自定义放大 TabBar

下面是效果图：

效果图

要实现上面的效果方法有好多种，今天我们用原生的UITabBar来做。
注：这里有一个很小的知识点需要注意一下就是UITabBarItem 是UIBarItem 的子类，直接继承自其。理解这个有助于更好的理解具体实现。
其实实现起来的大致步骤为：
一、item突出显示（偏移）
二、item手势响应处理

item突出显示（偏移）

第一步很简单。创建一个UITabBarController并添加子控制器。

.h
@interface TabbarVC : UITabBarController

@end

.m
-(void)addControllers{
    OneVC *one = [[OneVC alloc]init];
    UINavigationController *navOne = [[UINavigationController alloc]initWithRootViewController:one];
    navOne.tabBarItem = [self getTabBarItemWithTitle:@"第一个" image:[UIImage imageNamed:@"动态"] selectImage:[UIImage imageNamed:@"动态hober"] tag:1];
    
    TwoVC *two = [[TwoVC alloc]init];
    UINavigationController *navTwo = [[UINavigationController alloc]initWithRootViewController:two];
    navTwo.tabBarItem = [self getTabBarItemWithTitle:@"第二个" image:[UIImage imageNamed:@"我的"] selectImage:[UIImage imageNamed:@"我的hover"] tag:2];
    
    ThreeVC *three = [[ThreeVC alloc]init];
    UINavigationController *navThree = [[UINavigationController alloc]initWithRootViewController:three];
    navThree.tabBarItem = [self getTabBarItemWithTitle:@"第三个" image:[UIImage imageNamed:@"展示"] selectImage:[UIImage imageNamed:@"展示hover"] tag:3];

    
    FourVC *four = [[FourVC alloc]init];
    UINavigationController *navFour = [[UINavigationController alloc]initWithRootViewController:four];
    navFour.tabBarItem = [self getTabBarItemWithTitle:@"第四个" image:[UIImage imageNamed:@"训练"] selectImage:[UIImage imageNamed:@"训练hover"] tag:4];
    
    FiveVC *five = [[FiveVC alloc]init];
    UINavigationController *navFive = [[UINavigationController alloc]initWithRootViewController:five];
    navFive.tabBarItem = [self getTabBarItemWithTitle:@"第四个" image:[UIImage imageNamed:@"收藏灰"] selectImage:[UIImage imageNamed:@"收藏"] tag:5];
    self.viewControllers = @[navOne,navTwo,navThree,navFour,navFive];
}

-(UITabBarItem *)getTabBarItemWithTitle:(NSString *)title image:(UIImage *)image selectImage:(UIImage *)selectImage tag:(NSInteger)tag{
    UITabBarItem *item = [[UITabBarItem alloc]initWithTitle:title image:image tag:tag];
    item.selectedImage = selectImage;
    return item;
}

紧接着我们实现UITabBarController 的viewWillLayoutSubviews方法，获取到自己的tabBar上的指定UITabBarItem ，然后拿到UITabBarItem上的imageView视图，设置偏移量，并添加点击事件，做出响应事件的处理。

-(void)viewWillLayoutSubviews{
    [super viewWillLayoutSubviews];
    
    UITabBarItem *tabbarItem = self.tabBar.items[2];
    tabbarItem.imageInsets = UIEdgeInsetsMake(-25, 0, 0, 0);
    
    UIImageView *imageView = [tabbarItem lgj_imageView];
    if (imageView && !imageView.userInteractionEnabled) {
        imageView.userInteractionEnabled = YES;
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(mittileTap)];
        [imageView addGestureRecognizer:tap];
    }
}

-(void)mittileTap{
    self.selectedIndex = 2;
}

item手势响应处理

接下来创建UIBarItem、UITabBarItem和UITabBar的分类
UIBarItem+LGJBarItem.h

#import <UIKit/UIKit.h>

@interface UIBarItem (LGJBarItem)

@property(nonatomic,nullable,weak,readonly)UIView  *lgj_view;

