Calling a UITableViewDelegate method from ViewController

I'd like to call the following method from my view controller class:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section; 

However for the life of me I can't figure out how to do it. I tried:

UIView *view = [tableView viewForHeaderInSection:section];
UIView *view = [self viewForHeaderInSection:section];
UIView *view = [self tableView:viewForHeaderInSection:section];

All give me errors. It's that extra tableView: bit on the beginning. Can anyone give some advic开发者_Go百科e or at least explain what that tableView:(UITableView *)tableView means?

Thanks! Steve

I don't know why you would want to call it, but if it is implemented in the same object that you're calling it from then you can use self:

UIView* view = [self tableView:tableView viewForHeaderInSection:section];

otherwise, you can get the delegate from the tableView and call the delegate:

id<UITableViewDelegate> theDelegate = tableView.delegate;
UIView* view = [theDelegate tableView:tableView viewForHeaderInSection:section];

Why would you want to call it? This is one of the UITableViewDelegate methods that are normally called automatically when the table is being constructed by the tableView. The tableView class object fills in the parameters that it needs when it makes the call to this method. The view controller only needs to provide the right delegate methods, customized by you, so it can set it up properly.

Did you customize the code, as in this example, in your delegate class?

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    // create the parent view that will hold header Label
    UIView* customView = [[UIView alloc] initWithFrame:CGRectMake(10.0, 0.0, 300.0, 44.0)];

    // create the button object
    UILabel * headerLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    headerLabel.backgroundColor = [UIColor clearColor];
    headerLabel.opaque = NO;
    headerLabel.textColor = [UIColor blackColor];
    headerLabel.highlightedTextColor = [UIColor whiteColor];
    headerLabel.font = [UIFont boldSystemFontOfSize:20];
    headerLabel.frame = CGRectMake(10.0, 0.0, 300.0, 44.0);

    // If you want to align the header text as centered
    // headerLabel.frame = CGRectMake(150.0, 0.0, 300.0, 44.0);

    headerLabel.text = <Put here whatever you want to display> // i.e. array element
    [customView addSubview:headerLabel];

    return customView;
}

I'm not near my Mac, or I would give you one of my own examples. But this is the general way this method is used.

By the way, you can see that the parameter tableView is not referenced in the sample code above. If you really want to call this method, use nil. UITableViewDelegate protocol allows the controller to be delegate for more than one tableView. If this happens, the method should test to see which tableView is reference, so that specialized behavior can be accommodated for each tableView.

Additional info:

If you just want to see what the height of your tableView's header is, you can evaluate its sectionHeaderHeight property. There are other properties like this, such as sectionFooterHeight and rowHeight.

You should know that delegate methods are there to help the tableView, using your customization. So the delegate method tableView:heightForHeaderInSection: is actually for you to customize the header height. Your delegate methods tells the tableView what the height is. It isn't a way to examine a property of the tableView.

Apples documentation says that if you customize by using tableView:heightForHeaderInSection: then the tableView sectionHeaderHeight is not valid. You would expect this, because that property refers to the height of all of the section headers.

Using the sectionHeaderHeight property, which you can write to in this case, you can set all of the headers to the same height.

Here is some sample code from something I'm working on now. I've added an NSLog statement for you.

resultsTableVC = [[[ResultsTableVC alloc] initWithController:self] retain];

self.tableView = [[[UITableView alloc] initWithFrame:CGRectMake(0, 110, self.view.frame.size.width, self.view.frame.size.height-120) style:UITableViewStyleGrouped] retain];
self.tableView.autoresizingMask = UIViewAutoresizingFlexibleHeight;
self.tableView.autoresizesSubviews = YES;
self.tableView.layer.cornerRadius = 10.0f;

self.tableView.delegate = resultsTableVC;
self.tableView.dataSource = resultsTableVC;
self.tableView.backgroundView = nil;
self.tableView.backgroundColor = [UIColor clearColor];
self.tableView.separatorColor = [UIColor defaultResultTableBackgroundColor];
self.tableView.separatorStyle = UITableViewCellSeparatorStyleSingleLine;

[self.view addSubview:self.tableView];

NSLog(@"header: %f, row: %f", tableView.sectionHeaderHeight, tableView.rowHeight);

(Someone will probably point out that I don't need some of those retains. I'm still working on that.)

This tells me that the standard section height is 100 and the standard row height is 44.0. I have a pointer to my tableView, a property that I can use through this class.

Now if you are setting the header height using tableView:heightForHeaderInSection: then you should have the height already calculated in your program. I don't think you can query for the height of a particular section (or row) once you set it.

Does this help?