How can I get data from various nodes in a Realtime-database in Flutter? - flutter

Question

I'm trying to display data from a real-time database in my widget, such as a picture, a name, or a message, but I'm not sure how to achieve it from several nodes. Thank you in advance for your assistance.
For add data :
List lists = [];
stream to get data :
final dbRef = FirebaseDatabase.instance
.ref()
.child("chatList")
.child("D1NilPUI6PY0jSA1tk0wRzi6FsO2");
Widget to show data :
_widget() {
return StreamBuilder(
stream: dbRef.onValue,
builder: (BuildContext context, AsyncSnapshot snap) {
if (snap.hasData &&
!snap.hasError &&
snap.data!.snapshot.value != null) {
Map data = snap.data.snapshot.value;
List item = [];
data.forEach((index, data) => item.add({"chatList": index, ...data}));
print("DATA : $item");
if (snap.connectionState == ConnectionState.waiting) {
return const CircularProgressIndicator();
} else {
return ListView.builder(
shrinkWrap: true,
physics: const NeverScrollableScrollPhysics(),
itemCount: item.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(item[index]['content'].toString()),
);
},
);
}
} else {
return const Center(child: Text("No data"));
}
},
);
}
Table structure Images :
Image 1 :
Image 2 :

Answer 1

This code:
final dbRef = FirebaseDatabase.instance
.ref()
.child("chatList")
.child("D1NilPUI6PY0jSA1tk0wRzi6FsO2");
This refers to a node /chatList/D1NilPUI6PY0jSA1tk0wRzi6FsO2 in your database. Since the screenshot doesn't show any data under that exact path, you will get a snapshot without any value from reading it.
If you want to read all nodes under /chatList, you can use that path in the query, and then loop over all the children of the snapshot.
final dbRef = FirebaseDatabase.instance
.ref()
.child("chatList");
dbRef.onValue.listen((event) => {
event.snapshot.children.forEach((child) {
print(child.key);
})
})
Since you have two levels with dynamic keys under chatList, you'll have to use two nested loops to get to the named properties:
final dbRef = FirebaseDatabase.instance
.ref()
.child("chatList");
dbRef.onValue.listen((event) => {
event.snapshot.children.forEach((child) {
print(child.key);
child.children.forEach((child2) {
print(child2.key);
print(child2.child("lastMessage/content").value);
})
})
})