;
    }



if ([self filesFromFolderWithChapter:chapter] > 1) 
{


        //VersionButton *button = [VersionButton buttonWithType:UIButtonTypeRoundedRect];
        VersionButton *button = [[VersionButton alloc]initWithFrame:CGRectMake(500, 15, 150, 30) andTitle:@"ältere Versionen"];
        button.chapter = chapter;
        [button addTarget:self action:开发者_JAVA技巧@selector(versionTapped:) 
         forControlEvents:UIControlEventTouchUpInside];
        [cell.contentView addSubview:button];   
        [button release];

}
    [chapter release];

return cell;

}

First of all it would be helpful to see your entire cellForRowAtIndexPath function.

It looks like you are not accounting for cell reuse correctly. You should only add a button to your cell if you are creating a cell from scratch and not if a cell is being reused. If a cell is being reused you should have a way to access the button it already has and make any changes necessary to it.

are you calling setNeedsDisplay somewhere else that would cause it to call the drawRect?