iOS-在UITabBarController上添加中间按钮

有时候我们需要在UITabBarController中间添加一个按钮，并且不需要让他控制VC。我们只需要简单几步就可以实现此效果。

一：继承UITabBarController

@interface NNTabBarController ()
@property (nonatomic, weak) UIButton *composeButton;

@end

@implementation NNTabBarController

#pragma mark - 统一设置所有 UITabBarItem 的文字属性
+ (void)initialize {
    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
    attrs[NSFontAttributeName] = [UIFont systemFontOfSize:12];
    attrs[NSForegroundColorAttributeName] = [UIColor grayColor];
    
    NSMutableDictionary *selectedAttrs = [NSMutableDictionary dictionary];
    selectedAttrs[NSFontAttributeName] = attrs[NSFontAttributeName];
    selectedAttrs[NSForegroundColorAttributeName] = [UIColor colorWithRed:255/255.0 green:125/255.0 blue:0 alpha:1];
    
    UITabBarItem *items = [UITabBarItem appearance];
    [items setTitleTextAttributes:attrs forState:UIControlStateNormal];
    [items setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];
}

二：加载vc和中间按钮

#pragma mark - 初始化
- (instancetype)init {
    if (self = [super init]) {
        [self addChildViewControllers];
        [self addComposeButton];
        
    }
    return self;
}

#pragma mark - 添加所有子控制器
- (void)addChildViewControllers {
    [self addChildViewControllerClassName:@"NNHomePageController" title:@"首页" imageName:@"tabbar_home"];
    [self addChildViewControllerClassName:@"NNFoundController" title:@"发现" imageName:@"tabbar_discover"];
    [self addChildViewController: [[UIViewController alloc] init]];
    [self addChildViewControllerClassName:@"NNMessageController" title:@"消息" imageName:@"tabbar_message_center"];
    [self addChildViewControllerClassName:@"NNMyController" title:@"我的" imageName:@"tabbar_profile"];
}

#pragma mark - 设置所有子控制器
- (void)addChildViewControllerClassName:(NSString *)className title:(NSString *)title imageName:(NSString *)imageName
{
    UIViewController *viewController = [[NSClassFromString(className) alloc] init];
    NNNavigationController *nav = [[NNNavigationController alloc] initWithRootViewController:viewController];
    viewController.title = title;
    viewController.view.backgroundColor = [UIColor whiteColor];
    viewController.tabBarItem.image = [UIImage imageNamed: imageName];
    viewController.tabBarItem.selectedImage = [UIImage imageNamed:[NSString stringWithFormat:@"%@_highlighted", imageName]];
    [self addChildViewController:nav];
}

#pragma mark - 添加中间的按钮
- (void)addComposeButton {
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setImage:[UIImage imageNamed:@"tabBar_publish_icon"] forState:UIControlStateNormal];
    [button setImage:[UIImage imageNamed:@"tabBar_publish_icon_highlighted"] forState:UIControlStateSelected];
    [button addTarget:self action:@selector(composeButtonClick:) forControlEvents:UIControlEventTouchUpInside];
    self.composeButton = button;
    [self.tabBar addSubview:button];
    [self.tabBar bringSubviewToFront:button];
    CGFloat width = self.tabBar.bounds.size.width / self.childViewControllers.count - 2;
    self.tabBar.tintColor = [UIColor colorWithRed:68/255.0 green:173/255.0 blue:159/255.0 alpha:1];
    button.frame = CGRectInset(self.tabBar.bounds, 2 * width, 0);
}

#pragma mark - 点击写文章按钮
- (void)composeButtonClick:(UIButton *)button {
    NSLog(@"\n点击了写文章按钮");
}

三：在视图刚要出现的时候讲将中间按钮置前

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    // 不置前点击中间按钮会导致黑屏
    [self.tabBar bringSubviewToFront:self.composeButton];
}

end