How to get UIBarButtonItem to call “pushViewControllerAnimated:(BOOL)” to the UINavigationController?

Question

I'm trying to get a sort of "left to right" hierarchical navigation going, with the UINavigationController. I'm using this code:

-(IBAction)showSettings:(id)sender {
UINavigationController *aNavController = [[UINavigationController alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:aNavController animated:YES];

SecondView *secondView = [[SecondView alloc] initWithNibName:nil bundle:nil];
[aNavController pushViewController:secondView animated:NO];

UIBarButtonItem *aButton = [[UIBarButtonItem alloc] initWithTitle:@"Knapp" style:UIBarButtonItemStylePlain target:self action:@selector(nextView:)];
aNavController.topViewController.navigationItem.rightBarButtonItem = aButton;

[aButton release];
[secondView release];
[aNavController release]; }

-(IBAction)nextView:(id)sender {
ThirdView *thirdView = [[ThirdView alloc] initWithNibName:nil bundle:nil];
[self.navigationController pushViewController:thirdView animated:YES];
NSLog(@"Push it like it's hot"); }

'nextView' is called correctly, the "Push it like it's hot" is printed in "Output", but nothing is pushed, no new view shows up. I've also tried changing: [self.navigationController pushViewController:thirdView animated:YES]; to [self.navigationController popViewControllerAnimated:YES]; but the result stays the same, nothing happens.

My conclusion is this: I'm doing something wrong in the self.navigationController part of 'nextView', i.e the program doesn't know from/to what to push/pop. I've done my best to look at some sort of documentation about this but I can't work it out, so here I am.

Is self.navigationController the right way to do it or am I missing something in that line?

Thank you in advance, Tobias Tovedal

Answer 1

When you are using self.navigationController, you are not accessing the navigation controller defined as aNavController in showSettings. self.navigationController refers to a Navigation that the self view controller may be pushed on. I assume that the view where this code is defined doesn't have a NavigationController. This means self.navigationController is pointing to null. You can verify this in the nextView method by doing NSLog(@"%@", self.navigationController);

What you need to do is make aNavController an Instance Variable in your Header File and then you can do [aNavController pushViewController:thirdView animated:YES]; in your nextView: method.

Answer 2

What appears to be your problem is

UINavigationController *aNavController = [[UINavigationController alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:aNavController animated:YES];

pushes a new model view controller to the stack and does not make this navigation controller the current view controller's navigation controller;

so you need to set the current view controllers navigation controller to aNavController or make aNavController a class variable and use it to push the thirdView.