如何从 Flutter 中的列表中提取 JSON

我正在try 显示来自FiRestore的数据列表中的ListView.Builder.我像这样获取和存储我的数据

List filterMangaList = [];
Future<List> getFavMangas() async {
    var value = await firestore.collection("users").doc(user.uid).get();
    final favMangasList = value.data()?["fav_manga"];
    filterMangaList.clear();
    for (var i in favMangasList) {
      final mangas = await FirebaseFirestore.instance
          .collection('mangas')
          .where('title', isEqualTo: i)
          .get();
      final filterManga = mangas.docs.map((doc) => doc.data()).toList();
      filterMangaList.add(filterManga);
    }
    return filterMangaList;
  }

我要提取数据的列表是filterMangaList人，如下所示

[[{total_chapter: 361, pic: https://images.pexels.com/photos/213780/pexels-photo-213780.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500, title: My Hero Academia}], [{total_chapter: 700, pic: https://images.pexels.com/photos/213780/pexels-photo-213780.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500, title: Naruto}]] 个

我的ListView.Builder如下所示

FutureBuilder(
  future: getFavMangas(),
  builder: (context, AsyncSnapshot future) {
    if (!future.hasData)
      return Container();
    else {
      var filterMangaList = future.data;
      print(filterMangaList);
      return ListView.builder(
        shrinkWrap: true,
        itemCount: filterMangaList.length,
        itemBuilder: (BuildContext context, int index) {
          return Container(
            child: Text(filterMangaList[index]["title"]),
          );
        },
      );
    }
  }),

但我有一个错误:

_TypeError(‘字符串’类型不是‘index’的‘int’类型的子类型)

我想这是因为我有太多的[]，但我不知道如何解决这个问题.