Flutter NotifierProvider 每次更新都会重新构建并且值不更新

我对Riverpod还比较陌生，所以我对NotifierProvider有一个奇怪的问题.这是我的通知者:

@riverpod
class CoachPosition extends _$CoachPosition {
  @override
  int build() {
    logger.e("Build CoachPosition");
    return 0;
  }

  void updatePosition(int position) {
    state = position;
  }
}

这是我用来获取并显示教练列表的小部件(它工作得很好).我有大约5位教练.

 final coachesWidget = ref.watch(fetchCoachPreviewsProvider).when(
      data: (List<CoachPreview> list) {
        return CarouselSlider.builder(
          itemCount: list.length,
          itemBuilder: (BuildContext context, int itemIndex, int pageViewIndex) => _FlipCard(list[itemIndex]),
          options: CarouselOptions(
            height: double.infinity,
            enlargeCenterPage: true,
            enlargeFactor: 0.2,
            onPageChanged: (index, reason) {
              logger.e("onPageChanged: $index");
              ref.read(coachPositionProvider.notifier).updatePosition(index);
            },
          ),
        );
      },
      error: (Object error, StackTrace stackTrace) {
        return const Center(
          child: Icon(Icons.error),
        );
      },
      loading: () {
        return const Center(
          child: CircularProgressIndicator(),
        );
      },
    );

这是我用来判断教练位置的按钮:

          SizedBox(
            height: 48,
            child: ElevatedButton(
              onPressed: () {
                final index = ref.read(coachPositionProvider);
                logger.e("start session with coach index: $index");
              },
              style: ElevatedButton.styleFrom(
                backgroundColor: Colors.white,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(25),
                ),
                elevation: 4.0,
              ),
              child: const Text("Start Session", style: TextStyle(fontSize: 19, color: Colors.black54)),
            ),
          ),

问题是，每当我更改CarouselSlider时，索引就会更改，updatePosition方法就会被调用.然而，日志(log)logger.e("Build CoachPosition");一直被显示.正常吗？据我所知，它应该只调用一次.然后，当我按下"Start Session"按钮时，值是0.这个问题的解决方案是什么？