Add child view controller to UINavigationController

Question

I'm trying to add a child view controller to a UIViewController contained in a UINavigationController with this code:

- (void)buttonTapped:(id)sender
{
    MyChildController *viewController = [self.storyboard instantiateViewControllerWithIdentifier:@"MyChild"];
    [self addChildViewController:viewController];
    [self.view addSubview:viewController.view];
    [viewController didMoveToParentViewController:self];


    viewController.view.alpha = 0.0f;
    [UIView animateWithDuration:0.4 animations:^{
        viewController.view.alpha = 1.0f;
    }];
}

But this is the result:

As you can see the UINavigatioBar and the UIToolbar are still on top of the child view controller. How can I put the child view controller on top of all? I've already tried to replace the code with:

[self.navigationController addChildViewController:viewController];
    [self.navigationController.view addSubview:viewController.view];
    [viewController didMoveToParentViewController:self.navigationController];

But in this way the viewDidAppear:animated of the viewController doesn't get called. I don't know, why.

Answer 1

@Sam's comment is correct. You need to call beginApperanceTransition:animated: and endAppearanceTransition for viewDidAppear to be triggered. The reason why UINavigationController does not call viewDidAppear when you add a child view controller is because it has overridden its container composition methods to prevent the programmer from adding a child view controller in strange places. In your case, it doesn't want your child view to cover up the navigation bar. The correct usage of a navigation controller is to have children appear under the navigation bar. Nonetheless, you can still force upon this non-standard UI by manually telling the child when it is appearing and when it has finished appearing.

Add a child to UINavigationController

MyChildViewController* child = [[MyChildViewController alloc] init];
[self.navigationController addChildViewController:child];
child.view.frame = self.navigationController.view.bounds;
[self.navigationController.view addSubview:child.view];
child.view.alpha = 0.0;
[child beginAppearanceTransition:YES animated:YES];
[UIView
    animateWithDuration:0.3
    delay:0.0
    options:UIViewAnimationOptionCurveEaseOut
    animations:^(void){
        child.view.alpha = 1.0;
    }
    completion:^(BOOL finished) {
        [child endAppearanceTransition];
        [child didMoveToParentViewController:self.navigationController];
    }
];

Remove a child from UINavigationController

[child willMoveToParentViewController:nil];
[child beginAppearanceTransition:NO animated:YES];
[UIView
    animateWithDuration:0.3
    delay:0.0
     options:UIViewAnimationOptionCurveEaseOut
    animations:^(void){
        child.view.alpha = 0.0;
    }
    completion:^(BOOL finished) {
        [child endAppearanceTransition];
        [child.view removeFromSuperview];
        [child removeFromParentViewController];
    }
];