iOS selected tab

问题

I'm trying to determine which tab has been selected by the user. I melded this together from a couple of tutorials on iOS tab bars. In my appDelegate I have this code:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

//We need to implement the view controllers within the tab controller and make the tab controller the root controller of our app - note we are only using view 1-3 at first.

FirstViewController *fistView = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
SecondViewController *secondView = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
ThirdViewController *thirdView = [[ThirdViewController alloc] initWithNibName:@"ThirdViewController" bundle:nil];
FourthViewController *fourthView = [[FourthViewController alloc] initWithNibName:@"FourthViewController" bundle:nil];

NSArray *viewControllersArray = [[NSArray alloc] initWithObjects:fistView, secondView, thirdView, fourthView, nil];

self.tabController = [[UITabBarController alloc] init];
[self.tabController setViewControllers:viewControllersArray animated:YES];

self.window.rootViewController = self.tabController;

//end custom code

self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}

Is viewControllerArray the delegate for my tabController?

When I place this code on the page nothing happens:

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
    if (tabBarController.selectedIndex == 0) {
        NSLog(@"ok");
    }
}

回答1:

You can simply add self.tabController.delegate = self and make sure that your AppDelegate conforms to the UITabBarControllerDelegate protocol.

I also suggest placing a log outside the if in your delegate method, to confirm that it is actually called.

回答2:

In this case, your app delegate should be the delegate for the tabBarController.

来源：https://stackoverflow.com/questions/10608669/ios-selected-tab