Implementing my own navigation controller?

Question

I have a tab bar app. Under one of the tabs i want a uisegmentedControl in the top navigation view, that controls what view is currently displayed. This is dead easy if i just exchange the view, but i want to do it in a more organized and generic way, by using one uiviewcontroller for each view and exchanging them in the most optimzed way.

i guess step one would be to know exactly what a tabbar controller sends to a navigation controller/view controller when a tab is changed, and work it out from there.

Can any one point me in the right direction?

Answer 1

Just exchanging the views and keeping up with the current view's viewController is the best way to implement a UISegmentedControl in this regard.

Note: by exchanging the views i mean adding a subview to the current view and removing the old one.

You might be interested in the method below, which is implemented by the UITabBarControllerDelegate

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

Answer 2

Some time ago I stumbled upon SegmentsController which I found in this blog entry from red artisan.
I used it in conjunction with a UITabBarController, but without knowing I did it wrong. Not wrong as in "it crashs" or "it doesn't do what i want" but wrong in the sense that I have to forward each UIViewController call (like viewDidAppear, receivedMemoryWarning etc) to the child viewControllers. The app with the wrong code is still in the app store and I never received a complain about it.

But I played around a while and figured out how to use it right. It's a bit of a hassle but imho it's absolutely worth it. I'll show you the correct version that I have right now, I'm creating the UITabBarController in Interface Builder so I have to change the tab in code. Which introduces another piece of mess, and maybe there is room for improvements. But right now I'm satisfied with this solution.

NSMutableArray *items = [self.tabBarController.viewControllers mutableCopy]; // tabs from tabbar configured in IB

// The two child vc that will appear in the segment control
SomeViewController_iPhone *tvcs = [[[SomeViewController_iPhone alloc] initWithNibName:@"SomeView_iPhone" bundle:nil] autorelease];
SomeOtherViewController_iPhone *tvct = [[[SomeOtherViewController_iPhone alloc] initWithNibName:@"SomeOtherView_iPhone" bundle:nil] autorelease];
NSArray *viewControllers1 = [NSArray arrayWithObjects:tvcs, tvct, nil];

// the nav controller acts as a wrapper around the child viewcontrollers
UINavigationController *navController1 = [[[UINavigationController alloc] init] autorelease];
navController1.tabBarItem.title = NSLocalizedString(@"FirstTab", nil);
navController1.tabBarItem.image = [UIImage imageNamed:@"tabImage1.png"];
navController1.navigationBar.tintColor = [UIColor navBarTintColor];

firstTabSegmentsController = [[SegmentsController alloc] initWithNavigationController:navController1 viewControllers:viewControllers1];

// uses a NSArray category that basically creates a NSArray that has the title properties of the vc in viewControllers1
firstTabSegmentedController = [[UISegmentedControl alloc] initWithItems:[viewControllers1 arrayByPerformingSelector:@selector(title)]];
firstTabSegmentedController.frame = CGRectMake(0, 0, 222, 30);
firstTabSegmentedController.segmentedControlStyle = UISegmentedControlStyleBar;
firstTabSegmentedController.selectedSegmentIndex = 0;

[firstTabSegmentsController indexDidChangeForSegmentedControl:firstTabSegmentedController];

[firstTabSegmentedController addTarget:firstTabSegmentsController action:@selector(indexDidChangeForSegmentedControl:) forControlEvents:UIControlEventValueChanged];

// replace first tab from interface builder with this
[items replaceObjectAtIndex:0 withObject:navController1];

as you see it needs a bit of setup, but in my opinion this solution is better than anything else I've tried throughout the time. I hope I de-NDAed the code correctly.

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Edit: Uploaded a sample project: BeautifulColors.zip