Flutter /Firebase - Accessing the realtime database

Question

In my flutter project, I need to access the realtime database to get the name of the user when they create a post. This is the code I'm working with:

class PostScreen extends StatelessWidget {
  static const String idScreen = 'post';
  final String name1 = FirebaseDatabase.instance
      .reference()
      .child('users')
      .child(FirebaseAuth.instance.currentUser.uid)
      .child('name1')
      .toString();
  final String name2 = FirebaseDatabase.instance
      .reference()
      .child('users')
      .child(FirebaseAuth.instance.currentUser.uid)
      .child('name2')
      .toString();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FlatButton(
        child: Text('Create Post'),
        onPressed: () {
          MainScreen.posts.add(Post(
            name1: name1,
            name2: name2,
          ));
          Navigator.pushNamed(context, MainScreen.idScreen);
        },
      ),
    );
  }
}


class Post extends StatelessWidget {
  String name1 = '';
  String name2 = '';

  Post({@required name1, @required name2});
  @override
  Widget build(BuildContext context) {
    return Card(
      child: Row(
        children: [
          Text(name1),
          Text(" and "),
          Text(name2),
        ],
      ),
    );
  }
}

What happens though is that the name is left blank and just creates a card that says " and ". What could I be doing wrong? Thank you in advance for your help.

Answer 1

Your code doesn't read anything from the database yet. For that to happen you need to call the once() stream, or listen to the onValue or onChild... streams.

I also recommend simplifying your problem before continuing. So instead of reading the data for the current user (which requires that you have a current user), simply write some hard-coded data at a known location in the database and read that first. That should look something like this:

  final DatabaseReference ref = FirebaseDatabase.instance
      .reference()
      .child('test');  

  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
      stream: ref.onValue,
      builder: (BuildContext context, snapshot) {
        if(snapshot.hasData) => return Text(snapshot.value);
        else if(snapshot.hasError) => return Text("Error");
        else return Text("No data (yet)");
      }
    );
  }

There may be syntax errors in this code, so treat it as an example of an approach instead of a copy/paste solution please. If you find any of such errors, please try to solve them on your own - and edit the answer with any fixes.

Also see:

• How To Use Firebase RTDB with Flutter Stream
• more of these search results

Answer 2

You should be able to do something like this:

DatabaseReference myRef = FirebaseDatabase.instance
  .reference()
  .child('users')
  .child(FirebaseAuth.instance.currentUser.uid)
  .child('name1');
 
StreamBuilder(
 stream: myRef.onValue,
 builder: (context, AsyncSnapshot<Event> snap) {
   if (snap.hasData && !snap.hasError && snap.data.snapshot.value != null) {

   // Handle snapshot data
 
   }
}

If you don't need to continue getting changes from the location you can probably use a future builder and.once() method. Don't have experience with that myself though.