先上要实现的效果：

要实现的效果.gif

有人问，问什么动画效果这么慢？答案是下图

这里设置慢动画.png

我拿到这个需求的第一反应就是，需要自己写个TabBar了，因为系统的TabBar根本没有这种效果。既然这样，那我们肯定不能继承UITabBar去写了，只能是自己写一个控件

• 1：先把大的布局写出来，一个TabBarVc中包含5个嵌套了NavigationController的控制器，代码就不上了

• 2：移除系统自带的TabBar

pragma mark - 移除掉系统的TabBar上的子控件
- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    // 把系统的tabBar上的按钮干掉
    for (UIView *childView in self.tabBar.subviews) {
        [childView removeFromSuperview];
    }
}

// 移除系统的TabBar
[self.tabBar removeFromSuperview]

• 3：换上我自己写的TabBar,这里的self.btnItems中收集的是系统的UITabItem模型

- (void)setupTabBar
{
    // 移除系统的TabBar，移除后，并不会马上消失，一般在下一次循环时，判断这个对象有没有强引用，没有的话，才销毁
    [self.tabBar removeFromSuperview];
    // 自定义的
    LYTabBar *tabBar = [[LYTabBar alloc] init];
    tabBar.frame = CGRectMake(0, kScreenHeight-64, kScreenWidth, 64);
    tabBar.delegate = self;
    tabBar.items = self.btnItems;
    [self.view addSubview:tabBar];
    self.customTabBar = tabBar;
}

• 4、自己写的TabBar内部实现

.h中

#import <UIKit/UIKit.h>
@class LYTabBar;
@protocol LYTabBarDelegate <NSObject>

- (void)tabBar:(LYTabBar *)tabBar didClickIndex:(NSUInteger)index;

@end

@interface LYTabBar : UIView

// 模型数组(UITabBarItem)
@property (nonatomic, strong) NSArray *items;

/** 代理 */
@property (nonatomic, assign) id<LYTabBarDelegate> delegate;

@end

#pragma mark - 自定义控件
@interface LYCustomTabBarView : UIView

/** title */
@property (nonatomic, strong) UILabel *title;

/** norImg */
@property (nonatomic, strong) UIImageView *norImg;

/** select */
@property (nonatomic, strong) UIImageView *selectImg;

- (instancetype)initWithTitle:(NSString *)title imgName:(UIImage *)norImg selectImgName:(UIImage *)selectImg;

@end

.m中

#import "LYTabBar.h"

#define custom_w  kScreenWidth/5
#define custom_h  64

@interface LYTabBar ()

/** lastNorImg */
@property (nonatomic, strong) UIImageView *lastnorImg;
/** lastselectImg */
@property (nonatomic, strong) UIImageView *lastselectImg;

@end

@implementation LYTabBar

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.backgroundColor = [UIColor yellowColor];
    }
    return self;
}
// 先默认设置64的高度
- (void)setItems:(NSArray *)items
{
    _items = items;
    for (int i = 0; i<items.count; i++) {
        UITabBarItem *item = items[i];
        
        LYCustomTabBarView *custom = [[LYCustomTabBarView alloc] initWithTitle:item.title imgName:item.image selectImgName:item.selectedImage];
        custom.frame = CGRectMake(custom_w*i, 0, custom_w, custom_h);
        [custom.norImg addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(norImgTapAction:)]];
        [custom.selectImg addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(selectImgTapAction:)]];
        [self addSubview:custom];
    }
}

#pragma mark - 动作按钮事件
- (void)norImgTapAction:(UITapGestureRecognizer *)sender
{
    UIImageView *nor = (UIImageView *)[sender view];
    UIImageView *select = [nor.superview viewWithTag:2001];
    [UIView animateWithDuration:0.25 animations:^{
        if (self.lastnorImg&&self.lastselectImg) {
            self.lastselectImg.alpha = 0;
            self.lastnorImg.alpha = 1;
            self.lastselectImg.frame = CGRectMake((custom_w-25)/2, custom_h-20-25, 25, 23);
            self.lastnorImg.frame = CGRectMake((custom_w-25)/2, custom_h-20-25, 25, 23);
        }
        nor.alpha = 0;
        select.alpha = 1;
        select.frame = CGRectMake((custom_w-37.5)/2, 0, 37.5, 34.5);
        nor.frame = select.frame;
        
        self.lastnorImg = nor;
        self.lastselectImg = select;
    }];
    
    if ([self.delegate respondsToSelector:@selector(tabBar:didClickIndex:)]) {
        NSUInteger count = [self.subviews indexOfObject:nor.superview];
        [self.delegate tabBar:self didClickIndex:count];
    }
    
}

- (void)selectImgTapAction:(UITapGestureRecognizer *)sender
{
    UIImageView *select = (UIImageView *)[sender view];
    UIImageView *nor = [select.superview viewWithTag:2000];
    [UIView animateWithDuration:0.25 animations:^{
        if (self.lastnorImg&&self.lastselectImg) {
            self.lastselectImg.alpha = 0;
            self.lastnorImg.alpha = 1;
            self.lastselectImg.frame = CGRectMake((custom_w-25)/2, custom_h-20-25, 25, 23);
            self.lastnorImg.frame = CGRectMake((custom_w-25)/2, custom_h-20-25, 25, 23);
        }
        nor.alpha = 1;
        select.alpha = 0;
        self.lastnorImg = nor;
        self.lastselectImg = select;
    }];
}

@end

#pragma mark - 自定义控件
@implementation LYCustomTabBarView
// 先默认设置64的高度
- (instancetype)initWithTitle:(NSString *)title imgName:(UIImage *)norImg selectImgName:(UIImage *)selectImg
{
    self = [super init];
    if (self) {
        
        UILabel *titleLabel = [[UILabel alloc] init];
        titleLabel.text = title.length?title:@"微信";
        titleLabel.font = [UIFont systemFontOfSize:14.0f];
        titleLabel.textAlignment = NSTextAlignmentCenter;
        titleLabel.frame = CGRectMake(0, custom_h-20, custom_w, 20);
        [self addSubview:titleLabel];
        self.title = titleLabel;
        
        UIImageView *norImgView = [[UIImageView alloc] init];
        norImgView.image = norImg;
        norImgView.userInteractionEnabled = YES;
        norImgView.tag = 2000;
        norImgView.frame = CGRectMake((custom_w-25)/2, self.title.ly_y-25, 25, 23);
        norImgView.contentMode = UIViewContentModeScaleAspectFit;
        [self addSubview:norImgView];
        self.norImg = norImgView;
        
        UIImageView *selectImgView = [[UIImageView alloc] init];
        selectImgView.image = selectImg;
        selectImgView.userInteractionEnabled = YES;
        selectImgView.alpha = 0;
        selectImgView.tag = 2001;
        selectImgView.frame = CGRectMake((custom_w-25)/2, self.title.ly_y-25, 25, 23);
        selectImgView.contentMode = UIViewContentModeScaleAspectFit;
        [self addSubview:selectImgView];
        self.selectImg = selectImgView;
    }
    return self;
}

@end

demo地址