波场区块链浏览器：https://tronscan.org/#/

API：https://cn.developers.tron.network/reference#reference-getting-started
Github上的API：https://github.com/tronscan/tronscan-frontend/blob/dev2019/document/api.md

针对Trx的离线签名（TransferContract）， trc10和trc20根据Protoc协议中构造Transaction中的TransferAssetContract和TriggerSmartContract签名即可

代码直接在官方钱包wallet-cli项目中写的demo

package org.tron.demo;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.google.protobuf.Any;
import com.google.protobuf.ByteString;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.tron.common.crypto.ECKey;
import org.tron.common.crypto.Sha256Hash;
import org.tron.common.utils.ByteArray;
import org.tron.common.utils.TransactionUtils;
import org.tron.protos.Contract;
import org.tron.walletserver.WalletApi;
import org.tron.protos.Protocol.Transaction;
import org.tron.protos.Protocol.BlockHeader;

/*
    author:hht
    email:593432577@qq.com
    des:Tron波场离线签名
 */
public class TronSignDemo {
    public static void main(String[] args) {
        String privateStr = "private key";
        byte[] privateByte = ByteArray.fromHexString(privateStr);
        ECKey ecKey = ECKey.fromPrivate(privateByte);
        byte[] from = ecKey.getAddress();
        byte[] to = WalletApi.decodeFromBase58Check("address");
        System.out.println("from::"+ByteArray.toHexString(from));
        System.out.println("to::"+ByteArray.toHexString(to));

        long amount = 321;
        Transaction transaction = createTransaction(from,to,amount);
        byte[] transactionBytes = transaction.toByteArray();
        System.out.println(ByteArray.toHexString(transactionBytes));
        Transaction transactionSign = TransactionUtils.sign(transaction,ecKey);
        System.out.println("transactionSign ::::: " + ByteArray.toHexString(transactionSign.toByteArray()));

        //g广播交易
        postBroadcast(ByteArray.toHexString(transactionSign.toByteArray()));
    }

    //构造交易 参考官网Protoc协议
    public static Transaction createTransaction(byte[] from,byte[] to,long amount){
        Transaction.Builder transactionBuilder = Transaction.newBuilder();

        Transaction.Contract.Builder contractBuilder = Transaction.Contract.newBuilder();

        Contract.TransferContract.Builder transferContractBuidler = Contract.TransferContract.newBuilder();
        transferContractBuidler.setOwnerAddress(ByteString.copyFrom(from));
        transferContractBuidler.setToAddress(ByteString.copyFrom(to));
        transferContractBuidler.setAmount(amount);

        Any any = Any.pack(transferContractBuidler.build());
        contractBuilder.setParameter(any);
        contractBuilder.setType(Transaction.Contract.ContractType.TransferContract);

        transactionBuilder.getRawDataBuilder().addContract(contractBuilder)
                .setTimestamp(System.currentTimeMillis())
                .setExpiration(System.currentTimeMillis()+10*60*60*1000);

        BlockHeader.raw raw = getNowBlock();
        byte[] blockHash = Sha256Hash.of(raw.toByteArray()).getBytes();
        byte[] blockNum = ByteArray.fromLong(raw.getNumber());
        System.out.println("block::::"+ByteArray.toHexString(blockHash));
        transactionBuilder.getRawDataBuilder()
                .setRefBlockHash(ByteString.copyFrom(ByteArray.subArray(blockHash,8,16)))
                .setRefBlockBytes(ByteString.copyFrom(ByteArray.subArray(blockNum,6,8)));

        return transactionBuilder.build();
    }


    public static BlockHeader.raw getNowBlock(){
        //使用RPC接口获取BlockHeader
//        Protocol.Block newestBlock = WalletApi.getBlock(-1);
//        return newestBlock.getBlockHeader().getRawData();

        //使用get请求获取blockHeader 目前只找到这个这个接口
        //https://apilist.tronscan.org/api/block/latest 这个接口获取的数据 少个version参数，打包广播的时候会出现 TAPOS_ERROR
        String nowBlockStr = getHttp("https://api.trongrid.io/wallet/getnowblock");
        JSONObject jsonObject = JSON.parseObject(nowBlockStr);
        String block_header = jsonObject.getString("block_header");
        JSONObject raw_data = JSON.parseObject(block_header);
        JSONObject data = JSON.parseObject(raw_data.getString("raw_data"));

        BlockHeader.raw.Builder rawBuidler = BlockHeader.raw.newBuilder();

        rawBuidler.setNumber(data.getLong("number"));
        rawBuidler.setTxTrieRoot(ByteString.copyFrom(ByteArray.fromHexString(data.getString("txTrieRoot"))));
        rawBuidler.setWitnessAddress(ByteString.copyFrom(ByteArray.fromHexString(data.getString("witness_address"))));
        rawBuidler.setParentHash(ByteString.copyFrom(ByteArray.fromHexString(data.getString("parentHash"))));
        rawBuidler.setTimestamp(data.getLong("timestamp"));
        rawBuidler.setVersion(data.getIntValue("version"));
        return rawBuidler.build();
    }

    public static String getHttp(String url) {
        try {
            HttpGet get = new HttpGet((url));
            HttpClient client = HttpClients.createDefault();
            HttpResponse response = client.execute(get);
            HttpEntity entity = response.getEntity();
            String result = EntityUtils.toString(entity);
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";
    }

    public static String postBroadcast(String sgin){
        try {
            //广播地址：https://apilist.tronscan.org/api/broadcast
            HttpPost post = new HttpPost("https://apilist.tronscan.org/api/broadcast");
            post.setEntity(new StringEntity("{\"transaction\":\""+sgin+"\"}"));
            HttpClient client = HttpClients.createDefault();
            HttpResponse response = client.execute(post);
            HttpEntity entity = response.getEntity();
            String result = EntityUtils.toString(entity);
            System.out.println(result);
            return result;
        }catch (Exception e){
            e.printStackTrace();
        }
        return "";
    }
}