关于UITabBarController显示，定义UITabBar的显示样式

为了解决：UITabBarController 显示不按照系统的样式走，按照自己的意愿来显示出来

步骤：

1：定义UITabBarController ：

     UITabBarController *tabBarController = [[UITabBarController alloc]initWithNibName:nil bundle:nil];

     tabBarController.viewControllers = [[NSArray alloc] initWithObjects:oneNav,twoNav,threeNav,fourNav, nil];

     // 得到UITabBar

     UITabBar *tabBar = tabBarController.tabBar;

    // 得到每个UITabBarItem

    UITabBarItem *aTabBarItem = [tabBar.items objectAtIndex:0];

    UITabBarItem *bTabBarItem = [tabBar.items objectAtIndex:1];

    UITabBarItem *cTabBarItem = [tabBar.items objectAtIndex:2];

    UITabBarItem *dTabBarItem = [tabBar.items objectAtIndex:3];

    aTabBarItem.title = @"aaa";

    bTabBarItem.title = @"bbb";

    cTabBarItem.title = @"ccc";

    dTabBarItem.title = @"ddd";

    // 选中与不选中的小图片

    [aTabBarItem setFinishedSelectedImage:[UIImage imageNamed:@"tab_featured_seclected"] withFinishedUnselectedImage:[UIImage imageNamed:@"tab_featured"]];

    [bTabBarItem setFinishedSelectedImage:[UIImage imageNamed:@"tab_free_seclected"] withFinishedUnselectedImage:[UIImage imageNamed:@"tab_free"]];

    [cTabBarItem setFinishedSelectedImage:[UIImage imageNamed:@"tab_top_seclected"] withFinishedUnselectedImage:[UIImage imageNamed:@"tab_top"]];

    [dTabBarItem setFinishedSelectedImage:[UIImage imageNamed:@"tab_more_seclected"] withFinishedUnselectedImage:[UIImage imageNamed:@"tab_more"]];

   UIImage* tabBarBackground = [self scaleImage:[UIImage imageNamed:@"top_bg.png"]];

    // 修改UITabBar的背景颜色

    [[UITabBar appearance] setBackgroundImage:[tabBarBackground resizableImageWithCapInsets:UIEdgeInsetsZero resizingMode:UIImageResizingModeStretch]];

    // 修改选中后的背景图

    [[UITabBar appearance] setSelectionIndicatorImage:[UIImage imageNamed:@"btnadd3"]];

    // 字体的在正常情况下的显示颜色

    [[UITabBarItem appearance] setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:

                                                       [UIColor whiteColor], UITextAttributeTextColor,

                                                       nil] forState:UIControlStateNormal];

    

    // 字体在选中情况下的显示颜色

    [[UITabBarItem appearance] setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:

                                                       [UIColor blueColor], UITextAttributeTextColor,

                                                       nil] forState:UIControlStateSelected];