Firebase Streambuilder - firebase

Question

I have a map in Firebase Database like this,
'abc#gmail.com' : { food order }
I want to create a stream of this data to update widgets when a new order is placed.
I tried using the below code but it is giving error.
DocumentSnapshot has no instance getter 'length'
StreamBuilder(
stream: Firestore.instance.collection('admin').document('current-orders').snapshots(),
builder: (context, snapshot) {
return snapshot.hasData?Column(
children: <Widget>[
Expanded(
child: Container(
child: Padding(
padding: EdgeInsets.all(10),
child: ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (context, uid) {
return Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
snapshot.data.keys.toList()[uid],
style: TextStyle(
fontSize: 18, fontWeight: FontWeight.bold),
),
RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(30)),
color: Colors.blue[200],
child: Text(
'Order Ready',
style: TextStyle(color: Colors.black54),
),
onPressed: () {},
),
],
),
ListView.builder(
shrinkWrap: true,
physics: ClampingScrollPhysics(),
itemCount: snapshot.data.values.keys.toList().length,
itemBuilder: (context, orderID) {
return Text(
'${snapshot.data.values.keys[orderID].toString()} : ${snapshot.data.values.values[orderID].toString()}',
//'${_currentOrders[uid].keys.toList()[orderID]} : ${_currentOrders[uid].values.toList()[orderID]}',
style: TextStyle(fontSize: 16),
);
},
),
Padding(
padding: EdgeInsets.only(top: 10),
child: Container(
color: Colors.grey,
height: 1,
),
)
],
);
},
),
),
),
),
],
):Center(child: Text('No orders right now', style: TextStyle(fontSize: 30, color: Colors.black54),),);
}
);
Thank you.