可以自己写UIButton分类重写按钮响应链方法，结合关联对象设置属性来控制button的具体实现方法。

• hitTest中的内部实现面试时可能会用到

//  重新实现hittest方法，实现圆形按钮点击范围
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    if (!self.userInteractionEnabled||self.hidden||self.alpha<0.01) {
        return nil;
    }
    if ([self pointInside:point withEvent:event]) {
        // 遍历当前对象的子视图
        __block UIView *hit = nil;
        [self.subviews enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
                // 坐标转换
            //  convertPoint: toView:是（调用者的point+convertpoint）- toview的point
            //  convertPoint: fromView:是（fromView的point+convertpoint）- 调用者的point
            CGPoint convertPoint = [self convertPoint:point toView:obj];
            // 调用子视图的hittest方法
            hit = [obj hitTest:convertPoint withEvent:event];
            // 如果找到了接受事件的对象，就停止遍历
            if (hit) {
                *stop=YES;
            }
        }];
        if (hit) {
            return hit;
        }else{
            return self;
        }
    }else{
        return nil;
    }
}
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    // 点击的点
    CGFloat x1=point.x;
    CGFloat y1=point.y;
    // 中心
    CGFloat x2=self.frame.size.width/2;
    CGFloat y2=self.frame.size.height/2;
    // 平方差公式
    double dis = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    if (dis<=self.frame.size.width/2) {
        return YES;
    }else{
        return NO;
    }
}

针对超出父view之外的部分，比如按钮点击无响应问题

      原因：响应链会先判断点是否在父view范围内，在父view范围内就正序遍历子视图判断哪个来响应，不在就不响应该点击事件。

//超出父层的按钮部分点击无效果 ---  可通过父类view重写如下方法判断子view能否响应
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    for (UIView *subV in self.subviews) {
        if ([subV isKindOfClass:[UIButton class]]) {
            UIButton *btn=(UIButton *)subV;
            if (CGRectContainsPoint(btn.frame, point)) {
                return YES;
            }
        }
    }
    BOOL ss=[super pointInside:point withEvent:event];
    return ss;
}

在来个CoreAnimation运动动画的btn无法点击办法解决：
自定义子view和自定义父view分别重写- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event和- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event 方法
自定义父view实现：

//超出父层的按钮部分点击无效果 ---  可通过重写如下方法盘点子view能否响应时间
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    if (!self.userInteractionEnabled||self.hidden||self.alpha<0.01) {
        return nil;
    }
    if ([self pointInside:point withEvent:event]) {
        // 遍历当前对象的子视图
        __block UIView *hit = nil;
        [self.subviews enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
             // 看情需要否转换坐标
                // 坐标转换
            //  convertPoint: toView:是（调用者的point+convertpoint）- toview的point
            //  convertPoint: fromView:是（fromView的point+convertpoint）- 调用者的point
//          CGPoint convertPoint = [self convertPoint:point toView:obj];
            // 调用子视图的hittest方法
            hit = [obj hitTest:point withEvent:event];
            // 如果找到了接受事件的对象，就停止遍历
            if (hit) {
                *stop=YES;
            }
        }];
        if (hit) {
            return hit;
        }else{
            return self;
        }
    }else{
        return nil;
    }
}

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    for (UIView *subV in self.subviews) {
        if ([subV isKindOfClass:[UIButton class]]) {
            UIButton *btn=(UIButton *)subV;
            // 通过判断子view的运动layerframe来确定点击范围
            if (CGRectContainsPoint(btn.layer.presentationLayer.frame, point) ) {
                return YES;
            }
        }
    }
    BOOL ss=[super pointInside:point withEvent:event];
    return ss;
}

自定义子view实现：

// 通过判断子view的运动layerframe来确定点击范围
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    UIView *vc=[super hitTest:point withEvent:event];
    if (CGRectContainsPoint(self.layer.presentationLayer.frame, point) ) {
        return self;
    }
    return vc;
}

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    BOOL ss=NO;
    if (CGRectContainsPoint(self.layer.presentationLayer.frame, point) ) {
        ss=YES;
    }else{
        ss=[super pointInside:point withEvent:event];
    }
    return ss;
}

最后送个仿支付宝上下不规则浮动泡泡的动画：

    CABasicAnimation *opacityAnim1 =[CABasicAnimation animationWithKeyPath:@"opacity"];
    opacityAnim1.fromValue = [NSNumber numberWithDouble:1];
    opacityAnim1.toValue =[NSNumber numberWithDouble:.5];
    opacityAnim1.duration=5+(double)arc4random()/0x100000000;// 修改渐变动画时间
    opacityAnim1.repeatCount=MAXFLOAT;
    opacityAnim1.delegate=self;
    opacityAnim1.fillMode =kCAFillModeForwards;
    opacityAnim1.autoreverses=YES;
    opacityAnim1.removedOnCompletion=NO;
    opacityAnim1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    [btn.layer addAnimation:opacityAnim1 forKey:@"LightopacityAnim"];


    CABasicAnimation *shake1Animation = [CABasicAnimation animationWithKeyPath:@"transform.translation.y"];
    double fw1=50+(double)arc4random()/0x100000000;// 修改位移动画距离
    shake1Animation.duration=5+(double)arc4random()/0x100000000;// 修改位移动画时间
    shake1Animation.fromValue = [NSNumber numberWithFloat:-fw1];
    shake1Animation.toValue = [NSNumber numberWithFloat:fw1];
    shake1Animation.autoreverses = YES;
    shake1Animation.repeatCount=MAXFLOAT;
    shake1Animation.fillMode =kCAFillModeForwards;
    shake1Animation.removedOnCompletion=NO;
    shake1Animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    [btn.layer addAnimation:shake1Animation forKey:nil];