I want to implement TabBarController and add Navigation Controller View but in vain

Iknow how to add a TabBar with two TabBar buttons on it by Interface Builder. And I link each button to a Navigation Controller.

Now I want to learn how to do everything programmatically. Now I can see a TabBar in simulator but with no buttons on it. Can someone please help me with this. Thanks!

Here's the TabBarAppDelegate.h.

#import <UIKit/UIKit.h>
@interface TabBarAppDelegate : NSObject <UIApplicationDelegate> 
{
    UIWindow *window;
    UITabBarController *tabBarController;
    IBOutlet UINavigationController *navigationController1;
    IBOutlet UINavigationController *navigationController2;
}

@property (nonatomic, retain) 开发者_开发知识库IBOutlet UIWindow *window;
@property (nonatomic, retain) UITabBarController *tabBarController;
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController1;
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController2;
@end

Here's TabBarAppDelegate.m.

#import "TabBarAppDelegate.h"
#import "FirstViewController.h"
#import "SecondViewController.h"
@implementation TabBarAppDelegate
@synthesize window=window;
@synthesize tabBarController;
@synthesize navigationController1;
@synthesize navigationController2;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    tabBarController = [[UITabBarController alloc]init];   
    FirstViewController *firstViewController = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
    firstViewController.title = @"First";
    [self.navigationController1 pushViewController:firstViewController animated:NO];

    SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
    secondViewController.title = @"NavCal";
    [self.navigationController2 pushViewController:secondViewController animated:NO];

    tabBarController.viewControllers = [NSArray arrayWithObjects:navigationController1, navigationController2, nil];

    [window addSubview:tabBarController.view];
    [self.window makeKeyAndVisible];
    [firstViewController release];
    [secondViewController release];
    return YES;
}

- (void)dealloc
{
    [tabBarController release];
    [window release];
    [super dealloc];
}

It looks like you are not initializing the navigation view controllers. See if this would work:

TabBarAppDelegate.h

• Remove the properties navigationController1 and navigationController2

TabBarAppDelegate.m

• Replace

  [self.navigationController1 pushViewController:firstViewController animated:NO];
  

with

UINavigationController *navigationController1 = [[UINavigationController alloc] initWithRootViewController:firstViewController];

• Replace

  [self.navigationController2 pushViewController:secondViewController animated:NO];
  

with

UINavigationController *navigationController2 = [[UINavigationController alloc] initWithRootViewController:secondViewController];

• Release navigationController1 and navigationController2 after adding them to the tabBarController