firestore_query.dart

return new StreamBuilder<QuerySnapshot>(
    stream: Firestore.instance.collection('todo_list').where('finished', isEqualTo: false).snapshots,
    builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (!snapshot.hasData) return new Text('Loading...');
        return new ListView(
          children: snapshot.data.documents.map((DocumentSnapshot document) {
            return new ListTile(
              title: new Row(
                children: <Widget>[
                  new Expanded(child: new Text(document['task'])),
                ],
              )
            );
          }).toList(),
        );
    },
);