Вы можете использовать этот код для регистрации пользователя в Cloud Firestore
final FirebaseAuth _auth = FirebaseAuth.instance;
_auth
.createUserWithEmailAndPassword(
email: _myEmail, password: _myPassword)
.catchError((e) {
showDialog(
context: context,
builder: (context) {
return CupertinoAlertDialog(
title: Text('Error Occured'),
content: Text(e.toString()),
actions: <Widget>[
CupertinoButton(
child: Text('Ok'),
onPressed: () => Navigator.of(context).pop())
],
);
});
FirebaseAuth.instance
.signInWithEmailAndPassword(email: _myEmail, password: _myPassword)
.catchError((e) {
showDialog(
context: context,
builder: (context) {
return CupertinoAlertDialog(
title: Text('Error Occured'),
content: Text(e.toString()),
actions: <Widget>[
CupertinoButton(
child: Text('Ok'),
onPressed: () => Navigator.of(context).pop())
],
);
});