Reuse cell... :(

I have a table with 9 sections and 56 rows.

I want to add a text label for each cell. I created a NSArray menuList with 56 NSDictionaries and an array containing the number of rows in each section (sectionsArray).

Here is my code, but it doesn't work properly at all:

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    //Use existing cell (reusable)
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellIdentifier];

    //If no existing cell,开发者_开发问答 create a new one
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:kCellIdentifier] autorelease];

        //Define cell accessory type
        cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

        //Create a subView for the cell
        CGRect subViewFrame = cell.contentView.frame;
        subViewFrame.origin.x += kInset;
        subViewFrame.size.width = kInset + kSelectLabelWidth;

        UILabel *selectedLabel = [[UILabel alloc] initWithFrame:subViewFrame];

        //SubView design
        selectedLabel.textColor = [UIColor blackColor];
        selectedLabel.highlightedTextColor = [UIColor whiteColor];
        selectedLabel.backgroundColor = [UIColor clearColor];

        [cell.contentView addSubview:selectedLabel];

        int indRow = 0;
        for (int i =0; i < indexPath.section; i++) {
            indRow += [[sectionsArray objectAtIndex:i] intValue];
        }
        indRow += indexPath.row;

        NSDictionary *cellText = [menuList objectAtIndex:indRow];

        selectedLabel.text = [cellText objectForKey:@"selection"];
        [selectedLabel release];

    }
    return cell;        
}

What's wrong in this code?

In iOSSimulator, i see that cell's text change sometimes when I'm scrolling, and labels are not in the right order.

All the code that fills in your cells is with in the:

if (cell == nil) {

statement, so you end up creating a small number of cells and filling them in (when cell==nil) and then just return the dequeued ones.

This is what it should be:

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    //Use existing cell (reusable)
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellIdentifier];

    //If no existing cell, create a new one
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:kCellIdentifier] autorelease];

        //Define cell accessory type
        cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

        //Create a subView for the cell
        CGRect subViewFrame = cell.contentView.frame;
        subViewFrame.origin.x += kInset;
        subViewFrame.size.width = kInset + kSelectLabelWidth;

        UILabel *selectedLabel = [[UILabel alloc] initWithFrame:subViewFrame];

        //SubView design
        selectedLabel.textColor = [UIColor blackColor];
        selectedLabel.highlightedTextColor = [UIColor whiteColor];
        selectedLabel.backgroundColor = [UIColor clearColor];

        [cell.contentView addSubview:selectedLabel];
    }
    // At this point cell whether it is a reused cell or a new one
    // cell points to the object we need to fill in.

    int indRow = 0;
    for (int i =0; i < indexPath.section; i++) {
        indRow += [[sectionsArray objectAtIndex:i] intValue];
    }
    indRow += indexPath.row;

    NSDictionary *cellText = [menuList objectAtIndex:indRow];

    selectedLabel.text = [cellText objectForKey:@"selection"];
    [selectedLabel release];

    return cell;       
}

This is what the code is doing:

Try to get a reusable cell

If no reusable cell is available
{
    create a new cell
}

Fill in the values for the cell

So when a cell scrolls of the screen it is put into a reuse queue. When a cell is about to come onto the screen your cellForRowAtIndexPath is called. Allocating a new cell is slower than reusing an existing one, so you first try to get a cell from the reuse queue, but if one is not available you create a new one. Then you fill in your values.