切换tabbarController，判断是否登录

#import "HomePageViewController.h"

#import "InformationViewController.h"

#import "PublishViewController.h"

#import "FriendsViewController.h"

#import "MyViewController.h"

#import "LoginViewController.h"

@interface BaseTabBarController : UITabBarController<UITabBarControllerDelegate,UIActionSheetDelegate>

{

    UINavigationController *navLogin0;

    UINavigationController *navLogin1;

    UINavigationController *navLogin2;

    UINavigationController *navLogin3;

    UINavigationController *navLogin4;

}

@end

- (void)viewDidLoad

{

    [super viewDidLoad];

    //主页

    HomePageViewController *aHomePageViewController=[[HomePageViewController alloc]init];

    UITabBarItem *item0=[[UITabBarItem alloc]initWithTitle:@"主页" image:[[UIImage imageNamed:@"icon_home1.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"icon_home2.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];

    [item0 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:BLACKCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateSelected];

    [item0 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:GRAYCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateNormal];

    aHomePageViewController.tabBarItem=item0;

    UINavigationController *nav0=[[UINavigationController alloc]initWithRootViewController:aHomePageViewController];

    navLogin0=nav0;

    //消息

    InformationViewController *aInformationViewController=[[InformationViewController alloc]init];

    UITabBarItem *item1=[[UITabBarItem alloc]initWithTitle:@"消息" image:[[UIImage imageNamed:@"icon_message1.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"icon_message2.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];

    [item1 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:BLACKCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateSelected];

    [item1 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:GRAYCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateNormal];

    aInformationViewController.tabBarItem=item1;

    UINavigationController *nav1=[[UINavigationController alloc]initWithRootViewController:aInformationViewController];

    navLogin1=nav1;

    //发布

    PublishViewController *aPublishViewController=[[PublishViewController alloc]init];

    UITabBarItem *item2=[[UITabBarItem alloc]initWithTitle:@"发布" image:[[UIImage imageNamed:@"icon_publish2.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"icon_publish1.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];

    [item2 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:BLACKCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateSelected];

    [item2 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:GRAYCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateNormal];

    aPublishViewController.tabBarItem=item2;

    UINavigationController *nav2=[[UINavigationController alloc]initWithRootViewController:aPublishViewController];

    navLogin2=nav2;

    //朋友

    FriendsViewController *aFriendsViewController=[[FriendsViewController alloc]init];

    UITabBarItem *item3=[[UITabBarItem alloc]initWithTitle:@"朋友" image:[[UIImage imageNamed:@"icon_friend1.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"icon_friend2.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];

    [item3 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:BLACKCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateSelected];

    [item3 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:GRAYCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateNormal];

    aFriendsViewController.tabBarItem=item3;

    UINavigationController *nav3=[[UINavigationController alloc]initWithRootViewController:aFriendsViewController];

    navLogin3=nav3;

    //我的

    MyViewController *aMyViewController=[[MyViewController alloc]init];

    UITabBarItem *item4=[[UITabBarItem alloc]initWithTitle:@"我的" image:[[UIImage imageNamed:@"icon_wo1.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"icon_wo2.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];

    [item4 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:BLACKCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateSelected];

    [item4 setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:GRAYCOLOR,NSForegroundColorAttributeName,[UIFont systemFontOfSize:12],NSFontAttributeName, nil] forState:UIControlStateNormal];

    aMyViewController.tabBarItem=item4;

    UINavigationController *nav4=[[UINavigationController alloc]initWithRootViewController:aMyViewController];

    navLogin4=nav4;

    self.viewControllers = [NSArray arrayWithObjects:nav0,nav1,nav2,nav3,nav4,nil];

    self.delegate=self;

    self.tabBar.backgroundColor = [UIColor clearColor];

}

 3.

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController{

    if ([[NSUserDefaults standardUserDefaults]objectForKey:@"userid"]) {

        //已经登陆

    }

    else

    {

        //用户没登陆

        if (viewController!=navLogin0)

        {

            UIActionSheet* mySheet = [[UIActionSheet alloc]

                                      initWithTitle:nil

                                      delegate:self

                                      cancelButtonTitle:@"取消"

                                      destructiveButtonTitle:nil

                                      otherButtonTitles:@"去绑定社交账号登录",nil];

            mySheet.tag=3000;

            [mySheet showInView:self.view];

        }

        //这儿设置成YES 就会先跳到下个页面 然后弹出UIActionSheet 设置成NO 就会在当前页面 弹出UIActionSheet 

        return NO;

    }

    return YES;

}

- (void)actionSheetCancel:(UIActionSheet *)actionSheet{

    //

}

- (void) actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex{

    if (actionSheet.tag==3000) {

        //登录按钮

        if (buttonIndex==0) {

            NSLog(@"denglu");

            //用户没登陆

            LoginViewController * detailViewController = [[LoginViewController alloc] init];

            detailViewController.hidesBottomBarWhenPushed=YES;

            [[self.viewControllers objectAtIndex:0] pushViewController:detailViewController animated:NO];

            [actionSheet dismissWithClickedButtonIndex:0 animated:YES];

        }

    }

}

-(void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex{

    //

}

-(void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex{

    //

}