CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestore
Shikhar Vaish
Shikhar Vaish

Reputation: 93

How to fetch the data from firestore once and reuse it even after navigating to other screen?

I want to fetch data from firestore and use that to build cards in Flutter using ListView on the homepage. While using the navigation menu to switch between screens, I intend to reuse the data once fetched in a session rather than fetching it from the database every time I return to the homepage. But, this is not happening; The data is fetched from the database every time I go to the homepage.

        FutureBuilder(
          future: databaseService(),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              stringMap = snapshot.data;
            }
            return ListView.builder(
              itemBuilder: (context, index) {
                stringMap.forEach((index, value) => {
                      print("The stringMap is ${stringMap.keys.toList()}"),
                    });
                return HomepageCards(
                  user: widget.user,
                  cardDetails: stringMap[stringMap.keys.toList()[index]],
                );
              },
              itemCount: stringMap.length,
              scrollDirection: Axis.vertical,
              controller: _controller,
              shrinkWrap: true,
            );
          },
        )


  databaseService() async {
    return DatabaseService().streamHomePage(widget.user);
  }

DatabaseService.dart

class DatabaseService {
  final Firestore _db = Firestore.instance;
  HomePage home = new HomePage();
  Map homePageMap = new Map<String, Map<String, dynamic>>();

  /// Query a subcollection
  Future streamHomePage(FirebaseUser user) async {
//   Initialise the model map
    home.homeModel = <String, dynamic>{};
    home.homeModel['driverDetails'] = new Map();

    var ref = _db
        .collection('homepage')
        .document(user.uid)
        .collection('h')
        .document('28032020');
// TODO: Try to use cached data. Also try to find the pattern for switching between server and cache
    await ref.get(source: Source.serverAndCache).then((ref) => {
          ref.data.forEach((index, value) => {
                home.homeModel = value,
                homePageMap[index] = value,
              }),
        });
    return homePageMap;
  }
}

Any leads to make the data once fetched reusable would be highly appreciated.

Upvotes: 1

Views: 561

Answers (1)

Peter Haddad
Peter Haddad

Reputation: 80914

Since you only want to fetch it once and then fetch it from the session, therefore you can just check if the session contains the data or not. Another way is to use shared_preferences, for example:

  SharedPreferences prefs = await SharedPreferences.getInstance();

  databaseService() async {
     await prefs.setBool('retrieved', true);
    return DatabaseService().streamHomePage(widget.user);
  }

Then before executing the FutureBuilder check if retrieved is equal to true using getBool() and retrieve data from the session

Upvotes: 1

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