Store Private Keys in AndroidkeyStore using RSA encryption to decryt encrypted strings Android

Question

I have question i want to store my Keypairs using RSA encrption to encrypt my private credetials .i am using bellow code (Its is returning null when decrypting particular string by using there encrypted token(This happen when i reinstall my application)) .

 @TargetApi(Build.VERSION_CODES.M) static SecurityKey generateSecretKey(KeyStore keyStore) {
    try {
        Log.i("keyStore","is: "+keyStore);
        if (!keyStore.containsAlias(KEY_ALIAS)) {
            KeyGenerator keyGenerator =
                    KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEY_STORE);
            keyGenerator.init(new KeyGenParameterSpec.Builder(KEY_ALIAS,
                    KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT).setBlockModes(
                    KeyProperties.BLOCK_MODE_GCM)
                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
                    .setRandomizedEncryptionRequired(false)
                    .build());
            return new SecurityKey(keyGenerator.generateKey());
        }
    } catch (KeyStoreException | NoSuchProviderException | NoSuchAlgorithmException | InvalidAlgorithmParameterException e) {
        Timber.e(e);
    }
    try {
        final KeyStore.SecretKeyEntry entry =
                (KeyStore.SecretKeyEntry) keyStore.getEntry(KEY_ALIAS, null);
        return new SecurityKey(entry.getSecretKey());
    } catch (KeyStoreException | NoSuchAlgorithmException | UnrecoverableEntryException e) {
        Timber.e(e);
    }
    return null;
}