How to get another users ID from Firebase in Flutter? - firebase

Question

i'm trying to add user in my contacts by writing his uid from firebase. I need to write users id in textfield and on pressing button i need to firebase check this uid, and if it's exists, my app needs to add it in contacts. Is there any solutions? p.s i'm making messenger app and it's "Add new contact" function. It would be nice if someone tells me how to create chat using their ID or create separate "chat id" which would be same to 2 users. btw i'm using realtime database

Answer 1

To check if the user exsits, you can do something like this:
final users = FirebaseFirestore.instance.collection('users');
final userDoc =
await users.doc('PUT THE UID TO SEARCH FOR HERE').get();
if (userDoc.exists) {
// do something
}
To make this reusable convert it to a function:
Future<bool> userExists(String uid) async {
final users = FirebaseFirestore.instance.collection('users');
final userDoc =
await users.doc(uid).get();
return userDoc.exists;
}
Now you can call the function with any uid:
bool _userExists = await userExists('UID');
Here is a full code example:
import 'package:flutter/material.dart';
void main() {
runApp(App());
}
class App extends StatefulWidget {
#override
_AppState createState() => new _AppState();
}
class _AppState extends State<App> {
// This key is used to control the SnackBars
final key = GlobalKey<ScaffoldMessengerState>();
final textCtrlr = TextEditingController();
bool isLoading = false;
#override
void dispose() {
super.dispose();
textCtrlr.dispose();
}
Future<bool> userExists(String uid) async {
final users = FirebaseFirestore.instance.collection('users');
final userDoc = await users.doc(uid).get();
return userDoc.exists;
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: ScaffoldMessenger(
key: key, // Assign the key to the ScaffoldMessenger
child: Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: SizedBox(
child: TextFormField(
controller: textCtrlr,
),
width: 200.0,
),
),
isLoading
? const SizedBox(
child: CircularProgressIndicator(
strokeWidth: 2.0,
),
width: 20.0,
height: 20.0,
)
: ElevatedButton(
onPressed: () async {
final uid = textCtrlr.text;
setState(() => isLoading = false);
final bool _userExists = await userExists(uid);
setState(() => isLoading = false);
if (_userExists) {
// The user exists and can
// be added to contacts
key.currentState?.showSnackBar(
SnackBar(
content: Text(
'User added!',
),
backgroundColor: Colors.green,
behavior: SnackBarBehavior.floating,
),
);
return;
}
// The user doesn't exist
key.currentState?.showSnackBar(
SnackBar(
content: Text(
'The user doesn\'t exist',
),
backgroundColor: Theme.of(context).errorColor,
behavior: SnackBarBehavior.floating,
),
);
},
child: const Text('Search for user'),
),
],
),
),
),
),
);
}
}