RangeError when querying for Document in Firebase

Question

I'm trying to query for data in Firebase with the following method:

static Future<QuerySnapshot> getUserData(String creatorId) {
    Future<QuerySnapshot> data =  _firestore
        .collection('users')
        .where('creatorId', isEqualTo: creatorId)
        .getDocuments();

    return data;
  }

I'm then trying to access the data via this FutureBuilder:

 body: FutureBuilder(
        future: DatabaseService.getUserData(widget.ride.creatorId),
        //future: DatabaseService.getUserData(widget.ride.creatorId),
        builder: (context, snapshot) {
          // if (!snapshot.hasData) {

          // }
          //User user = User.fromDoc(snapshot.data);

          if (!snapshot.hasData) {
            return Center(
              child: CircularProgressIndicator(
                backgroundColor: Color(0xff192C43),
                valueColor: AlwaysStoppedAnimation(
                  Color(0xff213a59),
                ),
              ),
            );
          }
          User user = User.fromDoc(snapshot.data.documents[0]);

          return SearchCardItemExtended(user: user, ride: widget.ride,);
        },
      ),

There is always only one User with the same creatorId. That is why I am calling the document on [0].

When I tap on the button that calls the FutureBuilder I get the following Exception:

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following RangeError was thrown building FutureBuilder<QuerySnapshot>(dirty, state: _FutureBuilderState<QuerySnapshot>#cff34):
RangeError (index): Invalid value: Valid value range is empty: 0

The relevant error-causing widget was: 
  FutureBuilder<QuerySnapshot> file:///C:/Users/Paul/AndroidStudioProjects/leaf/leaf/lib/screens/search_card_info.dart:61:13
When the exception was thrown, this was the stack: 
#0      List.[] (dart:core-patch/growable_array.dart:149:60)
#1      _SearchCardInfoState.build.<anonymous closure> (package:leaf/screens/search_card_info.dart:80:59)
#2      _FutureBuilderState.build (package:flutter/src/widgets/async.dart)
#3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4334:27)
#4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4223:15)
...
════════════════════════════════════════════════════════════════════════════════════════════════════

A very similar query and FutureBuilder elsewhere in the Code work. This is the other FutureBuilder:

body: FutureBuilder(
        future: DatabaseService.searchRides(origin, destination, date, time),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return Center(
              child: CircularProgressIndicator(
                backgroundColor: Color(0xff192C43),
                valueColor: AlwaysStoppedAnimation(
                  Color(0xff213a59),
                ),
              ),
            );
          }
          if (snapshot.data.documents.length == 0) {
            return Center(
              child: Text(
                'Uppss...\n'
                'Leider wurden keine passenden Fahrten gefunden.\n'
                'Schau doch später noch mal vorbei.',
                textAlign: TextAlign.center,
                style: TextStyle(
                  fontFamily: 'UbuntuLight',
                  fontSize: 14,
                  color: Color(0xffE6EFE9),
                  height: 1.6,
                ),
              ),
            );
          }
          return ListView.builder(
            physics: new BouncingScrollPhysics(),
            itemCount: snapshot.data.documents.length,
            itemBuilder: (BuildContext context, int index) {
              Ride ride = Ride.fromDoc(snapshot.data.documents[index]);

              return SearchCardItem(num: index, ride: ride);
            },
          );
        },
      ),

What could be the problem here?

Answer 1

Jus change your code like this.

 if (snapshot.hasData && snapshot.data.length>0) {
 User user = User.fromDoc(snapshot.data.documents[0]);
                //..Implement what you want here}

You are facing this error because there is no result from firebase then your are trying to call |0]but there is no element at 0. You have to wrap it in a conditinnal way. So it will be executed only when there are more then on user in snapshot.data

Answer 2

Plese check condition snapshot.data.documents.isEmpty or not

if(snapshot.data.documents.length!=0){
          User user = User.fromDoc(snapshot.data.documents[0]);

          return SearchCardItemExtended(user: user, ride: widget.ride,);
          } 

          return new Container();