How to access specific data from firebase - firebase

Question

I am new to firebase and I am wondering how would you access specific data. Ill give you an example, BTW I am using flutter.
Say I am creating data like this. I making a table of posts or I guess in firebase it'd be just a json array. In this json array I have 4 pieces of data state, city, post which as of right now just represents a simple message, and also timestamp.
So my question is how can I get a filtered version of my posts with a given city and state? Is there something special you can do in firebase? or would I have to do the filtering when I am building the list view?
I know FirebaseDatabase().reference().child('posts'); can access all of the posts.
var _firebaseRef = FirebaseDatabase().reference().child('posts');
_firebaseRef.push().set({
"state": state,
"city": city,
"post": post,
"timestamp": DateTime.now().millisecondsSinceEpoch
});

Answer 1

The code in the question means you are adding data, not retrieving. If you want to retrieve data according to a specific city then do the following query:
var dbRef = FirebaseDatabase().reference().child('posts');
dbRef.orderByChild("city").equalTo("city_name").once();
once() returns a Future so you can use the FutureBuilder to get the data from the above query.

Answer 2

Use Future Builder to fetch data to listview
create getPost() method first to return qn
Future getPosts() async {
var firestore = Firestore.instance;
QuerySnapshot qn = await firestore.collection("your_collecttion_name").getDocuments();
return qn.documents;
}
after that use, future builder to fetch data
return Container(
child: FutureBuilder(
future: getPosts(),
builder: (_, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Center(
child: Text("Loading..."),
);
} else {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (_, index) {
return Column(
children: <Widget>[
Text(
snapshot.data[index].data['your_data_field'] //name,age etc..
.toString(),
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500),
),]
),}
),
});