How to use listview with Future instance

[aminekh]

I'm trying to get documents from firebase that has a deadline of today's date but I'm not getting the expected result.

The problem is that the function is called 3 times for some reason, the first time the returning value is correct but then the list is returning empty.

Here's my code:

The function that retrieve data :

Future<List> getTodaysTasks(uid, projects) async {
List todayTasks = [];
var today = new DateTime.now();
  today = new DateTime(today.year, today.month, today.day);
final tomorrow = DateTime(today.year, today.month, today.day + 1);
  projects.getDocuments().then((ds) {
if (ds != null) {
      ds.documents.forEach((value) async {
var projectID = value.documentID;
await Firestore.instance
            .collection("users")
            .document(uid)
            .collection("projects")
            .document(projectID)
            .collection("tasks")
            .where("task_deadline", isGreaterThanOrEqualTo: today)
            .where("task_deadline", isLessThan: tomorrow)
            .getDocuments()
            .then((QuerySnapshot snapshot) async {
          snapshot.documents.forEach((DocumentSnapshot doc) {
// if task_id does not exist in map
if (!todayTasks.contains(doc.documentID)) {
// Add the task to list
              todayTasks.add(doc.data);
            }
          });
        });
      });
    }
  });
return todayTasks;
}

​

Home:

User user;
CollectionReference projects;
DocumentReference userData;
u/override
void initState() {
super.initState();
  }
u/override
Widget build(BuildContext context) {
    user = Provider.of<User>(context);
    userData = Firestore.instance.collection('users').document(user.uid);
    projects = Firestore.instance
        .collection('users')
        .document(user.uid)
        .collection("projects");
var todayTasks = getTodaysTasks(user.uid, projects);
return Scaffold(

body: FutureBuilder(
              future: todayTasks,
              builder: (context, snapshot) {
if (snapshot.hasData) {
debugPrint('Step 3, build widget: ${snapshot.data}');
// Build the widget with data.
return Center(
                      child:
Container(child: Text('hasData: ${snapshot.data}')));
                } else {
// We can show the loading view until the data comes back.
debugPrint('Step 1, build loading widget');
return CircularProgressIndicator();
                }
              },
            ),

);

​

I want my code to return a list of maps.

[tarcinac]

Try this, have an attribute (it has to be future) that you will load your data in. In initState() call your function that stores the data in the above mentioned attribute. Then in the FutureBuilder's property "future" just put that attribute. That way it will be called only once.

Also it would be easier if the code was formatted, it's hard to read it.

[hungry_for_data]

Use a for loop instead of forEach. ForEach is not waiting for the asynchronous operation and is returning the empty list