如何在iOS 5中访问标签栏控制器？

Question

In Xcode 4.2, I created a new project from the "tabbed application" template. Now I want to access the tab bar controller in the AppDelegate, but this property is missing. How to solve the problem.

In previous version of Xcode, I can access it by calling the self.tabBarController, however, I could not do that in iOS 5.

Answer 1

There's no magic happening with the tabBarController property that appears in "tabbed application" template projects. I guess pre-iOS 5 the template was designed so that the tab controller was already set up as an attached outlet for you. If it's not in the template you're using then you just need to add the property yourself. Below are instructions on how to do this.

You just need to add a property for it and then grab the rootViewController from your UIWindow in applicationDidFinishLaunching . ie you want something like this in your app delegate header:

@interface MyAppDelegate : NSObject <UIApplicationDelegate>
...
@property (nonatomic, strong) UITabBarController *tabBarController;
...
@end

Then synthesise it in your app delegate implementation and grab it from rootViewController :

@implementation MyAppDelegate

@synthesize tabBarController;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.tabBarController = (UITabBarController*)self.window.rootViewController;
    return YES;
}

@end

Answer 2

if u're using 4.2, i'm pretty sure that on the appDelegate, its automatically added

@property (strong, nonatomic) UITabBarController *tabBarController;

u can access it on the implementation file by using the method u've been using, self.tabBarController

just make sure that it's properly synthesized on the implementation file and u write the code in the proper method body

im sorry but im not very clear of what your problem is