先上一張效果圖：

lALPACOG82h0uBDNCKDNBNo_1242_2208.png_620x10000q90g.jpg

下面開(kāi)始說(shuō)一下思路：

第一步；先對(duì)UIView進(jìn)行擴(kuò)展，方便我們獲取它子類的一下屬性娃闲。代碼如下

#import <UIKit/UIKit.h>

@interface UIView (Extension)

@property (nonatomic,assign) CGFloat x;
@property (nonatomic,assign) CGFloat y;
@property (nonatomic,assign) CGFloat width;
@property (nonatomic,assign) CGFloat height;
@property (nonatomic,assign) CGFloat centerX;
@property (nonatomic,assign) CGFloat centerY;
@property (nonatomic,assign) CGSize size;

@end

#import "UIView+Extension.h"

@implementation UIView (Extension)

#pragma mark 重寫(xiě)set get 方法
#pragma mark x
- (void)setX:(CGFloat)x
{
    CGRect frame = self.frame;
    frame.origin.x = x;
    self.frame = frame;
}
- (CGFloat)x
{
    return self.frame.origin.x;
}

#pragma mark y
- (void)setY:(CGFloat)y
{
    CGRect frame = self.frame;
    frame.origin.y = y;
    self.frame = frame;
}
- (CGFloat)y
{
    return self.frame.origin.y;
}

#pragma mark width
- (void)setWidth:(CGFloat)width
{
    CGRect frame = self.frame;
    frame.size.width = width;
    self.frame = frame;
}
- (CGFloat)width
{
    return self.frame.size.width;
}

#pragma mark height
- (void)setHeight:(CGFloat)height
{
    CGRect frame = self.frame;
    frame.size.height = height;
}
- (CGFloat)height
{
    return self.frame.size.height;
}

#pragma mark centerX
- (void)setCenterX:(CGFloat)centerX
{
    CGPoint center = self.center;
    center.x = centerX;
    self.center = center;
}
- (CGFloat)centerX
{
    return self.center.x;
}

#pragma mark centerY
- (void)setCenterY:(CGFloat)centerY
{
    CGPoint center = self.center;
    center.y = centerY;
    self.center = center;
}
- (CGFloat)centerY
{
    return self.center.y;
}

#pragma mark size
- (void)setSize:(CGSize)size
{
    CGRect frame = self.frame;
    frame.size = size;
    self.frame = frame;
}
- (CGSize)size
{
    return self.frame.size;
}

@end

第二步忱详，新建一個(gè)類ZLTabbar围来，繼承自UITabBar

1、.h文件

#import <UIKit/UIKit.h>

typedef void(^IrrBtnSelectedBlock)();
@interface ZLTabbar : UITabBar

//用于監(jiān)聽(tīng)自定義tabbarButton的點(diǎn)擊事件
@property (nonatomic,copy) IrrBtnSelectedBlock selectedIrrBtn;
- (void)didselectedIrrBtnWithBlock:(IrrBtnSelectedBlock)selectedIrrBtn;

@end

這里解釋一下匈睁，我習(xí)慣用block监透，所以這里聲明了一個(gè)block類型。你也可以根據(jù)個(gè)人習(xí)慣航唆，來(lái)使用觀察者或者代理胀蛮。
2、.m文件

#import "ZLTabbar.h"
#import "UIView+Extension.h"

@interface ZLTabbar ()

@property (nonatomic,strong) UIButton *irregularItem;//不規(guī)則的按鈕糯钙，可以放在在中間或者其它任意一個(gè)地方

@end

@implementation ZLTabbar

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        //TODO:加載子視圖
        [self createChildrenViews];
    }
    return self;
}

#pragma mark 創(chuàng)建子視圖
- (void)createChildrenViews
{
    self.backgroundColor = [UIColor whiteColor];

