Re: [iPhone] (newbie) navigation controller is null, combining navigation controller and tab bar controller
Re: [iPhone] (newbie) navigation controller is null, combining navigation controller and tab bar controller
- Subject: Re: [iPhone] (newbie) navigation controller is null, combining navigation controller and tab bar controller
- From: Greg Titus <email@hidden>
- Date: Mon, 15 Jun 2009 09:17:59 -0700
Hi Beth,
Something that you might try, just to simplify the number of IB
hookups and cut down on the possibility of errors there, is to change
this line:
[delegate.topicsTableNavController pushViewController:questionDetail
animated:YES];
To just:
[self.navigationController pushViewController:questionDetail
animated:YES];
The UIViewController class has a method (-navigationController) to
access the navigation controller that it is currently inside of. Using
it will keep you from having to look up you app delegate, since it
looks like the problem that you are having is that your app delegate's
"topicsTableNavController" outlet is not getting set.
Hope this helps,
- Greg
On Jun 15, 2009, at 8:26 AM, Beth Freeman wrote:
Hello,This is a follow up question to my previous question about
combining a
navigation controller with a tab bar controller.
I have successfully combined the two in building the interface with
Interface Builder: My top level controller is a tab bar controller.
This
references a navigation controller, which references a table view
controller. Selecting a row from the table view is then supposed to
display
a UI view (ie, not another table view). When I run the program, I
see the
tab bar, the navigation bar and the table with my data just fine.
However,
when I select a row from the table, I never see the UI view.
In my accessoryButtonTappedForRowWithIndexPath method (see below) in
my
table view controller, my navigation controller appears to be null.
When I
put a breakpoint at the line when I push the view controller on the
stack,
the address of the navigation controller is 0x0.
I have studied TheElements example from Apple extensively and
believe I am
doing everything correctly in IB. Since TheElements example is built
programmatically, it's a little difficult for me to know if I've done
everything I need to do to hook things up correctly, but I believe I
have.
My understanding is that when I drag a controller from the library
into my
MainWindow.xib window, I'm "instantiating" that as an object. I
have an
object in my MainWindow.xib window whose class is set to
TopicsTableNavController (the navigation controller for the first
tab),
however, as described above, this appears to not be instantiated at
the
breakpoint.
In TheElements example, the navigation controllers are created and
added to
the tab bar view controllers programmatically. My assumption was
that when
you assign the view controllers for the tab bar controller through
IB, and
set the class of each of the view controllers through IB, I'm
instantiating
the objects at that time.
Am I missing something? Is there something I need to do
programmatically to
set up the navigation controller that I don't know about? Am I
wrong about
how IB works?
In the code below, I set up the view controller for the view that
should be
pushed onto the stack (questionDetail) and, I assume, displayed. I
do see
the log message just before the push, and have verified that my view
is
being set up correctly. However, the view is never displayed, I'm
guessing
because the navigation controller is 0x0 and is thus nil.
Thanks so much in advance for any help.
Elisabeth
- (void)tableView:(UITableView *)tableView
accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
if (self.questionDetail == nil) {
QuestionDetail *aQuestionDetail = [[QuestionDetail alloc]
initWithNibName:
@"QuestionDetail" bundle:nil];
self.questionDetail = aQuestionDetail;
[aQuestionDetail release];
}
questionDetail.title = [NSString stringWithFormat:@"Question from %@",
[topicsArray objectAtIndex:row]];
if (QADetail != nil) {
[questionDetail.question setText:[QADetail objectForKey:@"question"]];
[questionDetail.answer setText:[QADetail objectForKey:@"answer"]];
}
NDQAppDelegate *delegate = [[UIApplication sharedApplication]
delegate];
NSLog(@"Pushing Question Detail View Controller");
[delegate.topicsTableNavController pushViewController:questionDetail
animated:YES];
}
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