Flutter & Firebase Error displaying an document (Array) from firebase on a view - flutter

Question

I am using FireBase to store some data. So far, I was creating several collections.
But, I have understood that more collections I have more Firebase will cost when the application will be in production. Someone told me that I should create a 'General' collection, where I can store several documents in array. I just want to display on several cards, all the contexts of the array "context_Name"
So I have modify my collections and document, but I do not know how to get the same results as before I modify my code.
The error I am getting is type 'List' is not a subtype of type 'String'.
When the exception was thrown, this was the stack:
#0 _Context_List_Sate.build.. (package:lt/Views/Lists/14_contexts_lists_page.dart:217:45)
#1 MappedListIterable.elementAt (dart:_internal/iterable.dart:412:31)
#2 ListIterator.moveNext (dart:_internal/iterable.dart:341:26)
#3 new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:188:27)
#4 new _GrowableList.of (dart:core-patch/growable_array.dart:150:28)
If i understand the error, I do not find how to fix that while displaying all the records, but one by one on a card. Many thanks for your help.
class Context_List_View extends StatefulWidget {
Context_List_View({Key key}) : super(key: key);
#override
_Context_List_Sate createState() => _Context_List_Sate();
}
class _Context_List_Sate extends State<Context_List_View> {
#override
Widget build(BuildContext context) {
void showAddNote() {
TextEditingController _noteField = new TextEditingController();
showDialog(
context: context,
builder: (BuildContext context) {
return CustomAlertDialog(
content: Container(
width: MediaQuery.of(context).size.width / 1.3,
height: MediaQuery.of(context).size.height / 4,
child: Column(
children: [
TextField(
controller: _noteField,
maxLines: 4,
decoration: InputDecoration(
border: const OutlineInputBorder(
borderSide:
const BorderSide(color: Colors.black, width: 1.0),
),
),
),
SizedBox(height: 10),
Material(
elevation: 5.0,
borderRadius: BorderRadius.circular(25.0),
color: Colors.white,
child: MaterialButton(
minWidth: MediaQuery.of(context).size.width / 1.5,
onPressed: () {
Navigator.of(context).pop();
CollectionReference users = FirebaseFirestore.instance
.collection('Users')
.doc(FirebaseAuth.instance.currentUser.uid)
.collection('general');
users
.add({'context_Name': _noteField.text,})
.then((value) => print("User Document Added"))
.catchError((error) =>
print("Failed to add user: $error"));
},
padding: EdgeInsets.fromLTRB(10.0, 15.0, 10.0, 15.0),
child: Text(
'Add Context',
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 20.0,
color: Colors.black,
fontWeight: FontWeight.bold,
),
),
),
)
],
),
),
);
});
}
return Scaffold(
appBar: new AppBar(
title: new Text('Contexts'),
actions: <Widget>[
IconButton(
icon: Icon(
Icons.add_circle_outline,
color: Colors.white,
),
onPressed: () {
showAddNote();
},
),
],
),
drawer: MyMenu(),
backgroundColor: Colors.white,
body: Column(
children: [
Container(
height: MediaQuery.of(context).size.height /1.4,
width: MediaQuery.of(context).size.width,
child: StreamBuilder(
stream: FirebaseFirestore.instance
.collection('Users')
.doc(FirebaseAuth.instance.currentUser.uid)
.collection('general')
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(),
);
}
return ListView(
children: snapshot.data.docs.map((document) {
return Wrap(
children: [Card(
child: SwipeActionCell(
key: ObjectKey(document['context_Name']),
trailingActions: <SwipeAction>[
SwipeAction(
title: "delete",
onTap: (CompletionHandler handler) {
CollectionReference users = FirebaseFirestore
.instance
.collection('Users')
.doc(
FirebaseAuth.instance.currentUser.uid)
.collection('contexts');
users
.doc(document.id)
.delete()
.then((value) => print("Context Deleted"))
.catchError((error) => print(
"Failed to delete Next Action: $error"));
},
color: Colors.red),
],
child: Padding(
padding: const EdgeInsets.all(0.0),
child: ListTile(
leading: ConstrainedBox(
constraints: BoxConstraints(
minWidth: leadingIconMinSize,
minHeight: leadingIconMinSize,
maxWidth: leadingIconMaxSize,
maxHeight: leadingIconMaxSize,
),
child: Image.asset('assets/icons/tag.png'),
),
trailing: IconButton(icon: Icon(Icons.edit), onPressed: ()
{
//EDIT CONTEXT
showDialog(
context: context,
barrierDismissible: true,
builder: (BuildContext context){
return AlertDialog(
title: Text("Edit Context"),
content:
TextFormField(
initialValue: document['context_Name'],
onChanged: (value) {
setState(() {
_newContextName = value;
});
},
),
actions: <Widget>[
FlatButton(
child: Text("OK"),
onPressed: (){
setState(() {
var contextRecordID = (document.id);
FirebaseFirestore.instance
.collection('Users')
.doc(
FirebaseAuth.instance.currentUser.uid)
.collection('general')
.doc(contextRecordID)
.update({
'context_Name':_newContextName,
});
});
Navigator.of(context).pop(true);
},
),//OK Button
FlatButton(
child: Text("Cancel"),
onPressed: (){
Navigator.of(context).pop(false);
},
),//Cancel Button
],
);
});}),
title: Text(
document['context_Name'],
maxLines: 2,
overflow: TextOverflow.ellipsis,
),
),
),
),
),
]
);
}).toList(),
);
}),
),
],
),
// bottomNavigationBar: ,
);
}
}

Answer 1

You need to iterate over the members of the context_Name field instead of iterating over the entire general collection. Change the beginning of the StreamBuilder to the following:
// ... other code
StreamBuilder(
stream: FirebaseFirestore.instance
.collection('Users')
.doc(FirebaseAuth.instance.currentUser.uid)
.collection('general')
.doc('baceZyyYUciEGGADfgOv')
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<DocumentSnapshot> snapshot) {
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(),
);
}
return ListView(
children:
(snapshot.data.get('context_Name') as List<String>)
.map((contextName) {
return Wrap(children: [
Card(
child: SwipeActionCell(
key: ObjectKey(contextName),
// ... other code
You will also have to update the callbacks to the SwipeActions and AlertDialog as the document variable will no longer exists. Also, change
title: Text(
document['context_Name'],
maxLines: 2,
overflow: TextOverflow.ellipsis,
),
to
title: Text(
contextName,
maxLines: 2,
overflow: TextOverflow.ellipsis,
),
(towards the end of the code).