When "programmatically" creating UINavigationController and UITabBarController, how do I address their functions (like viewWillAppear?)

Question

I am creating my Nav and TabBar in code at launch via: IN : myAppDelegate.m

- (void)applicationDidFinishLaunching:(UIApplication *)application { 
    // set up a local nav controller which we will reuse for each view controller
    UINavigationController *localNavigationController;

    // create tab bar controller and array to hold the view controllers
    tabBarController = [[UITabBarController alloc] init];
    NSMutableArray *localControllersArray = [[NSMutableArray alloc] initWithCapacity:4];

    // setup the first view controller (Root view controller)
    RootViewController *myViewController;
    myViewController = [[RootViewController alloc] initWithTabBar];

    // create the nav controller and add the root view controller as its first view
    localNavigationController = [[UINavigationController alloc] initWithRootViewController:myViewController];

    // add the new nav controller (with the root view controller inside it)
    // to the array of controllers
    [localControllersArray addObject:localNavigationController];

    // release since we are done with this for now
    [localNavigationController release];
    [myViewController release];

    // setup the first view controller just like the first 
    ResortsListViewController *resortsListViewController;
    resortsListViewController = [[ResortsListViewController alloc] initWithNibName:@"ResortsListView" bundle:nil];
    resortsListViewController.title = @"Category1";
    resortsListViewController.tabBarItem.image = [UIImage imageNamed:@"image1.png"];
    resortsListViewController.navigationItem.title=@"Category1";
    localNavigationController = [[UINavigationController alloc] initWithRootViewController:resortsListViewController];
    [localControllersArray addObject:localNavigationController]; 
    [localNavigationController release];

    // setup the second view controller just like the first 
    ResortsListViewController *resortsListViewController;
    resortsListViewController = [[ResortsListViewController alloc] initWithNibName:@"ResortsListView" bundle:nil];
    resortsListViewController.title = @"Category2";
    resortsListViewController.tabBarItem.image = [UIImage imageNamed:@"image2.png"];
    resortsListViewController.navigationItem.title=@"Category2";
    localNavigationController = [[UINavigationController alloc] initWithRootViewController:resortsListViewController];
    [localControllersArray addObject:localNavigationController]; 
    [localNavigationController release];

    // setup the third view controller just like the first 
    ResortsListViewController *resortsListViewController;
    resortsListViewController = [[ResortsListViewController alloc] initWithNibName:@"ResortsListView" bundle:nil];
    resortsListViewController.title = @"Category3";
    resortsListViewController.tabBarItem.image = [UIImage imageNamed:@"image3.png"];
    resortsListViewController.navigationItem.title=@"Category3";
    localNavigationController = [[UINavigationController alloc] initWithRootViewController:resortsListViewController];
    [localControllersArray addObject:localNavigationController]; 
    [localNavigationController release];

    [resortsListViewController release];

    // load up our tab bar controller with the view controllers
    tabBarController.viewControllers = localControllersArray;

    // release the array because the tab bar controller now has it
    [localControllersArray release];

    // add the tabBarController as a subview in the window
    [window addSubview:tabBarController.view];

    // need this last line to display the window (and tab bar controller)
    [window makeKeyAndVisible];


}

As you see, I am re-using ResortsListViewController for different category displays (resorts with Beaches, resorts with Pools, resorts with espresso bars) ... now, without harassing me (grin) about the silliness of my categories (cos this is a test app) I need need to do several things:

1. I need to be able to know which tab click caused the ResortsListViewController to be displayed. I was hoping to use TAG but "initWithRootViewController" does not have the "tag" control. So, if i use an imagefilename that is the category name, I can use that filename to distinguish categories...or even navigationItem name. I need to know if there is a way for ResortsListViewController to know which tabbar item click caused it's display. I thought to look for a "action" that I could assign to the tabbar item, but that is not the way tabbarcontroller works.

2. When clicking from one tab to another, the view does indeed change, the title of ResortsListViewController changes, etc...but the TABLEVIEW it holds does not clear and display any new data. Searching the web I have found a possible solution:

http://discussions.apple.com/thread.jspa?threadID=1529769&tstart=0

basically saying:

In order for UINavigationControllers to send "viewWill/Did/Appear/Disappear" messages, it needs to have received "viewWill/Did/Appear/Disappear" from its container.

What is the container for my UINavigationControllers in this situation? myAppDelegate is defined in the .h file as:

NSObject <UIApplicationDelegate, CLLocationManagerDelegate>

and does not have a:

- (void)viewWillAppear:(BOOL)animated {
}

section. When i add one it says "NSObject may not respond to -viewWillAppear" in the debugger.

Been at Objective-C and iPhone developement for a bit over a week...but this confuses me.

any help out there?

thx

J

Answer 1

1) This is fairly simple. You need to set the delegate property for the UITabBarController. You would set this to the controller object that owns your tabbarcontroller (or your app delegate if that is your setup). Whichever object is set as the delegate would then receive:

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController

AND

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController

to manage tab selections. Place one of these methods in the implementation of whatever object you set as the delegate (you would want it to be the object that owns all of the controllers).

2) If you have a UIViewController that appears as a tab selection (such as ResortsListViewController) then you would need to put the viewWillAppear method in the controller implementation yourself:

@implementation ResortsListViewController

- (id)initWithNibName:(NSString *)name bundle:(NSBundle *)bundle {
...
}

... etc. ....

- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[table reloadData];
}

...

@end

Let me know if I misunderstood the second part of your question.

Answer 2

Okay, here goes: This is the correct answer to the question, however, it did not end up being this hard. All I had to do was the following:

Create a property in ResortViewController of type int with variable name whichChoice (for instance). Then address it in the setup of the TabBarController a la:

// setup the first view controller just like the first 
    ResortsListViewController *resortsListViewController;
    resortsListViewController = [[ResortsListViewController alloc]     initWithNibName:@"ResortsListView" bundle:nil];
    //  START HERE IS THE CHANGE
    resortsListViewController.whichChoice = 1;
    //  END HERE IS THE CHANGE
    resortsListViewController.title = @"Category1";
    resortsListViewController.tabBarItem.image = [UIImage imageNamed:@"image1.png"];
    resortsListViewController.navigationItem.title=@"Category1";
    localNavigationController = [[UINavigationController alloc] initWithRootViewController:resortsListViewController];
    [localControllersArray addObject:localNavigationController]; 
    [localNavigationController release];

To find out which tab was clicked when my resortsListViewController takes over, I simply query the class variable: whichChoice to get the answer.

Things like this are so simple you skip over them. I thought you had to pass the variable in an action and specify where it would go with the target like you do in other objects -- but when you set things up ahead of time you do not have to do that. Now, having said that, dynamically setting "whichChoice" is not so easy without a lot more thought...but setting it to a variable KNOWN at setup is fine.

For answer #2, I simply put a variable style of IBOutlet in my class, hooked it up to the table, and then followed your instructions, because without the variable in the IBOutlet and hooking it up to the table, there is no reference to the table view. For some reason hooking up the table simply to the VIEW "Referencing Outlet" and calling [self.tableview reloadData] did not do the job.

But for the most part, your answers were right and led me in the right direction. As an aside, I really hate that you have to right-click and drag from here-to-there in IB if you have an IB element you built. You should be able to hook it up in code using it's ObjectId (or something). That would be more in line with programmers. I know IB is made to allow programming to be easier for designers, but gee wilikers..it is hard to wrap my mind around! I end up dropping IB and creating elements in code most of time time...which I do not know if is as fast to execute. I tend to think not...but have no proof to the contrary.