UINavigationController popToRootViewController doesn't reset Title, clear backbutton

Question

I am stuck trying to customize UINavigationController's backbutton. In RootViewController I set self.title in viewDidLoad, and this string appears in Navigation Bar. In -didSelectRowAtIndexPath I create child view controller, configure back button and call -pushViewController. Processing for child will push child viewcontrollers onto the stack; I need back button to pop to initial view, just as when going back from first child view controller. Currenty backbutton will pop to prior view, so if there are 5 child view controllers on the stack, I have to hit back button 5 times to get to root view. I am unable to get action to fire off when back button is displayed. I am able to popToRootViewController when in child VC; however, backbutton now appears on root view(!) and I have to hit backbutton once more to restore original title and remove backbutton. Here is part of root -viewDidLoad:

- (void)viewDidLoad {
    self.title = @"My Nav Bar Title";     // displays on root navigation bar title
    // some setup code...
    [super viewDidLoad];
}

Here is part of -didSelectRowAtIndexPath, where selecting a tableview cell results in child view being pushed onto stack:

- (void)tableView:(UITableView *)tableView 
didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
   ChildVC *child = [[ChildVC alloc]
                             initWithNibName:@"Child"
                             bundle:nil];

    [self.navigationController dismissModalViewControllerAnimated:YES]; 
    [tableView deselectRowAtIndexPath:indexPath animated:YES]; 

    UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"Quiz" style:UIBarButtonItemStylePlain target:self action:@selector(backToMenu)];
    self.navigationItem.backBarButtonItem = backButton;
    [backButton release];

    [self.navigationController pushViewController:child
                                          animated:YES];
     [child release];
}

Here is action method which doesn't fire when backbutton is pressed:

-(void)backToMenu {
    NSLog(@" in root backToMenu");
    [self.navigationController popViewControllerAnimated:YES];
}

ChildVC will also create a new child in its -didSelectRowAtIndexPath and push the new child controller, as the next child 'page':

- (void)tableView:(UITableView *)tableView 
didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    Child *newChild = [[Child alloc]
                             initWithNibName:@"Child"
                             bundle:nil];

    [self.navigationController dismissModalViewControllerAnimated:YES]; 
    [tableView deselectRowAtIndexPath:indexPath animated:YES]; 
    self.title = self.quizString;  // child view correctly displays customized title

    UIBarButtonItem *backButton = [[UIBarButtonItem alloc] 
                                   initWithTitle:@"Quiz" 
                                   style:UIBarButtonItemStylePlain 
                                   target:self 
                                   action:@selector(backToMenu)];
    self.navigationItem.backBarButtonItem = backButton;
    [backButton release];

    [self.navigationController pushViewController:newQuestion
                                         animated:YES];
    [newChild release];
}

In Child -viewWillDisappear I set a global variable so I known when to push new child and when to pop back to root:

-(void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:YES];
    if (startOver) {
          [self backToMenu];
    }
}

Child -backToMenu:
-(void)backToMenu {
    [self.navigationController popToRootViewControllerAnimated:YES];
}

Here is the sequence when back button is pressed in Child:

-- Child -viewWillDisappear is invoked, calls -backToMenu -- -backToMenu calls popToRootViewControllerAnimated: -- Child -viewWillDisappear is invoked again, calls -backToMenu -- root -viewWillAppear is invoked -- control returns to Child -backToMenu

Root view appears correctly, but Nav bar contains back button and title just like it still was a Child view. Pressing back button removes back button an restores original title.

How can I make this work? Ideally I would like to only have 1 child view on the stack, but I can't figure out how; then the back button would go back to root view. But when I tried this, I got NSInvalidArgumentException', reason: 'Pushing the same view controller instance more than once is not supported...'

Also, anything obvious why action is not fired when backbutton is pressed? Any help is GREATLY appreciated...thx

score 0 · Answer 1 · edited Mar 15 '13 at 07:26

UIBarButtonItem *btnBack=[[UIBarButtonItem alloc]initWithTitle:@"" style:UIBarButtonItemStyleDone target:self action:@selector(back:)] ;
    self.navigationItem.leftBarButtonItem=btnBack;
    //Add image on back button
    UIImage *backButtonImage = [[UIImage imageNamed:@"btn_back.png"] resizableImageWithCapInsets:UIEdgeInsetsMake(0, 13, 0, 6)];
    [btnBack setBackgroundImage:backButtonImage forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];

put this code in your view controller[initWithNibName method]form where you want to pop at root view controller

- (void) back : (id)sender
{

 [self.navigationController popToRootViewControllerAnimated:YES];

}

score 0 · Answer 2 · edited Dec 12 '18 at 02:08

uhm, your backButton calls popToRootViewController, which calls viewWillDissapear, which, if startOver is true calls popToRootViewController AGAIN? what happens if it's false anyway? it continues the popToRootViewController called earlier ...

backButton->popToRoot->viewWillDissapear->check startOver
->YES->popToRoot->viewWillDissapear again->check startOver again->??
->NO->continue the disappearing of the view that was called also by popToRoot

isn't that if there redundant, since both it's branches continue previously popToRoot or call popToRoot again?

why not test for startOver first(in your backToMenu), then popToRootViewController if true?

UINavigationController popToRootViewController doesn't reset Title, clear backbutton

2 Answers2