Using this sendQKCToken function you can send ethereum from one walletAddress to another walletAddress:

wallet_addressStringEther wallet address
wallet_passwordStringThe password which you set up already for your wallet.
gas_priceBigIntegerThe price of gas for this transaction fee.
gas_limitBigIntegerThe amount of gas to use for the transaction.
qkc_amountBigDecimalThe amount of QKC you wish to send to the destination address.
sender_wallet_addressStringThe address for the sending account quark wallet address (sender's address).
receiver_wallet_addressStringThe destination quark wallet address (receiver's address).
QKCManager qkcManager = QKCManager.getInstance();
String walletAddress = "{{wallet_address}}";
String password = "{{wallet_password}}";
BigInteger gasPrice = new BigInteger("{{gas_price}}");
BigInteger gasLimit = new BigInteger("{{gas_limit}}");
BigDecimal qkcAmount = new BigDecimal("{{qkc_amount}}");
String fromAddress = "{{sender_wallet_address}}";
String receiverAddress = "{{receiver_wallet_address}}";
qkcManager.sendQKCToken(walletAddress, password, fromAddress, receiverAddress,gasPrice, gasLimit, qkcAmount, this)
                .subscribe(tx -> {

                    Toast.makeText(this, "TX : " + tx, Toast.LENGTH_SHORT).show();

                }, error -> {