UITableView reloadSections/reloadData: header view becomes blank - ios

Question

I have a UITableView with some sections, each has its own header view.
When user taps on the header view of a section, all rows of that section will collapse. What i do is, I set the number of row of that section to 0, and then call :
[self.tableView reloadSections:sections withRowAnimation:UITableViewRowAnimationBottom];
Everything works as expected, except one thing : the header view of the section becomes white blank. When i scroll the table, then the header becomes normal again.
So i guess there's some problem with the drawing of the table.
One funny thing is, if i use UITableViewRowAnimationFade instead, then even when i scroll the table, the header is still white blank.
When I update just ONE section there is also no problem - when I update more than one section the problem occurs.
If i use
[self.tableView reloadData]
instead, then everything works fine.
The reason i use
[self.tableView reloadSections:sections withRowAnimation:UITableViewRowAnimationBottom];
is because i want animation.
Wrapping with beginUpdates / endupdates does not work.

Answer 1

I realize that it's a LONG time since this question was posed but I think all of the answers given below are incorrect.
I had the same problem (with someone else's code) and was about to be fooled by this post when I realized that the code was not doing it's reuse of the table header correctly. The header disappearing was because the code was only supplying a UIView, not a UITableViewHeaderFooterView, registered correctly and set up for reuse.
Have a look at the answer here:
How to use UITableViewHeaderFooterView?
My blank headers went away when I set up a reusable header.

Answer 2

In Swift:
You need to create a class that's a subclass of UITableViewHeaderFooterView and register it to the table view. Then in viewForHeaderInSection, you do let header = tableView.dequeueReusableHeaderFooterView(withIdentifier: "HeaderView") as! YourHeaderView, similar to what you do for UITableViewCells. Then return that header.
The deceptive thing is the function calls for a return of UIView? when it really needs a dequeuedReusableHeaderFooterView or reloadData will cause it to disappear

Answer 3

I found a work-around - not very elegant, but it works.
Instead of providing a NSIndexSet with more than one section, I call the reloadSections within a for-loop with only one section in each call.
looks like:
for (Element *eleSection in self.gruppenKoepfe) {
if ( eleSection.type.integerValue == qmObjectTypeFormularSpalte || eleSection.type.integerValue == qmObjectTypeFormularZeile ) {
[self.tableView reloadSections:[NSIndexSet indexSetWithIndex:nCount] withRowAnimation:UITableViewRowAnimationFade];
}
nCount ++;
}

Answer 4

I was having a similar problem, except I was trying to delete/insert sections, and I found that keeping a strong property pointing to the entire header view (i.e. not just a subview) stopped it disappearing during section updates.
e.g. Property and instantiation
#property (nonatomic, strong) UIView *headerView;
-(UIView *)headerView {
if ( !_headerView ) {
_headerView = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.view.bounds.size.width, 300)];
// add additional view setup, including subviews
}
return _headerView;
}
And in tableView:(UITableView *)viewForHeaderInSection:(NSInteger)section:
-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
if ( section == theCorrectSection ) {
return self.headerView;
}
return nil;
}

Answer 5

I had the same issue and it was none of the above. My problem was that i was hidding the first header and for some reason after more then 10 reloads the header at index 2 was set hidden. When i set headerView.hidden = false it was ok.