How to: Save order of tabs when customizing tabs in UITabBarController

iphone, uitabbarcontroller

Solution

As far as you've asked for some sample code I will simply post here how I dealt with the same task in my app.

Quick intro: I was using a NIB file for storing initial `UITabBarController` state and to differ my tabs one from another I simply defined tag variables for `UITabBarItem` objects assigned to each `UIViewController` stuffed in my `UITabBarController`. To be able to accurately track last selected tab (including the 'More' one) I've implemented following methods for `UITabBarControllerDelegate` of my `UITabBarController` and `UINavigationControllerDelegate` of its moreNavigationController. Here they are:

#pragma mark UINavigationControllerDelegate

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    [[NSUserDefaults standardUserDefaults] setInteger:mainTabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    [[NSUserDefaults standardUserDefaults] setInteger:mainTabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

#pragma mark UITabBarControllerDelegate

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
    [[NSUserDefaults standardUserDefaults] setInteger:tabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

And here's the code for saving the tabs order:

#pragma mark UITabBarControllerDelegate

- (void)tabBarController:(UITabBarController *)tabBarController didEndCustomizingViewControllers:(NSArray *)viewControllers changed:(BOOL)changed {
    int count = mainTabBarController.viewControllers.count;
    NSMutableArray *savedTabsOrderArray = [[NSMutableArray alloc] initWithCapacity:count];
    for (int i = 0; i < count; i ++) {
        [savedTabsOrderArray addObject:[NSNumber numberWithInt:[[[mainTabBarController.viewControllers objectAtIndex:i] tabBarItem] tag]]];
    }
    [[NSUserDefaults standardUserDefaults] setObject:[NSArray arrayWithArray:savedTabsOrderArray] forKey:@"tabBarTabsOrder"];
    [savedTabsOrderArray release];
}

As you can see I've been storing the order of tabs' indexes in an array in `NSUserDefaults`.

On app's launch in `applicationDidFinishLaunching:` method I reordered the `UIViewControllers` using following code:

- (void)applicationDidFinishLaunching:(UIApplication *)application {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    mainTabBarController.delegate = self;

    int count = mainTabBarController.viewControllers.count;
    NSArray *savedTabsOrderArray = [[userDefaults arrayForKey:@"tabBarTabsOrder"] retain];
    if (savedTabsOrderArray.count == count) {
        BOOL needsReordering = NO;

        NSMutableDictionary *tabsOrderDictionary = [[NSMutableDictionary alloc] initWithCapacity:count];
        for (int i = 0; i < count; i ++) {
            NSNumber *tag = [[NSNumber alloc] initWithInt:[[[mainTabBarController.viewControllers objectAtIndex:i] tabBarItem] tag]];
            [tabsOrderDictionary setObject:[NSNumber numberWithInt:i] forKey:[tag stringValue]];

        if (!needsReordering && ![(NSNumber *)[savedTabsOrderArray objectAtIndex:i] isEqualToNumber:tag]) {
                needsReordering = YES;
            }
        }

        if (needsReordering) {
            NSMutableArray *tabsViewControllers = [[NSMutableArray alloc] initWithCapacity:count];
            for (int i = 0; i < count; i ++) {
                [tabsViewControllers addObject:[mainTabBarController.viewControllers objectAtIndex:
                                                [(NSNumber *)[tabsOrderDictionary objectForKey:
                                                              [(NSNumber *)[savedTabsOrderArray objectAtIndex:i] stringValue]] intValue]]];
            }
            [tabsOrderDictionary release];

            mainTabBarController.viewControllers = [NSArray arrayWithArray:tabsViewControllers];
            [tabsViewControllers release];
        }
    }
    [savedTabsOrderArray release];

    if ([userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"]) {
        if ([userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"] == 2147483647) {
            mainTabBarController.selectedViewController = mainTabBarController.moreNavigationController;
        }
        else {
            mainTabBarController.selectedIndex = [userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"];
        }
    }

    mainTabBarController.moreNavigationController.delegate = self;

    [window addSubview:mainTabBarController.view];
}

It's quite tricky and may seem strange, but don't forget that my `UITabBarController` was fully created in a nib file. If you construct it programmatically you may simply do the same but following the saved order.

P.S.: and don't forget to synchronize `NSUserDefaults` when your app terminates.

- (void)applicationWillTerminate:(UIApplication *)application {
    [[NSUserDefaults standardUserDefaults] synchronize];
}

I hope this will help. If something is not clear please do comment and ask.

Problem

Original source