自定义UITabBarController，并设为窗口的根控制器

我们这里不用Main.storyBoard作为程序的主窗口，我们采用代码来自己创建窗口。

下面来到AppDelegate.m，#import "TabBarController.h"（这是我们自定义的UITabBarController，继承自UITabBarController）

在程序启动方法里创建窗口，并设置窗口的根控制器为我们自定义的TabBarController

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {        // 创建窗口    self.window = [[UIWindow alloc] init];    self.window.frame = [UIScreen mainScreen].bounds;    // 设置窗口的根控制器    self.window.rootViewController = [[TabBarController alloc] init];;        // 显示窗口    [self.window makeKeyAndVisible];        return YES;}

2.在自定义的UITabBarController里，设置UITabBarItem的文字属性，添加tabBarController的子控制器，替换tabBar为自定义的tabBar

////  TabBarController.m#import "TabBarController.h"#import "TabBar.h"#import "EssenceViewController.h"#import "NewViewController.h"#import "FriendTrendsViewController.h"#import "MeViewController.h"@interface TabBarController ()@end@implementation TabBarController- (void)viewDidLoad {    [super viewDidLoad];        // 通过appearance统一设置UITabBarItem的文字属性    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];    attrs[NSFontAttributeName] = [UIFont systemFontOfSize:12];    attrs[NSForegroundColorAttributeName] = [UIColor grayColor];        NSMutableDictionary *selectedAttrs = [NSMutableDictionary dictionary];    selectedAttrs[NSFontAttributeName] = [UIFont systemFontOfSize:12];    selectedAttrs[NSForegroundColorAttributeName] = [UIColor darkGrayColor];        // 拿到UITabBarItem的appearance    UITabBarItem *item = [UITabBarItem appearance];    [item setTitleTextAttributes:attrs forState:UIControlStateNormal];    [item setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];        // 给tabBarController添加子控制器    [self setupChildVc:[[EssenceViewController alloc] init] title:@"精华" image:@"tabBar_essence_icon" selectedImage:@"tabBar_essence_click_icon"];    [self setupChildVc:[[NewViewController alloc] init] title:@"新帖" image:@"tabBar_new_icon" selectedImage:@"tabBar_new_click_icon"];    [self setupChildVc:[[FriendTrendsViewController alloc] init] title:@"关注" image:@"tabBar_friendTrends_icon" selectedImage:@"tabBar_friendTrends_click_icon"];    [self setupChildVc:[[MeViewController alloc] init] title:@"我" image:@"tabBar_me_icon" selectedImage:@"tabBar_me_click_icon"];        // 更换为自定义的tabBar//    self.tabBar = [[TabBar alloc] init]; //tabBar为只读属性，所以我们下面采用KVC的方式    [self setValue:[[TabBar alloc] init] forKey:@"tabBar"];}/** *  初始化子控制器 */- (void)setupChildVc:(UIViewController *)vc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage {    // 设置文字和图片    vc.tabBarItem.title = title;    vc.tabBarItem.image = [UIImage imageNamed:image];    vc.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];    vc.view.backgroundColor = [UIColor colorWithRed:arc4random_uniform(100)/100.0 green:arc4random_uniform(100)/100.0  blue:arc4random_uniform(100)/100.0  alpha:1.0];        // 添加为子控制器    [self addChildViewController:vc];}@end

3.在自定义的UITabBar里，我们要创建一个特殊的按钮，然后要调整tabBar上所有UITabBarButton的布局

#import "TabBar.h"@interface TabBar()/** 发布按钮 */@property(nonatomic,weak)UIButton *publishButton;@end@implementation TabBar- (instancetype)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        UIButton *publishButton = [UIButton buttonWithType:UIButtonTypeCustom];        [publishButton setBackgroundImage:[UIImage imageNamed:@"tabBar_publish_icon"] forState:UIControlStateNormal];        [publishButton setBackgroundImage:[UIImage imageNamed:@"tabBar_publish_click_icon"] forState:UIControlStateHighlighted];        [self addSubview:publishButton];        self.publishButton = publishButton;    }    return self;}- (void)layoutSubviews {    [super layoutSubviews];        // 设置 发布按钮 的frame    self.publishButton.bounds = CGRectMake(0, 0, self.publishButton.currentBackgroundImage.size.width, self.publishButton.currentBackgroundImage.size.height);    self.publishButton.center = CGPointMake(self.frame.size.width * 0.5, self.frame.size.height * 0.5);       // 设置其他UITabBarButton的frame    CGFloat buttonY = 0;    CGFloat buttonW = self.frame.size.width / 5;    CGFloat buttonH = self.frame.size.height;    NSInteger index = 0;    for (UIView *button in self.subviews) {        // 排除发布按钮//        if(![button isKindOfClass:NSClassFromString(@"UITabBarButton")]) continue;        if(![button isKindOfClass:[UIControl class]] || button == self.publishButton) continue;                // 计算按钮的x值        CGFloat buttonX = buttonW * ((index>1) ? (index+1) : index);        button.frame = CGRectMake(buttonX, buttonY, buttonW, buttonH);                // 增加索引        index++;    }}@end

最后效果：