    //TODO:去掉tabbar的分割線
    [self setBackgroundImage:[UIImage new]];
    [self setShadowImage:[UIImage new]];

    self.irregularItem = [UIButton buttonWithType:UIButtonTypeCustom];
    [self.irregularItem setBackgroundImage:[UIImage imageNamed:@"midBtn"] forState:UIControlStateNormal];
    [self.irregularItem setBackgroundImage:[UIImage imageNamed:@"midBtn"] forState:UIControlStateHighlighted];
    self.irregularItem.size = self.irregularItem.currentBackgroundImage.size;
    self.irregularItem.layer.masksToBounds = YES;
    self.irregularItem.layer.cornerRadius = self.irregularItem.width/2;
    [self.irregularItem addTarget:self action:@selector(irregularItemSelcted) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:self.irregularItem];
}

#pragma mark 執(zhí)行和監(jiān)聽(tīng)不規(guī)則按鈕的點(diǎn)擊事件
- (void)irregularItemSelcted
{
    if (self.selectedIrrBtn)
    {
        self.selectedIrrBtn();
    }
}

- (void)didselectedIrrBtnWithBlock:(IrrBtnSelectedBlock)selectedIrrBtn
{
    self.selectedIrrBtn = selectedIrrBtn;
}

#pragma mark layoutSubviews
- (void)layoutSubviews
{
    [super layoutSubviews];

    //TODO:重新排布系統(tǒng)按鈕的位置粪狼，空出需要自定義按鈕的位置，系統(tǒng)按鈕的類型是UITabBarButton
    Class class = NSClassFromString(@"UITabBarButton");

    //TODO:這里設(shè)置自定義tabbarButton的位置
    self.irregularItem.centerX = (self.width * 0.75 + self.irregularItem.width * 0.75);
    self.irregularItem.centerY = self.height - self.irregularItem.height/2;

    NSInteger btnIndex = 0;
    for (UIView *btn in self.subviews)
    {
        if ([btn isKindOfClass:class])
        {
            //TODO:如果是系統(tǒng)的UITabBarButton超营，調(diào)整子控件位置鸳玩，空出自定義UITabBarButton的位置
            //TODO:按鈕寬度為T(mén)abbar寬度平分4塊
            btn.width = self.width/4;
            if (btnIndex < 3)
            {
                //TODO: -3- 在這里為irregularItem的索引值
                btn.x = btn.width * btnIndex;
            }
            else
            {
                btn.x = btn.width * btnIndex + self.irregularItem.width;
            }
            btnIndex ++;

            if (btnIndex == 0)
            {
                btnIndex ++;
            }
        }
    }
    [self bringSubviewToFront:self.irregularItem];
}

#pragma mark 重寫(xiě)hitTest方法，去監(jiān)聽(tīng)irregularItem的點(diǎn)擊演闭，目的是為了讓突出在外面的部分 在點(diǎn)擊時(shí)也有反應(yīng)
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    /**判斷當(dāng)前手指是否點(diǎn)擊到了irregularItem不跟。如果是，則相應(yīng)按鈕點(diǎn)擊米碰；如果是其它窝革，則由系統(tǒng)處理**/
    //當(dāng)前view是否被隱藏？如果隱藏吕座，就不做其他處理了虐译。
    if (self.isHidden == NO)
    {
        //TODO:將當(dāng)前tabbar的觸摸點(diǎn)轉(zhuǎn)換成坐標(biāo)系，轉(zhuǎn)換到irregularItem的身上吴趴，生成一個(gè)新的點(diǎn)
        CGPoint new_point = [self convertPoint:point toView:self.irregularItem];

        //TODO:如果這個(gè)新的點(diǎn)是在irregularItem上漆诽，那么處理點(diǎn)點(diǎn)擊事件最合適的view就是irregularItem
        if ([self.irregularItem pointInside:new_point withEvent:event])
        {
            return self.irregularItem;
        }
    }
    return [super hitTest:point withEvent:event];
}

@end

說(shuō)明：

1.在layoutSubviews方法中，重設(shè)自定義以及系統(tǒng)的tabbarButton的位置。
2.如果不重寫(xiě)hitTest方法厢拭，點(diǎn)擊突出在外面的button會(huì)無(wú)事件響應(yīng)兰英。
3.當(dāng)調(diào)整自定義tabbarButton的位置時(shí)，還有可能需要調(diào)整它的索引值供鸠。此時(shí)畦贸，它的索引值為3；

