UITableViewCell不显示内容

Question

I am using Xcode 5, and developing an app targeted to iOS6/7.

In my storyboard, the "prototype cells", that refer to custom class "ObjListCell", derived from "UITableViewCell", contains a "Content View" that in turn contains a UIImageView and two UILabel elements. All three of them are connected to an IBOutlet in my ObjListCell class.

The table view controller refers to my custom class "ObjListViewController", derived from "UITableViewController". When this view controller is created, I have already retrieved the data, so in the viewDidLoad i call [self.tableView reloadData]; right away. But before doing so, i register the cell class: [self.tableView registerClass: [ObjListCell class] forCellReuseIdentifier:@"objTableCell"]; and "objTableCell" is set in the storyboard as the identifier for the cells.

Method numberOfRows in section returns 14, and I actually see a list with 14 empty rows on my iPhone. As I can see from the logs, method cellForRowAtIndexPath is actually called, and method dequeueReusableCellWithIdentifier returns a non-nil cell. So I set the icon and label content:

cell.mCellIcon.image = icon;
cell.mCellTitle.text = title;
cell.mCellExtra.text = extra;

I am sure the icon and text are OK, because I log them just before assigning them. But nevertheless, my table cells appear empty.

Can anyone suggest where the problem could be?

This is the whole code for cellForRowAtIndexPath:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"objTableCell";
    ObjListCell* cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];
    if (cell == nil)
        NSLog(@"ObjListViewController ERROR: Cell is nil");

    // Retrieve obj for this cell
    Obj* obj = [mObjs objectAtIndex:indexPath.row];
    if (obj == nil)
        NSLog(@"ObjListViewController ERROR: Obj not found for cell; indexPath = %i", indexPath.row);
    NSLog(@"ObjListViewController DEBUG: title = %@, extra = %@", obj.mTitle, obj.mExtra);

    // Set cell icon
    UIImage *icon = [mIcons iconForId:obj.mId andSize:@"big" withDefault:@"defaultIcon"];
    if (icon == nil)
        NSLog(@"ObjListViewController ERROR: Icon not found for cell; indexPath = %i", indexPath.row);
    cell.mCellIcon.image = icon;

    // Set cell title and extra
    cell.mCellTitle.text = obj.mTitle;
    if (obj.hasExtra)
        cell.mCellExtra.text = obj.mExtra;
    NSLog(@"ObjListViewController DEBUG: Inspecting cell content; icon = %@, title = %@, extra = %@",
     (cell.mCellIcon.image != nil ? @"OK" : @"nil"), cell.mCellTitle.text, cell.mCellExtra.text);

    // Standard accessory symbol
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    return cell;
}

And this is a excerpt of the log:

2014-02-16 15:21:06.665 trekking-etc-viewer[2671:60b] ObjListViewController DEBUG: title = Valle d'Aosta, extra = 
2014-02-16 15:21:06.668 trekking-etc-viewer[2671:60b] ObjListViewController DEBUG: Inspecting cell content; icon = nil, title = (null), extra = (null)
2014-02-16 15:21:06.685 trekking-etc-viewer[2671:60b] ObjListViewController DEBUG: title = Provincia di Belluno, extra = 
2014-02-16 15:21:06.690 trekking-etc-viewer[2671:60b] ObjListViewController DEBUG: Inspecting cell content; icon = nil, title = (null), extra = (null)

None of the "ERROR" log lines appear in the log.

Answer 1

I would suggest placing [self.tableView reloadData] in viewWillAppear: as the tableView may not be available yet in viewDidload:.

Also, if I am having problems like this, I will give my objects borders to see if they are actually placed where I expect them to be:

label.layer.borderWidth = 1.0f;
label.layer.borderColor = [UIColor greenColor].CGColor;

How about trying the following in cellForRowAtIndexPath:

static NSString *CellIdentifier = @"objTableCell";

ObjListCell *cell = (ObjListCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (!cell)
{
    cell = [[DDTripCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}

Answer 2

I am definitely unable to make it work using a storyboard, despite the many suggestions and attempts. For sure I am missing some little tricky detail somewhere, but tools don't provide any useful help on the matter. So I reverted to NIBs, and so this is my answer for the moment.

I would like just to summarize the few things I have taken care not to miss in defining and using the cell's nib:

• In the NIB, set the table view controller as the file's owner
• In the NIB, set the cell identifier to the proper value (objListCell, for me)
• In the NIB, connect each UI element to an IBOutlet in the cell's .h file
• In the cell's .m file, perhaps synthesise the outlets, but if you don't, it works all the same
• In viewWillAppear of the table's .m file, register the NIB (see details below)
• In cellForRowAtIndexPath of the table's .m file, dequeue your cell (see details below)

Registering the nib:

UINib* cellNib = [UINib nibWithNibName:@"ObjListCell" bundle:nil];
[self.tableView registerNib:cellNib forCellReuseIdentifier:@"objListCell"];

Dequeueing the cell:

static NSString *cellIdentifier = @"objListCell";
ObjListCell* cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];

All the rest is just as usual.