Question

I don’t understand how method confirmCredentials works. I’ve never seen any options in the Android UI like “Confirm Credentials” or something like, there are only “Create account” and “Remove account”.

Answer 1

Its used if you want to use the Gmail account on the device as a verification method.
NFCSecure uses it when you open the app, forcing you to login with your gmail.

public void verifyAuth(Bundle b) throws IllegalArgumentException {
    accountManager.confirmCredentials(getImportantAccount(importantEmail), b, (Activity) c, new OnConfirmed(), null);
}


public void attemptLogin() {
    mEmailView.setError(null);
    mPasswordView.setError(null);

    mEmail = mEmailView.getText().toString();
    mPassword = mPasswordView.getText().toString();

    boolean cancel = false;
    View focusView = null;

    if (TextUtils.isEmpty(mPassword)) {
        mPasswordView.setError(getString(R.string.error_field_required));
        focusView = mPasswordView;
        cancel = true;
    } else if (mPassword.length() < 4) {
        mPasswordView.setError(getString(R.string.error_invalid_password));
        focusView = mPasswordView;
        cancel = true;
    }

    if (TextUtils.isEmpty(mEmail)) {
        mEmailView.setError(getString(R.string.error_field_required));
        focusView = mEmailView;
        cancel = true;
    } else if (!mEmail.contains("@")) {
        mEmailView.setError(getString(R.string.error_invalid_email));
        focusView = mEmailView;
        cancel = true;
    }

    if (cancel) {
        focusView.requestFocus();
    } else {
        mLoginStatusMessageView.setText(R.string.login_progress_signing_in);
        showProgress(true);
        gAuth = new GoogleAuthentication(ctx, mEmailView.getText().toString());
        gAuth.setUserConfirmedListener(SettingsUnlockActivity.this);

        Bundle b = new Bundle();
        b.putString(AccountManager.KEY_PASSWORD, mPasswordView.getText().toString());
        try {
            gAuth.verifyAuth(b);
        } catch (IllegalArgumentException e) {
            doUnSuccessfulLogin();
        }
    }
}