iOS Tabbar中间添加凸起可旋转按钮功能

//MCTabBarController.m
//添加子控制器
- (void)addChildViewControllers{
 //图片大小建议32*32
 [self addChildrenViewController:[[ViewController alloc] init] andTitle:@"首页" andImageName:@"tab1_n" andSelectImage:@"tab1_p"];
 [self addChildrenViewController:[[ViewController alloc] init] andTitle:@"扩展" andImageName:@"tab2_n" andSelectImage:@"tab2_p"];
 //中间这个不设置东西，只占位
 [self addChildrenViewController:[[ViewController alloc] init] andTitle:@"旋转" andImageName:@"" andSelectImage:@""];
 [self addChildrenViewController:[[ViewController alloc] init] andTitle:@"发现" andImageName:@"tab3_n" andSelectImage:@"tab3_p"];
 [self addChildrenViewController:[[ViewController alloc] init] andTitle:@"我" andImageName:@"tab4_n" andSelectImage:@"tab4_p"];
}
- (void)addChildrenViewController:(UIViewController *)childVC andTitle:(NSString *)title andImageName:(NSString *)imageName andSelectImage:(NSString *)selectedImage{
 childVC.tabBarItem.image = [UIImage imageNamed:imageName];
 childVC.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
 childVC.title = title;
 
 BaseNavigationController *baseNav = [[BaseNavigationController alloc] initWithRootViewController:childVC];
 
 [self addChildViewController:baseNav];
}

#import
@interface MCTabBar : UITabBar
@property (nonatomic, strong) UIButton *centerBtn; //中间按钮
@end
```
```
@implementation MCTabBar
- (instancetype)init{
 if (self = [super init]){
 [self initView];
 }
 return self;
}
- (void)initView{
 _centerBtn = [UIButton buttonWithType:UIButtonTypeCustom];
 // 设定button大小为适应图片
 UIImage *normalImage = [UIImage imageNamed:@"tabbar_add"];
 _centerBtn.frame = CGRectMake(0, 0, normalImage.size.width, normalImage.size.height);
 [_centerBtn setImage:normalImage forState:UIControlStateNormal];
 //去除选择时高亮
 _centerBtn.adjustsImageWhenHighlighted = NO;
 //根据图片调整button的位置(图片中心在tabbar的中间最上部，这个时候由于按钮是有一部分超出tabbar的，所以点击无效，要进行处理)
 _centerBtn.frame = CGRectMake(([UIScreen mainScreen].bounds.size.width - normalImage.size.width)/2.0, - normalImage.size.height/2.0, normalImage.size.width, normalImage.size.height);
 [self addSubview:_centerBtn];
}
//处理超出区域点击无效的问题
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
 UIView *view = [super hitTest:point withEvent:event];
 if (view == nil){
 //转换坐标
 CGPoint tempPoint = [self.centerBtn convertPoint:point fromView:self];
 //判断点击的点是否在按钮区域内
 if (CGRectContainsPoint(self.centerBtn.bounds, tempPoint)){
  //返回按钮
  return _centerBtn;
 }
 }
 return view;
}
```

//MCTabBarController.m
- (void)viewDidLoad {
 [super viewDidLoad];
 
 _mcTabbar = [[MCTabBar alloc] init];
 [_mcTabbar.centerBtn addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
 //选中时的颜色
 _mcTabbar.tintColor = [UIColor colorWithRed:27.0/255.0 green:118.0/255.0 blue:208/255.0 alpha:1];
 //透明设置为NO，显示白色，view的高度到tabbar顶部截止，YES的话到底部
 _mcTabbar.translucent = NO;
 //利用KVC 将自己的tabbar赋给系统tabBar
 [self setValue:_mcTabbar forKeyPath:@"tabBar"];
 
 self.delegate = self;
 [self addChildViewControllers];
}
```

- (void)buttonAction:(UIButton *)button{
 self.selectedIndex = 2;//关联中间按钮
 [self rotationAnimation];
}
//tabbar选择时的代理
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{
 if (tabBarController.selectedIndex == 2){//选中中间的按钮
 [self rotationAnimation];
 }else {
 [_mcTabbar.centerBtn.layer removeAllAnimations];
 }
}
//旋转动画
- (void)rotationAnimation{
 CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
 rotationAnimation.toValue = [NSNumber numberWithFloat:M_PI*2.0];
 rotationAnimation.duration = 3.0;
 rotationAnimation.repeatCount = HUGE;
 [_mcTabbar.centerBtn.layer addAnimation:rotationAnimation forKey:@"key"];
}