Refresh only the custom header views in a UITableView? - ios

Question

My UITableView has custom UIView headers in every section. I am needing to refresh only the headers and not the other content in the section. I have tried out [self.tableView headerViewForSection:i] and it does not return anything even though it should. Is there anyway that I can do this?
Edit: Code based around new suggestion
I have given this a shot as well and it calls/updates the UIView within that method, but the changes do not visually propagate onto the screen.
for (int i = 0; i < self.objects.count; i++) {
UIView *headerView = [self tableView:self.tableView viewForHeaderInSection:i];
[headerView setNeedsDisplay];
}

Answer 1

Instead of calling setNeedsDisplay, configure the header yourself by setting it's properties. And of course you have to get the actual headers in the table, don't call the delegate method, because that method usually creates a new header view.
I usually do this in a little helper method that is called from tableView:viewForHeaderInSection: as well.
e.g.:
- (void)configureHeader:(UITableViewHeaderFooterView *)header forSection:(NSInteger)section {
// configure your header
header.textLabel.text = ...
}
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
UITableViewHeaderFooterView *header = [tableView dequeueReusableHeaderFooterViewWithIdentifier:#"Header"];
[self configureHeader:header forSection:section];
}
- (void)reloadHeaders {
for (NSInteger i = 0; i < [self numberOfSectionsInTableView:self.tableView]; i++) {
UITableViewHeaderFooterView *header = [self.tableView headerViewForSection:i];
[self configureHeader:header forSection:i];
}
}

Answer 2

Create your own subclass of UIView for the headerView, and add a couple of methods to it so your view controller can send whatever UI updates you want to it.

Answer 3

Calling setNeedsDisplay only serves to trigger the drawRect: method of the receiving view. Unless this is where your text color logic is (that is, in the drawRect method of your UIView subclass that you are using for header views), nothing is likely to change. What you need to do is directly call something on the header views to update their state based on your new or changed data or directly access the label in the header view and change it yourself while iterating through them. setNeedsDisplay will only trigger code found in the drawRect: method of the view.

Answer 4

I recently had this exact problem and only overcame it by keeping a pointer to the headers as they were created. I did it in Swift and with a swift only dictionary type but the idea could be massaged into objC somehow.
var headers : [ Int : UIView ] = [ : ] //dictionary for keeping pointer to headers
override func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
if let h = super.tableView(tableView , viewForHeaderInSection: section) { //or create your view (this viewController inherits it)..
self.headers.updateValue(h , forKey: section) //keep a pointer to it before you return it..
return h
}
return nil
}

Answer 5

When you create your custom header views, use UITableViewHeaderFooterView instead of a simple UIView and when you initialize it, use something like this:
UITableViewHeaderFooterView *cell = [[UITableViewHeaderFooterView alloc] initWithReuseIdentifier:#"reuseIdentifier"];
The reuseIdentifier will tell your UITableView to keep track of the header and it should no longer return null when you try to access it with [self.tableView headerViewForSection:i]
You should then be able to use setNeedsDisplay on the UITableViewHeaderFooterView you get back from headerViewForSection after making your modifications.

Answer 6

Swift 5 Solution:
Delegate method of your table view:
override func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
// Ideally, dequeue your header view...
var view: UITableViewHeaderFooterView?
if section == 0 { view = ... // dequeue appropriately
} else if section == 1 { view = ... // dequeue appropriately
} else ... // etc.
setupHeaderView(&view)
return view
}
In the area of code where you want to do the header view update:
var headerView = tableView.headerView(forSection: i)
setupHeaderView(&headerView)
Header setup method:
func setupHeaderView(_ view: inout UITableViewHeaderFooterView?) {
// do something with `view` here
}

Answer 7

tableView.reloadSections([0,0], with: .automatic)
https://developer.apple.com/documentation/uikit/uitableview/1614954-reloadsections

Answer 8

Swift 5 :
If you are using custom view as a table header view then try below code
-- Make your custom class as a subclass of UITableViewHeaderFooterView.
class MyCustomHeaderView : UITableViewHeaderFooterView {
#IBOutlet weak var sampleLabel: UILabel!
}
-- Then fetch your view using below method (using section number)
func updateHeaderView() {
// This is for section no. 1, you can use `for loop` for all sections
if let headerView = self.myTableView.headerView(forSection: 1) as? MyCustomHeaderView {
// Set values or update constraints to your view
headerView.sampleLabel.text = "your new text goes here"
headerView.sizeToFit() //Resizes and moves the receiver view so it just encloses its subviews
self.myTableView.beginUpdates()
self.myTableView.endUpdates()
// if you are using for loop then keep this `beginUpdates` and `endUpdates` outside loop
}
}