GestureDetector in Stack is not working. Stack 하위에 GestureDetector 미작동시 해결 법

아래와 같은 코드처럼 Stack 안에 GestureDetector가 있으면 작동하지 않는다.

Stack(
      clipBehavior: Clip.none,
      children: [
              Positioned(
          right: 0,
          child: GestureDetector(
            onTap: () {
              todoController.changeCalendarFormat();
            },
            child: Container(
              padding: EdgeInsets.symmetric(
                vertical: 5.h,
                horizontal: 16.w,
              ),
              decoration: BoxDecoration(
                borderRadius: BorderRadius.all(Radius.circular(64.r)),
                border: Border.all(
                  color: AppColor.grey[400] as Color,
                  width: 1,
                ),
              ),
              child: Obx(
                () => Text(
                  todoController.calendarFormatString(),
                ),
              ),
            ),
          ),
        ),

        Obx(
          () => TableCalendar(
            locale: window.locale.toString(),
            calendarFormat: todoController.calendarFormat.value
                ? CalendarFormat.week
                : CalendarFormat.month,
            focusedDay: DateTime.now(),
            firstDay: DateTime(2020),
            lastDay: DateTime(2100),
            headerStyle: HeaderStyle(
              leftChevronVisible: false,
              rightChevronVisible: false,
              formatButtonVisible: false,
            ),
            calendarStyle: CalendarStyle(),
          ),
        ),
      ],
    );

• GestureDetector is not Working
• 

아래 처럼 GestureDetector부분을 Stack의 children 안에서 아래 부분으로 코드 순서만 바꿔주면 작동이 된다.

Stack(
      clipBehavior: Clip.none,
      children: [
        Obx(
          () => TableCalendar(
            locale: window.locale.toString(),
            calendarFormat: todoController.calendarFormat.value
                ? CalendarFormat.week
                : CalendarFormat.month,
            focusedDay: DateTime.now(),
            firstDay: DateTime(2020),
            lastDay: DateTime(2100),
            headerStyle: HeaderStyle(
              leftChevronVisible: false,
              rightChevronVisible: false,
              formatButtonVisible: false,
            ),
            calendarStyle: CalendarStyle(),
          ),
        ),
        Positioned(
          right: 0,
          child: GestureDetector(
            onTap: () {
              todoController.changeCalendarFormat();
            },
            child: Container(
              padding: EdgeInsets.symmetric(
                vertical: 5.h,
                horizontal: 16.w,
              ),
              decoration: BoxDecoration(
                borderRadius: BorderRadius.all(Radius.circular(64.r)),
                border: Border.all(
                  color: AppColor.grey[400] as Color,
                  width: 1,
                ),
              ),
              child: Obx(
                () => Text(
                  todoController.calendarFormatString(),
                ),
              ),
            ),
          ),
        ),
      ],
    );

• GestureDetector is Working!!
•