Penanganan Error

Firebase Authentication SDK menyediakan cara sederhana untuk mendeteksi berbagai error yang mungkin terjadi menggunakan metode autentikasi. SDK untuk Flutter menampilkan error ini melalui class FirebaseAuthException.

Setidaknya, code dan message disediakan, tetapi dalam beberapa kasus, properti tambahan seperti alamat email dan kredensial juga disediakan. Misalnya, jika pengguna mencoba login dengan email dan sandi, error yang ditampilkan akan terdeteksi secara eksplisit:

try {
  await FirebaseAuth.instance.signInWithEmailAndPassword(
    email: "barry.allen@example.com",
    password: "SuperSecretPassword!"
  );
} on FirebaseAuthException catch  (e) {
  print('Failed with error code: ${e.code}');
  print(e.message);
}

Setiap metode memberikan berbagai kode dan pesan error, bergantung pada jenis panggilan autentikasi. Reference API memberikan detail terbaru tentang error untuk setiap metode.

Error lain seperti too-many-requests atau operation-not-allowed mungkin ditampilkan jika Anda mencapai kuota Firebase Authentication, atau belum mengaktifkan penyedia autentikasi tertentu.

Menangani Error account-exists-with-different-credential

Jika Anda mengaktifkan setelan One account per email address di Firebase console, saat pengguna mencoba login ke penyedia (seperti Google) dengan email yang sudah ada untuk penyedia pengguna Firebase lain (seperti Facebook), error auth/account-exists-with-different-credential akan ditampilkan beserta class AuthCredential (token ID Google). Untuk menyelesaikan alur login ke penyedia yang dimaksud, pengguna harus login terlebih dahulu ke penyedia yang ada (misalnya Facebook), lalu menautkan akunnya ke AuthCredential sebelumnya (token ID Google).

FirebaseAuth auth = FirebaseAuth.instance;

// Create a credential from a Google Sign-in Request
var googleAuthCredential = GoogleAuthProvider.credential(accessToken: 'xxxx');

try {
  // Attempt to sign in the user in with Google
  await auth.signInWithCredential(googleAuthCredential);
} on FirebaseAuthException catch (e) {
  if (e.code == 'account-exists-with-different-credential') {
    // The account already exists with a different credential
    String email = e.email;
    AuthCredential pendingCredential = e.credential;

    // Fetch a list of what sign-in methods exist for the conflicting user
    List<String> userSignInMethods = await auth.fetchSignInMethodsForEmail(email);

    // If the user has several sign-in methods,
    // the first method in the list will be the "recommended" method to use.
    if (userSignInMethods.first == 'password') {
      // Prompt the user to enter their password
      String password = '...';

      // Sign the user in to their account with the password
      UserCredential userCredential = await auth.signInWithEmailAndPassword(
        email: email,
        password: password,
      );

      // Link the pending credential with the existing account
      await userCredential.user.linkWithCredential(pendingCredential);

      // Success! Go back to your application flow
      return goToApplication();
    }

    // Since other providers are now external, you must now sign the user in with another
    // auth provider, such as Facebook.
    if (userSignInMethods.first == 'facebook.com') {
      // Create a new Facebook credential
      String accessToken = await triggerFacebookAuthentication();
      var facebookAuthCredential = FacebookAuthProvider.credential(accessToken);

      // Sign the user in with the credential
      UserCredential userCredential = await auth.signInWithCredential(facebookAuthCredential);

      // Link the pending credential with the existing account
      await userCredential.user.linkWithCredential(pendingCredential);

      // Success! Go back to your application flow
      return goToApplication();
    }

    // Handle other OAuth providers...
  }
}