UITableView -headerViewForSection returns (null)

Question

I have a UITableView with 2 sections. Each with it's own headerView.
I have created a custom headerView via the -viewForHeaderInSection: method.
Later, I plan to modify it a bit so I need to use the viewForHeader method but I am unable to access the headerView and it's subViews.

As a simple example, I'm trying to NSLog the viewForHeader object in the -didSelectRowAtIndexPath: but I get a (null) result.

Sample Code:

-(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
    return 75;
}

-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{    
    UIView *myHeader = [[UIView alloc] init];
    switch (section) {
        case 0:
            [myHeader setBackgroundColor:[UIColor greenColor]];
            break;
        case 1:
            [myHeader setBackgroundColor:[UIColor redColor]];
            break;
        default:
            break;
    }

    UILabel *myLabel = [[UILabel alloc] init];
    [myLabel setFrame:CGRectMake(10, 0, 100, 30)];
    [myLabel setTag:101];
    [myLabel setBackgroundColor:[UIColor clearColor]];
    [myLabel setText:[NSString stringWithFormat:@"Section: %d",section]];

    [myHeader addSubview:myLabel];    
    return myHeader;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewHeaderFooterView *testView = [self.tableView headerViewForSection:indexPath.section];
    NSLog(@"%@",testView);  //displays (null)
}

---

Do I need to create the custom UIView xib as the headerView? (because as per a similar question and as per the docs")

To make the table view aware of your header or footer view, you need to register it.
You do this using the registerNib:forCellReuseIdentifier: or
registerClass:forCellReuseIdentifier: method of UITableView.

Answer 1

METHOD 1:

Ok, after some trial and error, I finally solved my own dilemma.
I did the headerView just as I would do a cell.

For a cell we would take UITableViewCell and use dequeueReusableCellWithIdentifier
while...
For a Header/Footer, we will take UITableViewHeaderFooterView and use the dequeueReusableHeaderFooterViewWithIdentifier method.

The rest is pretty much the same concept as a cell.

Prerequisites:

1. Set header height to 40
2. Set number of sections to 2 or more
3. Set number of rows per section to be atleast 1
4. iOS6+ (UITableViewHeaderFooterView won't work with iOS5 and below)

---

First Approach:

Creating and using the default UITableViewHeaderFooterView within -viewForHeaderInSection: method:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    static NSString *HeaderIdentifier = @"header";

    UITableViewHeaderFooterView *myHeader = [tableView dequeueReusableHeaderFooterViewWithIdentifier:HeaderIdentifier];
    if(!myHeader) {
        myHeader = [[UITableViewHeaderFooterView alloc] initWithReuseIdentifier:HeaderIdentifier];
    }

    UIButton *btnUp = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btnUp setTag:101];
    [btnUp setTitle:@"-" forState:UIControlStateNormal];
    [btnUp setFrame:CGRectMake(tableView.frame.size.width - 35, 5, 30, 30)];
    [myHeader addSubview:btnUp];

    [myHeader.textLabel setText:[NSString stringWithFormat:@"Section: %d",section]];

    [myHeader setFrame:CGRectMake(0, 0, tableView.frame.size.width, 50)];
    return myHeader;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewHeaderFooterView *theHeaderView = [tableView headerViewForSection:indexPath.section];
    NSLog(@"%@",theHeaderView); // -- great! ... not (null) anymore

    UIButton *theButton = (UIButton *)[theHeaderView viewWithTag:101];
    [theButton setTitle:@"+" forState:UIControlStateNormal];
}

---

Second Approach:

Using a custom UITableViewHeaderFooterView subclass:

1. Created a UITableViewHeaderFooterView subclass and named it CustomHeaderView
2. Created a View interface nib file for the class
3. In the xib, selected the View & in it's Identity Inspector
   • Specified the Custom Class as CustomHeaderView
4. Made properties, synthesized and connected them in the xib
   • @property (strong, nonatomic) IBOutlet UILabel *lblSomething;
   • @property (strong, nonatomic) IBOutlet UIButton *btnSomething;

Modified the -viewForHeaderInSection: & -didSelectRowAtIndexPath: as:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    static NSString *HeaderIdentifier = @"header";

    CustomHeaderView *myHeader = [tableView dequeueReusableHeaderFooterViewWithIdentifier:HeaderIdentifier];
    if(!myHeader) {
    //    [tableView registerClass:[CustomHeaderView class] forHeaderFooterViewReuseIdentifier:HeaderIdentifier];
        myHeader = [[[NSBundle mainBundle] loadNibNamed:@"CustomHeaderView"
                                                  owner:self
                                                options:nil] objectAtIndex:0];
    }

    [myHeader.btnSomething setTitle:@"-" forState:UIControlStateNormal];
    [myHeader.lblSomething setText:[NSString stringWithFormat:@"Section: %d",section]];

    return myHeader;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    CustomHeaderView *theHeaderView = (CustomHeaderView*)[tableView headerViewForSection:indexPath.section];
    NSLog(@"%@",theHeaderView);

    [theHeaderView.lblSomething setAlpha:theHeaderView.lblSomething.alpha-0.1];
    [theHeaderView.btnSomething setTitle:@"+" forState:UIControlStateNormal];
}

---

PS: The issue with UITableViewHeaderFooterView is that it is iOS6+ only and if, for any reason, your header is/must be a UIView, then see the next method

---

METHOD 2:

Using a simple UIView:

-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    UIView *vwHeader = [[UIView alloc] init];
    [vwHeader setTag:200 + section]; //[1] first method

    switch (section) {
        case 0:
            [vwHeader setBackgroundColor:[UIColor greenColor]];
            break;
        case 1:
            [vwHeader setBackgroundColor:[UIColor redColor]];
            break;
        default:
            break;
    }

    UILabel *lblTitle = [[UILabel alloc] init];
    [lblTitle setFrame:CGRectMake(10, 0, 100, 30)];
    [lblTitle setTag:100 + section]; //[2] alternative method
    [lblTitle setBackgroundColor:[UIColor clearColor]];
    [lblTitle setText:[NSString stringWithFormat:@"Section: %d",section]];

    [vwHeader addSubview:lblTitle];
    return vwHeader;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UIView *vwTest = [self.tableView viewWithTag:200 + indexPath.section]; //[1]
    NSLog(@"[1] : %@",vwTest);

    //or

    UILabel *lblTest = (UILabel *)[self.tableView viewWithTag:100 + indexPath.section]; //[2]
    NSLog(@"%@",lblTest.text);
    UIView *vwTestForSuperview = lblTest.superview;
    NSLog(@"[2] : %@",vwTestForSuperview);
}

---

PS: I know this code doesn't serve any great purpose but this is just an example for others.

Answer 2

I think your problem can be solved easily enough:

-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{    
UITableViewHeaderFooterView *myHeader = [[UITableViewHeaderFooterView alloc] init];
switch (section) {
    case 0:
        [myHeader setBackgroundColor:[UIColor greenColor]];
        break;
    case 1:
        [myHeader setBackgroundColor:[UIColor redColor]];
        break;
    default:
        break;
}

UILabel *myLabel = [[UILabel alloc] init];
[myLabel setFrame:CGRectMake(10, 0, 100, 30)];
[myLabel setTag:101];
[myLabel setBackgroundColor:[UIColor clearColor]];
[myLabel setText:[NSString stringWithFormat:@"Section: %d",section]];

[myHeader addSubview:myLabel];    
return myHeader;

}

Basically, you need to use UITableViewHeaderFooterView class to return from viewForHeaderInSection callback. After that, calling headerViewForSection on your table view will be returning you valid instances of objects instead of nil.