Nesting two stream builders causing bad state error - firebase

Question

I am fetching data from two different firestore collections and this is my code
StreamBuilder(
stream: Firestore.instance.collection('items').snapshots(),
builder: (BuildContext context, snapshot){
if(snapshot.connectionState == ConnectionState.waiting){
return CupertinoActivityIndicator();
}
if(snapshot.data != null){
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context,index){
return Column(
children: <Widget>[
Text(snapshot.data.documents[index]['name']),
Text(snapshot.data.documents[index]['color']),
Text(snapshot.data.documents[index]['lifetime']),
Container(
child: StreamBuilder(
stream: Firestore.instance.collection('users')
.document(userid).collection('Quantity')
.document(snapshot.data.documents[index]['id']).snapshots(),
builder: (BuildContext context, snap){
if(snapshot.connectionState == ConnectionState.waiting){
return CupertinoActivityIndicator();
}
if(snap.data != null){
return Container(
child: Text(snap.data.documents.length)
);
}
},
),
)
],
);
});
}
},
)
It is giving me error but when I use futurebuilder inside streambuilder everything works fine and I also used stream broadcast but it is also giving me same error.
Here is the code which I used for broadcast stream
StreamController _controller = StreamController.broadcast();
Stream getItems() async*{
Firestore.instance.collection('items').snapshots().listen((data){
_controller.add(data);
})
yield* _controller.stream;
}

Answer 1

You shouldn't create a new Stream inside the StreamBuilder. When you do:
StreamBuilder(
stream: Firestore.instance.collection('items').snapshots(),
And
StreamBuilder(
stream: Firestore.instance.collection('users')
.document(userid).collection('Quantity')
.document(snapshot.data.documents[index]['id']).snapshots(),
Each time your build() function is called a new StreamBuilder is created, so Firestore.instance.collection()...snapshots() is called, returning a new Stream each time.
You should convert your widget to a StatefulWidget and initialize your Stream on initState(), passing it as a class variable to your StreamBuilder. The nested StreamBuilder can also be transformed into a StatefulWidget and created in place, but initialized on the same manner. Just pay attention that you might need a Key for showing it correctly on a ListView.
Also if you want to convert a Single Subscription Stream to a Broadcast Stream you just have to call asBroadcastStream to convert it.