UITabBarController的创建等基本方法

 #import "AppDelegate.h"

 @interface AppDelegate () <UITabBarControllerDelegate>

 @end

 @implementation AppDelegate

 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
     // Override point for customization after application launch.

     // 1.创建window
     self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
     self.window.backgroundColor = [UIColor whiteColor];
     [self.window makeKeyAndVisible];

     // 2.创建UITabBarController对象
     UITabBarController *mainTabBar = [[UITabBarController alloc] init];

     // 创建控制器对象
     UIViewController *firstVC = [[UIViewController alloc] init];
     firstVC.view.backgroundColor = [UIColor cyanColor];

     // 设置tabBarItem
     // 第一种方式：系统样式
     firstVC.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemFeatured tag:];

     // 第二种方式：自定义样式
     UIViewController *secondVC = [[UIViewController alloc] init];
     secondVC.view.backgroundColor = [UIColor orangeColor];

     // 创建图片
     UIImage *secondImg = [UIImage imageNamed:@"carGary@2x"];
     UIImage *selectSecondImg = [UIImage imageNamed:@"carRed@2x"];

     // 设置图片保留原有样式
     secondImg = [secondImg imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
     selectSecondImg = [selectSecondImg imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

     secondVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"two" image:secondImg selectedImage:selectSecondImg];

     UIViewController *thirdVC = [[UIViewController alloc] init];
     thirdVC.view.backgroundColor = [UIColor redColor];
     thirdVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"发现" image:[UIImage imageNamed:@"findGray@2x"] tag:];

     UIViewController *fourthVC = [[UIViewController alloc] init];
     fourthVC.view.backgroundColor = [UIColor greenColor];

     fourthVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"用户" image:[UIImage imageNamed:@"userGray@2x"] tag:];

     UIViewController *fifthVC = [[UIViewController alloc] init];
     fifthVC.view.backgroundColor = [UIColor greenColor];

     fifthVC.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemHistory tag:];

     UIViewController *sixVC = [[UIViewController alloc] init];
     sixVC.view.backgroundColor = [UIColor greenColor];

     sixVC.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemTopRated tag:];

     // 设置控制器数组
     mainTabBar.viewControllers = @[firstVC, secondVC, thirdVC, fourthVC, fifthVC, sixVC];
 //    [mainTabBar addChildViewController:firstVC];
 //    [mainTabBar addChildViewController:secondVC];

     // 3.将UITabBarController对象设置为window的根视图控制器
     self.window.rootViewController = mainTabBar;

     // 设置进入应用选中第几个
     mainTabBar.selectedIndex = ;

 #pragma mark - TabBar的属性
     // 修改字体图标等的选中颜色
     mainTabBar.tabBar.tintColor = [UIColor greenColor];

     // 设置tabBar的半透明与否
     mainTabBar.tabBar.translucent = NO;

     // 设置tabBar的颜色
     mainTabBar.tabBar.barTintColor = [UIColor purpleColor];

     // 改变tabBar的位置
     [secondVC.tabBarItem setTitlePositionAdjustment:UIOffsetMake(, )];

     // 设置消息提示
     thirdVC.tabBarItem.badgeValue = @"99+";

     // 设置代理
     mainTabBar.delegate = self;

     return YES;
 }

 #pragma mark - 实现代理方法
 // 清除提示消息
 - (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {

     viewController.tabBarItem.badgeValue = nil;
 }

 @end