Ethereum,bscsartchain sign not reponse

[ylj318]

bnb expert:
it's question in android simulate from demo (https://github.com/trustwallet/wallet-core/tree/master/samples/android) ,invoke
AnySigner.sign(signerInput, CoinType.ETHEREUM, SigningOutput.parser()) method but return nothing ,right or wrong no response
code:
Ethereum.Transaction.Builder transaction = Transaction.newBuilder();
Ethereum.Transaction.Transfer.Builder transfer = Ethereum.Transaction.Transfer.newBuilder();
String signData = "0xa9059cbb0000000000000000000000000c5dBa0A59776c3C31c31ac1C19AaFAeb800d1E80000000000000000000000000000000000000000000000000de0b6b3a7640000";
transfer.setData(ByteString.copyFrom(signData.getBytes()));
transaction.setTransfer(transfer);
SigningInput signerInput = SigningInput.newBuilder()
.setChainId(ByteString.copyFrom(new BigInteger("01").toByteArray()))
.setPrivateKey(ByteString.copyFrom(privateKey.getBytes()))
.setGasPrice(ByteString.copyFrom(new BigInteger("d693a400",16).toByteArray())) //$0.gasPrice = Data(hexString: "d693a400")! // decimal 3600000000
.setGasLimit(ByteString.copyFrom(new BigInteger("5208",16).toByteArray()))
.setNonce(ByteString.copyFrom(new BigInteger("1").toByteArray()))
.setToAddress(contract address)
.setTransaction(transaction)
.build();
SigningOutput signingOutput = AnySigner.sign(signerInput, CoinType.ETHEREUM, SigningOutput.parser());

the content of signingOutput  is empty