Create a symmetric key inside the Android Keystore.

AesKeyGenerator.java

// Get the KeyGenerator instance for AES
KeyGenerator keyGenerator = KeyGenerator.getInstance(
    KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");

// Create a KeyGenParameterSpec builder and 
// set the alias and different purposes of the key
KeyGenParameterSpec.Builder builder = new KeyGenParameterSpec.Builder(
    "myAwesomeSecretKey01",
    KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT);

// The KeyGenParameterSpec is how parameters for your key are passed to the 
// generator. Choose wisely!
builder
    .setKeySize(256)
    .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_PKCS7);

// Generate and store the key
keyGenerator.init(builder.build());
keyGenerator.generateKey();

Where exactly is the key stored ? How can you get the key as a string or byte[] after all these steps ? Do you need to make all these steps everytime you open the app? or is there a condition you can set to only get the key insted of generating it again?