KBTabbar.h

@interface KBTabbar : UITabBar
@property (nonatomic, strong) UIButton *centerBtn;  //中间凸起按钮
@end

KBTabbar.m

@implementation KBTabbar


- (instancetype)init
{
    self = [super init];
    if (self) 
        UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
        [btn setImage:[UIImage imageNamed:@"plus_Last"] forState:UIControlStateNormal];
        btn.bounds = CGRectMake(0, 0, 64, 64);
        self.centerBtn = btn;
        [self addSubview:btn];
        
 
        
    }
    return self;
}

- (void)layoutSubviews
{
    
    [super layoutSubviews];
    
    self.centerBtn.center = CGPointMake(self.bounds.size.width * 0.5, self.bounds.size.height * 0.3);
    
    int index = 0;
    CGFloat wigth = self.bounds.size.width / 5;
    //通过遍历tabbar的字视图，重新布局tabbar上的按钮
    for (UIView* sub in self.subviews) {
        
        if ([sub isKindOfClass:NSClassFromString(@"UITabBarButton")]) {
            
            sub.frame = CGRectMake(index * wigth, self.bounds.origin.y, wigth, self.bounds.size.height - 2);
            
            index++;
            //index == 2 证明是中间的button ，不做任何操作，空出来
            if (index == 2) {
                index++;
            }
        }
    }
}

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    
    if (self.isHidden == NO) {
        //由于凸起的按钮上部分超出父视图，不会响应本身事件。所有在hitTest方法，使凸起按钮响应把自身事件。
        CGPoint newPoint = [self convertPoint:point toView:self.centerBtn];
        
        if ( [self.centerBtn pointInside:newPoint withEvent:event]) {
            return self.centerBtn;
        }else{
            
            return [super hitTest:point withEvent:event];
        }
    }
    
    else {
        return [super hitTest:point withEvent:event];
    }
}

上面就是自定制的tabbar，下面我们通过kvc来替换掉系统的tabbar。

1、创建继承UITabBarController的KBTabbarController

//KBTabbarController.h
@interface KBTabbarController : UITabBarController
@end

2、在m文件中替换tabbar

@interface KBTabbarController ()

@end

@implementation KBTabbarController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    OneViewController *hvc = [[OneViewController alloc] init];
    [self addChildController:hvc title:@"首页" imageName:@"tab1-heartshow" selectedImageName:@"tab1-heart" navVc:[UINavigationController class]];
    
    TwoViewController *fvc = [[TwoViewController alloc] init];
    [self addChildController:fvc title:@"活动" imageName:@"tab2-doctor" selectedImageName:@"tab2-doctorshow" navVc:[UINavigationController class]];
    
    ThreeViewController *MoreVc = [[ThreeViewController alloc] init];
    [self addChildController:MoreVc title:@"更多" imageName:@"tab4-more" selectedImageName:@"tab4-moreshow" navVc:[UINavigationController class]];
    
    FourViewController *svc = [[FourViewController alloc] init];
    [self addChildController:svc title:@"设置" imageName:@"tab5-file" selectedImageName:@"tab5-fileshow" navVc:[UINavigationController class]];
    
    
    [[UITabBar appearance] setBackgroundImage:[self imageWithColor:[UIColor whiteColor]]];
    //  设置tabbar
    [[UITabBar appearance] setShadowImage:[[UIImage alloc] init]];
    // 设置自定义的tabbar
    [self setCustomtabbar];
    
    
    
}

- (void)setCustomtabbar{

    KBTabbar *tabbar = [[KBTabbar alloc]init];
    
    [self setValue:tabbar forKeyPath:@"tabBar"];

    [tabbar.centerBtn addTarget:self action:@selector(centerBtnClick:) forControlEvents:UIControlEventTouchUpInside];


}

- (void)centerBtnClick:(UIButton *)btn{

    
    NSLog(@"点击了中间");
    
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"提示" message:@"点击了中间按钮" delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];
    
    [alert show];
    
    

}
- (void)addChildController:(UIViewController*)childController title:(NSString*)title imageName:(NSString*)imageName selectedImageName:(NSString*)selectedImageName navVc:(Class)navVc
{
    
    childController.title = title;
    childController.tabBarItem.image = [[UIImage imageNamed:imageName] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    childController.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImageName] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    // 设置一下选中tabbar文字颜色
    
    [childController.tabBarItem setTitleTextAttributes:@{ NSForegroundColorAttributeName : [UIColor darkGrayColor] }forState:UIControlStateSelected];
    
    UINavigationController* nav = [[navVc alloc] initWithRootViewController:childController];
    
    [self addChildViewController:nav];
}


- (UIImage *)imageWithColor:(UIColor *)color{
    // 一个像素
    CGRect rect = CGRectMake(0, 0, 1, 1);
    // 开启上下文
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
    [color setFill];
    UIRectFill(rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;
}