When to call addChildViewController

Question

I'm trying to have something similar to a UINavigationController so I can customize the animations. To start, I'm just using Apple stock animations. Here's my containerViewController:

- (void)loadView {
    // Set up content view
    CGRect frame = [[UIScreen mainScreen] bounds];
    _containerView = [[UIView alloc] initWithFrame:frame];
    _containerView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    self.view = _containerView;

}

- (id)initWithInitialViewController:(UIViewController *)vc {
    self = [super init];
    if (self) {
        _currentViewController = vc;

        [self addChildViewController:_currentViewController];
        [self.view addSubview:_currentViewController.view];
        [self didMoveToParentViewController:self];

        _subViewControllers = [[NSMutableArray alloc] initWithObjects:_currentViewController, nil];
    }
    return self;
}



- (void)pushChildViewController:(UIViewController *)vc animation:(UIViewAnimationOptions)animation {
    vc.view.frame = _containerView.frame;
    [self addChildViewController:vc];

    [self transitionFromViewController:_currentViewController toViewController:vc duration:0.3 options:animation animations:^{

    }completion:^(BOOL finished) {
        [self.view addSubview:vc.view];
        [vc didMoveToParentViewController:self];
        [self.subViewControllers addObject:vc];
    }];
}

- (void)popChildViewController:(UIViewController *)vc WithAnimation:(UIViewAnimationOptions)animation {
    // Check that there is a view controller to pop to
    if ([self.subViewControllers count] <= 0) {
        return;
    }

    NSInteger idx = [self.subViewControllers count] - 1;
    UIViewController *toViewController = [_subViewControllers objectAtIndex:idx];
    [vc willMoveToParentViewController:nil];

    [self transitionFromViewController:vc toViewController:toViewController duration:0.3 options:animation animations:^{

    }completion:^(BOOL finished) {
        [vc.view removeFromSuperview];
        [vc removeFromParentViewController];
        [self didMoveToParentViewController:toViewController];
        [self.subViewControllers removeObjectAtIndex:idx];
    }];
}

I have this ContainerViewcontroller as my rootViewController of the window. I can add my initial viewController and push a view controller. When I try to pop though, I get

ContainerViewController[65240:c07] Unbalanced calls to begin/end appearance transitions for <SecondViewController: 0x8072130>.

I'm wondering what I am doing wrong. I figured my initialViewController is still underneath the secondViewController. Any thoughts? Thanks!

Answer 1

I don't know if this is what's causing your problem, but shouldn't this:

[self didMoveToParentViewController:toViewController];

be:

[toViewController didMoveToParentViewController:self];

Also, I'm not sure what you're doing with the subViewControllers array. It seems to be a duplication of the childViewControllers array that is already a property of a UIViewController.

One other thing I'm not sure is right. In your pop method your toViewController is the last controller in the _subViewControllers array. Don't you want it to be the second to last? Shouldn't the last be the one you're popping? You're popping vc, which is a controller you're passing in to the method, I don't understand that.

This is the way I've made a navigation like controller. In its containment behavior, it acts like a navigation controller, but without a navigation bar, and allows for different transition animations:

@implementation ViewController

-(id)initWithRootViewController:(UIViewController *) rootVC {
    if (self = [super init]) {
        [self addChildViewController:rootVC];
        rootVC.view.frame = self.view.bounds;
        [self.view addSubview:rootVC.view];
    }
    return self;
}


-(void)pushViewController:(UIViewController *) vc animation:(UIViewAnimationOptions)animation {
    vc.view.frame = self.view.bounds;
    [self addChildViewController:vc];
    [self transitionFromViewController:self.childViewControllers[self.childViewControllers.count -2] toViewController:vc duration:1 options:animation animations:nil
            completion:^(BOOL finished) {
            [vc didMoveToParentViewController:self];
            NSLog(@"%@",self.childViewControllers);
    }];
}

-(void)popViewControllerAnimation:(UIViewAnimationOptions)animation {
    [self transitionFromViewController:self.childViewControllers.lastObject toViewController:self.childViewControllers[self.childViewControllers.count -2] duration:1 options:animation animations:nil
                            completion:^(BOOL finished) {
                                [self.childViewControllers.lastObject removeFromParentViewController];
                                NSLog(@"%@",self.childViewControllers);
                            }];
}

-(void)popToRootControllerAnimation:(UIViewAnimationOptions)animation {
    [self transitionFromViewController:self.childViewControllers.lastObject toViewController:self.childViewControllers[0] duration:1 options:animation animations:nil
                            completion:^(BOOL finished) {
                                for (int i = self.childViewControllers.count -1; i>0; i--) {
                                    [self.childViewControllers[i] removeFromParentViewController];
                                }
                                NSLog(@"%@",self.childViewControllers);
                            }];
}

After Edit: I was able to duplicate the back button function with this controller by adding a navigation bar to all my controllers in IB (including in the one that is the custom container controller). I added a bar button to any controllers that will be pushed, and set their titles to nil (I got some glitches if I left the title as "item"). Deleting that title makes the button disappear (in IB) but you can still make connections to it in the scene list. I added an IBOutlet to it, and added this code to get the function I wanted:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    if (self.isMovingToParentViewController) {
        self.backButton.title = [self.parentViewController.childViewControllers[self.parentViewController.childViewControllers.count -2] navigationItem].title;
    }else{
        self.backButton.title = [self.parentViewController.childViewControllers[self.parentViewController.childViewControllers.count -3] title];
    }
}

I've shown two different ways that worked to access a title -- in IB you can set a title for the controller which I used in the else clause, or you can use the navigationItem title as I did in the if part of the clause. The "-3" in the else clause is necessary because at the time viewWillAppear is called, the controller that is being popped is still in the childViewControllers array.