How can I update/reload/refresh a section header view in a UITableView?

Question

I\'m willing to change a specific header view of my UITableView when I click a row.

I\'ve read all posts about it yet. I tried \"reloadData\", \"setNeed

Answer 1

Have you tried reloadRowsAtIndexPaths:withRowAnimation: where you set the row property of the NSIndexPath passed in as NSNotFound? So reloading just the header of section 3, for instance would look like

NSIndexPath * headerIndexPath = [NSIndexPath indexPathForRow: NSNotFound section:3];
[self.tableView reloadRowsAtIndexPaths:@[headerIndexPath] withRowAnimation: UITableViewRowAnimationAutomatic];

I guarantee nothing, but I'm pretty sure it used to work before, because I used it a couple of times.

But even if it works, it's still a hack that might get broken by Apple any time.

edit

Ok, never mind. I tried this with iOS 7 in Xcode 5 and for some reason, even with NSNotFound as the row number, it still reloads the whole sections (with all its cells). So this does not work any more, damn.

Answer 2

You just change it directly. I created an instance variable in the header file for a label that I will put in the header's view I'll create:

@interface MainViewController : UITableViewController {
    // creating my datasource array instance variable
    NSArray *_items;

    // this is the label I will add to the header view when I create it
    UILabel *_headerLabel;
}

@end

And in my tableView when they select a row I call a function that simply changes the text on the label:

@implementation MainViewController

- (id)init {
    self = [super initWithStyle:UITableViewStyleGrouped];

    / filling my datasource with test strings
    _items = @[@"one", @"two"];

    return self;
}

- (void)changeHeaderLabel:(NSString *)newLabel {
    // when this function gets called and is passed a string, I will simply
    // set the text on the label to the new string and viola!
    _headerLabel.text = newLabel;
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // this table will only have a single section for demo purposes
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // return the count of my datasource array
    return _items.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    // attempt to create a cell by reusing one with a given identifier
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];

    // if I wasn't able to reuse one
    if (cell == nil) {
        // create one from scratch with that identifier
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"];
    }

    // now simply set the text on the cell from my data source array of strings
    cell.textLabel.text = _items[indexPath.row];

    // and return the cell
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // deselect the row so the cell automatically fades out after selection
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

    // here you could do one of two things, either get a reference to the cell itself,
    // and then get the value stored in it's textLabel
    UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
    NSString *newHeaderTitleString = selectedCell.textLabel.text;

    // OR you can get it right from your datasource
    NSString *newHeaderTitleString = _items[indexPath.row];

    // then just call the above function with the string as the single param
    [self changeHeaderLabel:newHeaderTitleString];
}

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    // here I just create a view that will span the whole frame and is an arbitrary height
    UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, 80)];
    // set the background color to clear
    headerView.backgroundColor = [UIColor clearColor];

    // then I initialize my instance variable with a frame that's centered in the view
    // for aesthetic purposes
    _headerLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 0, self.view.frame.size.width - 10, 80)];

    // then I set the text color, add an autoresizing mask so if the view rotates
    // it still remains centered properly, set the text to some starting value, 
    // and add it to the headerView I previously created
    _headerLabel.textColor = [UIColor darkGrayColor];
    _headerLabel.autoresizingMask = UIViewAutoresizingFlexibleWidth;
    _headerLabel.text = @"Before";
    [headerView addSubview:_headerLabel];

    // then I return the headerView
    return headerView;
}

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
    // return an arbitrary height here for testing
    return 80;
}

That results in the following:

If you have any questions let me know! This is just a quick example to demonstrate it, but you may want to customize the view in a different way altogether. This should at least solve your problem and give you a starting point to work from.