第三步楞捂，創(chuàng)建tabbarController

.m文件

#import "ZLTabbarController.h"
#import "LeftViewController.h"
#import "RightViewController.h"
#import "MidViewController.h"
#import "ResourceViewController.h"
#import "ZLTabbar.h"
@interface ZLTabbarController ()

@end

@implementation ZLTabbarController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setupTabbar];
}

#pragma mark 設(shè)置tabbar
- (void)setupTabbar
{
    LeftViewController *left = [[LeftViewController alloc]init];
    [self createChildrenVC:left
           childrenVCTitle:@"首頁(yè)"
                     image:[UIImage imageNamed:@"首頁(yè)"]
             selectedImage:[UIImage imageNamed:@"首頁(yè)_S"]];
    ResourceViewController *resource = [[ResourceViewController alloc]init];
    [self createChildrenVC:resource
           childrenVCTitle:@"資源"
                     image:[UIImage imageNamed:@"資源"]
             selectedImage:[UIImage imageNamed:@"資源_S"]];

    RightViewController *right = [[RightViewController alloc]init];
    [self createChildrenVC:right
           childrenVCTitle:@"個(gè)人中心"
                     image:[UIImage imageNamed:@"個(gè)人中心"]
             selectedImage:[UIImage imageNamed:@"個(gè)人中心_S"]];

    ZLTabbar *tabbar = [[ZLTabbar alloc]init];
    tabbar.selectedItem = left.tabBarItem;
    MidViewController *mid = [[MidViewController alloc]init];
    [tabbar didselectedIrrBtnWithBlock:^{
        [self presentViewController:mid animated:YES completion:nil];
    }];
    [self setValue:tabbar forKey:@"tabBar"];
}


#pragma mark 添加子控制器
- (void)createChildrenVC:(UIViewController *)childViewController
         childrenVCTitle:(NSString *)title
                   image:(UIImage *)image
           selectedImage:(UIImage *)selectedImg
{
    //設(shè)置選中時(shí)item的字體顏色
    UIColor *selectedTinColor = [UIColor colorWithRed:60.0/255
                                                green:160.0/255
                                                 blue:220.0/255
                                                alpha:1.0f];
    [[UITabBarItem appearance] setTitleTextAttributes:[NSDictionary dictionaryWithObject:NSForegroundColorAttributeName
                                                                                  forKey:selectedTinColor]
                                             forState:UIControlStateSelected];

    //設(shè)置未選中的image
    UIImage *deselectedImage = image;
    deselectedImage = [deselectedImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    childViewController.tabBarItem.image = deselectedImage;

    //設(shè)置選中的image
    UIImage *selectedImage = selectedImg;
    selectedImage = [selectedImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    childViewController.tabBarItem.selectedImage = selectedImage;

    //設(shè)置tabbarItem文字和圖標(biāo) 之間的距離
    childViewController.tabBarItem.title = title;
//    childViewController.tabBarItem.titlePositionAdjustment = UIOffsetMake(0, MAXFLOAT);

    //添加控制器對(duì)象
    UINavigationController *childNavigationContorller  = [[UINavigationController alloc]initWithRootViewController:childViewController];
    [self addChildViewController:childNavigationContorller];
}
@end

說(shuō)明：

1.我們可通過(guò)tabBarItem.titlePositionAdjustment來(lái)設(shè)置文字與圖表之間的距離薄坏，當(dāng)值為MAXFLOAT時(shí)，這個(gè)方法也起到了隱藏文字的作用寨闹。當(dāng)然胶坠，你可以直接tabBarItem.title設(shè)置為空字符串對(duì)象。
2.我們可以通過(guò)[tabbar didselectedIrrBtnWithBlock:^{ /**在這里做一些操作**/ }];來(lái)響應(yīng)一些操作繁堡。

3涵但、最后把tabbarController的對(duì)象設(shè)置為window的根視圖控制器就可以使用了。詳細(xì)的代碼都在上面了帖蔓，注釋也寫(xiě)的比較清晰矮瘟。如果有不懂的地方可以留言。代碼不足的地方塑娇，還望各位大神多多指教澈侠。