Firestore Flutter

String _username = "";
String _age = "";
final TextEditingController _usernameController = new TextEditingController();
final TextEditingController _ageController = new TextEditingController();

Widget build(BuildContext context){
    return Scaffold(
        body: Center(
            child: Column(
                children [
                    TextField(
                        controller: _usernameController,
                        decoration: const InputDecoration(
                            label: Text('Input Username'),
                        )
                    ),
                    SizedBox(height: 10),
                    ElevatedButton(
                        onPressed: sendDatatoFirestore,
                        child: Text('Submit');
                    ),
                    SizedBox(height: 10),
                    TextField(
                        controller: _ageController,
                        decoration: const InputDecoration(
                            label: Text('Input Age'),
                        )
                    ),
                ]
            )
        ),
    )
}

void sendDatatoFirestore(){

    _username = _usernameController.text;
    _age = _ageController.text;

    int age;

    age = try.parseInt(_age);

_firestore.collection("users").add({
    'username': _username,
    'age': age,
    'createdAt': FieldValue.serverTimestamp(),

}).then((docRef){
    ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text("Data sent successfully! ID: ${docRef.id}")),
      );
}).catchError((error){

});

}




@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Firestore Snapshot Example")),
      body: StreamBuilder<QuerySnapshot>(
        stream: FirebaseFirestore.instance.collection('users').snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return Center(child: CircularProgressIndicator()); // Show loading
          }

          var users = snapshot.data!.docs;

          return ListView.builder(
            itemCount: users.length,
            itemBuilder: (context, index) {
              var user = users[index];
              return ListTile(
                title: Text(user['name']),
                subtitle: Text("Age: ${user['age']}"),
              );
            },
          );
        },
      ),
    );
  }