UITabBarController

UITabBarController 是我们⼀个   app 在屏幕下⽅的⼀块，与

UINavigationController   类似，都是⽤来管理多个视图控制器的控制器。⽤UITabBarController能很⽅便的对平级的视图控制器进⾏切换，这些视图控制器之间没有直接的关系，也没有等级关系是   ⼀种平级的关系。  

//  AppDelegate.m
//  UITabBarController
//  Created by cqy on 16/1/20.
//  Copyright © 2016年 程清杨. All rights reserved.
#import "AppDelegate.h"
#import "Head.h"
@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
   
         //1.创建Window
         self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
         self.window.backgroundColor = [UIColor whiteColor];
   
         //a.初始化一个tabBar控制器
         UITabBarController *tb=[[UITabBarController alloc]init];
         //选中字体颜色
          tb.tabBar.tintColor = [UIColor blackColor];
         //背景色
          tb.tabBar.barTintColor = [UIColor whiteColor];

         //设置控制器为Window的根控制器
         self.window.rootViewController=tb;
   
         //b.创建子控制器
         NewViewController *New=[[NewViewController alloc]init];
         UINavigationController *newcontroller = [[UINavigationController alloc]initWithRootViewController:New];
         newcontroller.view.backgroundColor=[UIColor greenColor];
         newcontroller.tabBarItem.title=@"消息";
         newcontroller.tabBarItem.image=[UIImage imageNamed:@"tab_recent_nor"];
         newcontroller.tabBarItem.badgeValue=@"123";
   
         LinkmanViewController *Linkman=[[LinkmanViewController alloc]init];
         Linkman.view.backgroundColor=[UIColor brownColor];
         Linkman.tabBarItem.title=@"联系人";
         Linkman.tabBarItem.image=[UIImage imageNamed:@"tab_buddy_nor"];
   
         DynamicViewController *Dynamic=[[DynamicViewController alloc]init];
   
         Dynamic.tabBarItem.title=@"动态";
         Dynamic.tabBarItem.image=[UIImage imageNamed:@"tab_qworld_nor"];
   
         SetViewController *Set=[[SetViewController alloc]init];
         Set.tabBarItem.title=@"设置";
         Set.tabBarItem.image=[UIImage imageNamed:@"tab_me_nor"];
   
   
          //c.添加子控制器到ITabBarController中
          //c.1第一种方式
         //[tb addChildViewController:c1];
         //[tb addChildViewController:c2];
   
         //c.2第二种方式
         tb.viewControllers=@[newcontroller,Linkman,Dynamic,Set];
   
   
        //2.设置Window为主窗口并显示出来
         [self.window makeKeyAndVisible];
 
    // Override point for customization after application launch.
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

@end

在每⼀个tabBar中，每⼀个标签（每⼀个视图控制器），都⽤⾃⼰配套的navigation来管理⾃⼰的层级关系。也就是，有多少个视图控制器，要想管理⾃⼰视图的层级关系，就要有多少个UINavigationController，每⼀个navigation都只管理⾃⼰的层级关系，跟其他navigation不相⼲。     

13、UIAppearance，⼀键换肤。可以对tabBar和navigationBar换肤。