You have to change tabbar selectedIndex like,
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
if([userInfo valueForKey:@"app"]) {
NSString *action_app = [userInfo valueForKey:@"app"];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:action_app forKey:@"app"];
UITabBarController *tabb = (UITabBarController *)self.window.rootViewController;
tabb.selectedIndex = 2;
}
}