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

Question

I am having problems finding any other information than the docs for how to save the tab order for my UITabBarController, so that the user's customization is saved for next app launch. I have searched online, but have been unable to find any blog posts or articles that goes through the proper code for doing this.

I realize I have to use the delegate methods for the UITabBarController (didEndCustomizingViewControllers:) but I am not sure how I best approach persistance in terms of saving the state of the order the user wants the tabs in.

Can someone post some code, point me in the right direction or perhaps you have a link for something saved? :)

Thanks

Answer 1

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.