@end


#import "UIBarItem+LGJBarItem.h"

@implementation UIBarItem (LGJBarItem)

-(UIView *)lgj_view{
    return [self valueForKey:@"view"];
}

@end

UITabBarItem+LGJBarItem.h

#import <UIKit/UIKit.h>

@interface UITabBarItem (LGJTabBarItem)

@property(nonatomic, copy) void (^lgj_doubleTapBlock)(UITabBarItem *tabBarItem, NSInteger index);

- (UIImageView *)lgj_imageView;

+ (UIImageView *)lgj_imageViewInTabBarButton:(UIView *)tabBarButton;


@end


#import "UITabBarItem+LGJTabBarItem.h"
#import "UIBarItem+LGJBarItem.h"
#import <objc/runtime.h>
@implementation UITabBarItem (LGJTabBarItem)


- (UIImageView *)lgj_imageView {
    return [self.class lgj_imageViewInTabBarButton:self.lgj_view];
}

+ (UIImageView *)lgj_imageViewInTabBarButton:(UIView *)tabBarButton {
    if (!tabBarButton ) {
        return nil;
    }
    for (UIView *subView in tabBarButton.subviews) {
        if ([NSStringFromClass([subView class]) isEqualToString:@"UITabBarSwappableImageView"]) {
            return (UIImageView *)subView;
        }
        NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
        CFShow(CFBridgingRetain(infoDictionary));
        NSString *app_Version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
        float version = [app_Version floatValue];
        
        if (version < 10) {
            // iOS10以前，选中的item的高亮是用UITabBarSelectionIndicatorView实现的，所以要屏蔽掉
            if ([subView isKindOfClass:[UIImageView class]] && ![NSStringFromClass([subView class]) isEqualToString:@"UITabBarSelectionIndicatorView"]) {
                return (UIImageView *)subView;
            }

        }
    }
    return nil;
}


static char kAssociatedObjectKey_doubleTapBlock;

- (void)setLgj_doubleTapBlock:(void (^)(UITabBarItem *, NSInteger))gs_doubleTapBlock {
    objc_setAssociatedObject(self, &kAssociatedObjectKey_doubleTapBlock, gs_doubleTapBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (void (^)(UITabBarItem *, NSInteger))lgj_doubleTapBlock {
    return (void (^)(UITabBarItem *, NSInteger))objc_getAssociatedObject(self, &kAssociatedObjectKey_doubleTapBlock);
}


@end

UITabBar+LGJBarItem.h

#import <UIKit/UIKit.h>

@interface UITabBar (LGJTabBar)

@end


#import "UITabBar+LGJTabBar.h"
#import "UITabBarItem+LGJTabBarItem.h"
@implementation UITabBar (LGJTabBar)

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    if (!self.isUserInteractionEnabled || self.isHidden || self.alpha <= 0.01) {
        return nil;
        
    }
    if (self.items.count < 2) {
        return [super hitTest:point withEvent:event];
        
    }
    UITabBarItem *item = self.items[2];
    UIImageView *itemImageView = [item lgj_imageView];
    if (!itemImageView) {
        return [super hitTest:point withEvent:event];
        
    }
    UIView *view = [super hitTest:point withEvent:event];
    if (view == nil){
        //转换坐标
        CGPoint tempPoint = [itemImageView convertPoint:point fromView:self];
        //判断点击的点是否在按钮区域内
        if (CGRectContainsPoint(itemImageView.bounds, tempPoint)){ //返回按钮
            return itemImageView;
            
        }
        //****************** 或者使用这个方法 ****************
        //判断如果这个新的点是在发布按钮身上，那么处理点击事件最合适的view就是发布按钮
        if ([itemImageView pointInside:point withEvent:event]) {
            return itemImageView;
            
        }else{
            //如果点不在发布按钮身上，直接让系统处理就可以了
            return [super hitTest:point withEvent:event];
        }
    }
    return view;
}

@end

以上工作完成，一个突出的TabBar就出现了，，，，