Problems with UINavigationController inside of UITabBarController, viewWillAppear not called

Question

As an overview, I'm having issues with a UINavigationController inside of a UITabBarController calling viewWillAppear whenever a view is popped from the stack.

From the delegate, a UITabBarController is made programmatically:

// Create views for Tab Bar
    UINavigationController *view1   = [[UINavigationController alloc] initWithRootViewController:[[newsFeedNavigationController alloc] initWithStyle:UITableViewStylePlain]];
    resizedTabBatItem *tabBarItem1 = [[resizedTabBatItem alloc] initWithTitle:nil image:[UIImage imageNamed:@"newspaper.png"] tag:0];
    [view1 setTabBarItem:tabBarItem1];
    [tabBarItem1 release];

    UIViewController *view2   = [UIViewController new];
    resizedTabBatItem *tabBarItem2 = [[resizedTabBatItem alloc] initWithTitle:nil image:[UIImage imageNamed:@"speechbubble.png"] tag:1];
    [view2 setTabBarItem:tabBarItem2];
    [tabBarItem2 release];

....

// Create the tab bar controller
    bookTabBarController = [BookTabBarController new];
    [[bookTabBarController view] setFrame:CGRectMake(0, 0, 320, 460)];

    // Add the views to it
    NSArray *viewControllers = [NSArray arrayWithObjects:view1, view2, view3, view4, view5, nil];

    [[bookTabBarController tabBarController] setViewControllers:viewControllers];

My newsFeedNavigationController is just a subclassed UITableViewController (and the subclass is not interfering with viewWillAppear, as it's never called in newsFeedNavigationController). In it, items that when clicked will push a new UIViewController into the stack.

The problem is that whenever views are popped off the stack, viewWillAppear is never called in newsFeedNavigationController, and the items in the list remain highlighted. I've been messing with this for a few hours am at the point where I need some help to find out what I am doing wrong.

In my newsFeedNavigationController, I tried to add an NSLog to see if it is called or I did something, but it is never even called.

- (void)viewWillAppear:(BOOL)animated {
    NSLog(@"is viewWillAppear called?");
    [super viewWillAppear:animated];
}

Edit:

Okay, now here is something weird I noticed:

If I run:

[self presentModalViewController:(any UIview) animated:YES];

and then dismiss it, viewWillAppear begins to work properly when popping and pushing views... So now I am stumped. It's not really a solution but maybe an inside of something that is going on.

Answer 1

To answer my own question, I found out what the problem was.

In order to abide by Apple's "No UITabBarController inside of a UINavigationController" I wrote my own tab bar controller (bookTabBarController) which is based off of a standard View Controller. My problem was that the class wasn't passing viewDidAppear down to the class that managed the view controllers, so it never knew it was being shown or not.

Answer 2

Another solution is to set the navigation controller's delegate. Within the delegate, implement the following method:

- (void)navigationController:(UINavigationController *)navigationController  willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    [viewController viewWillAppear:animated];
}

This will ensure that viewWillAppear will get called on any view controller whose view is about to appear in the navigation controller. If you do it this way, viewWillAppear gets called regardless of whether the view is appearing because it is being pushed, or it is appearing because a subview is being popped.

Answer 3

A solution to this problem is to have the UIViewController containing the UINavigationController pass the desired messages to it. The UINavigationController will forward the messages to the appropriate view controller. It seems counterintuitive but it works.

@interface NavigationWrapperViewController : UIViewController {
    // navigationController must be a subview of this view controller's view
    UINavigationController *navigationController;
}
@property (nonatomic, assign) UINavigationController *navigationController;
@end

@implementation NavigationWrapperViewController
@synthesize navigationController;

-(void)viewWillAppear:(BOOL)animated {
    [navigationController viewWillAppear:animated];
}
-(void)viewDidAppear:(BOOL)animated {
    [navigationController viewDidAppear:animated];
}
-(void)viewWillDisappear:(BOOL)animated {
    [navigationController viewWillDisappear:animated];
}
-(void)viewDidDisappear:(BOOL)animated {
    [navigationController viewDidDisappear:animated];
}

@end

You can find a more complete solution on Pastebin (which I did not post).

Thanks to davidbenini.it and jaekwon for this solution.

Answer 4

An even simpler trick:

In your subclass of UITabBarController, override this:

-(void)loadView{

    [super loadView];

    //here goes the trick:
    [self setSelectedIndex:1];
    [self setSelectedIndex:0];
}

Answer 5

OK, this is old, very old, but I ended up here with a similar problem.

  UITabViewController
     UINavigationController
       UITableViewController1
         UITableViewController2

When popping out of the UITableViewController2, the viewWillAppear function in UITableViewController1 was never called.

The problem: My UITabViewController custom class was overriding viewWillAppear without calling the super implementation.