The Screen freezes, when executing a function in Flutter

Question

I am trying to build a wallet app and implementing a key generation function. When I click the button, I want the function to generate a key. However, the screen freezes until the function finishes.

import 'package:flutter/material.dart';
import 'package:web3dart/crypto.dart';
import 'package:web3dart/web3dart.dart';
import 'package:bip39/bip39.dart' as bip39;
import 'package:bip32/bip32.dart' as bip32;

class TestPage extends StatefulWidget {
  const TestPage({super.key});

  @override
  State<TestPage> createState() => _TestPageState();
}

class _TestPageState extends State<TestPage> {
  bool _isLoading = false;

  @override
  Widget build(BuildContext context) {
    return _isLoading
        ? const Center(child: CircularProgressIndicator())
        : Scaffold(
            body: Center(
              child: ElevatedButton(
                  onPressed: () async {
                    setState(() => _isLoading = true);
                    Credentials myCredentials = await _generateKeys();
                    print(myCredentials.address);
                    setState(() => _isLoading = false);
                  },
                  child: const Text('Generate credentials')),
            ),
          );
  }

  _generateKeys() {
    String mnemonic = generateMnemonic();
    return generateKeysFromMnemonic(mnemonic);
  }

  Credentials generateKeysFromMnemonic(String mnemonic) {
    final seed = bip39.mnemonicToSeed(mnemonic); // when this part runs, the screen freezes. T.T
    final masterNode = bip32.BIP32.fromSeed(seed);
    final bytesList = masterNode.privateKey;
    final String privateKey = bytesToHex(bytesList!);
    final Credentials credentials = EthPrivateKey.fromHex(privateKey);
    return credentials;
  }

  String generateMnemonic() {
    return bip39.generateMnemonic();
  }
}

When I execute this function(generateKeysFromMnemonic), the screen freezes.

I tried using async/await, but it didn't work well...

Please help me. how can I prevent the screen from freezing?

I want the function to execute when the button is pressed, without freezing the screen until the result is returned.