I have a function in which I add StreamBuilder(s) into a List, then I load these StreamBuilder(s) inside a Column, this approach is really memory consuming as all of the List is loaded at once, is there a way to do this in another way?

My showList function:

showList() {
    List<Widget> theList= [];
    for (CountryModel country in _allCountries) {
      theList.add(StreamBuilder(
      stream:FirebaseFirestore.instance.collection('user').doc(country.Id).snapshots(),
          builder: (BuildContext context, AsyncSnapshot snapshot) {
            if (snapshot.hasData) {
              xModel user = UserModel.fromDoc(snapshot.data);
              return CountryWidget(
                  country: country,
                  viewer: user.id as String,);
            } else {
              return SizedBox.shrink();
            }
          }));
    }
    return theList;
  }

In my Scaffold I have a Column where I use the spread operator to load a list into children[].

Column(
  children: <Widget>[
    ...showList()
  ],
),

CodePudding user response：

Try the following code:

ListView.builder(
  itemCount: _allCountries.length   _anotherList.length,
  itemBuilder: (context, index) {
    if (index >= _allCountries != true) {
      final CountryModel country = _allCountries[index];
      return StreamBuilder(
        stream: FirebaseFirestore.instance.collection('user').doc(country.Id).snapshots(),
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          if (snapshot.hasData) {
            xModel user = UserModel.fromDoc(snapshot.data);
            return CountryWidget(
              country: country,
              viewer: user.id as String,
            );
          } else {
            return SizedBox.shrink();
          }
        }
        final item = _anotherList[index];
        return widget;
      },
    );
  },
),