区块链钱包开发(Android篇)

简介

本文主要内容为区块链钱包移动端(Android)开发,介绍比特币钱包和以太坊钱包的开发过程,包含钱包的主要功能:
创建钱包,钱包余额,导出钱包,钱包转账等。Demo地址

区块链钱包

在日常生活中,大家都会买个钱包用于存放政府机构发行的纸币,那么什么是数字资产世界的钱包呢?

比特币钱包

以太坊钱包:Mist、Parity、MyEhterWallet、ImToken、MetaTask、Ledger(硬件钱包)

  • 助记词等价于私钥
  • Keystore + 密码 等价于私钥

EOS钱包

NEO钱包

量子钱包

  • On-chain

    给一个钱包地址发送数字货币, 这笔交易在全网广播、被确认、被打包进区块。这是发生在链上的,被称为on-chain交易。on-chain钱包需要自己保管私钥。

  • Off-chain

    相对于on-chain交易是off-chain交易。通常,通过交易所进行的交易是off-chain的,本人并没有私钥。私钥在交易所,由交易所托管。所以交易所的钱包也是中心化的钱包。

  • 冷钱包

    冷即离线、断网,也就是说私钥存储的位置不能被网络所访问。例如纸钱包、脑钱包、硬件钱包等等。

  • 热钱包

    热即联网,也就是私钥存储在能被网络访问的位置。 例如存放在交易所的、在线钱包网站、手机App钱包都属于热钱包。通常而言,冷钱包更加安全,热钱包使用更加方便。

  • 非确定性钱包
    钱包随机生成

  • 确定性钱包(HD Wallets)
    同一个种子,能够派生一样的密钥对集合

  • 全节点钱包

    除了保存私钥外,全节点钱包还有保存了所有区块的数据,最为著名的是bitcoin-core。

  • 轻钱包

    它不必保存所有区块的数据,只保存跟自己相关的数据。基本可以实现去中心化。

  • 中心化钱包

    在交易所中的钱包,以及类似 OKLink 提供的保险柜服务。

比特币钱包

https://bitcoin.org/en/developer-guide#wallets

  • 比特币钱包的组成
  • 比特币钱包地址的创建过程
  • BIP32
  • BIP39
  • BIP43
  • BIP44
  • BitcoinJ创建钱包
  • Bitcoin钱包收款和转账

比特币钱包组成

比特币钱包分为两部分:钱包程序和钱包文件

钱包文件

保存私钥和转账记录

Wallet containing 0.01 BTC (spendable: 0.01 BTC) in:
  0 pending transactions
  1 unspent transactions
  0 spent transactions
  0 dead transactions
Last seen best block: 1384907 (2018-08-22T03:38:42Z): 0000000000000030fe01a48a7cd6b0c52909a7d019084d195ae3ebd2889c82ec

Keys:
Earliest creation time: 2018-08-20T07:51:29Z
Seed birthday: 1534751489  [2018-08-20T07:51:29Z]
Key to watch:  tpubD92y4mcSrbcSxANfCgiWx7h7sGquSF4ogNPcUxC2GECSwgWBMNPMo2C8nxez2ngvSS4UfaGhSunemWoqZ6aAAzLb4WLsmQxDirfFgE9tG5J
  addr:mq5gdvJDuDEmNKFPbgMn8pGm3pyJvkSsHv  hash160:68e9c9e06890527cd0f0b59d83333502ac127bef  (M/0H/0/0)


>>> UNSPENT:
0.01 BTC total value (sends 0.00 BTC and receives 0.01 BTC)
  confidence: Seen by 7 peers (most recently: 2018-08-22T03:33:33Z). Appeared in best chain at height 1384907, depth 1. Source: NETWORK
  a82c35c2133bd357bfa462f82d75b28787afcdcd20c8b89cd2b78f48138d6e9f
  updated: 2018-08-22T03:31:53Z
     in   PUSHDATA(71)[304402205d3e0974b4604b92e09f83950b183100bd47243c9cb548f2213a9ca26e83bdd3022018278c7ce9b65982e6c67ba9acf8e6e3898f1dad80702bb1e32c4a0b61195e0f01] PUSHDATA(33)[02f8769ecddd821cc9b75c554978b4a674df28c098e640fd0188b88bf019bc31fa]
          outpoint:8294b8dcf6513ab13321d4dd1642bf1c19600a313bf1ebe8511521dcd4dd0277:0
     out  DUP HASH160 PUSHDATA(20)[8843beff2291c5a00aa00fbd8a541f800c83b86d] EQUALVERIFY CHECKSIG 1.1899548 BTC
     out  DUP HASH160 PUSHDATA(20)[68e9c9e06890527cd0f0b59d83333502ac127bef] EQUALVERIFY CHECKSIG 0.01 BTC
     prps UNKNOWN
     ##  ##

钱包程序

钱包程序,创建公钥来接受satoshi,使用私钥来使用satoshi。钱包程序可以拆分出3个独立的模块:公钥分发模块、签名模块、网络模块

 比特币单位:
 1比特币(Bitcoins,BTC)  
 0.01比特分(Bitcent,cBTC)
 0.001毫比特(Milli-Bitcoins,mBTC)
 0.000001微比特(Micro-Bitcoins,μBTC或uBTC) 
 0.00000001聪(satoshi)(基本单位) 
 1 bitcoin (BTC) = 1000 millibitcoins (mBTC) = 1 million microbitcoins (uBTC) = 100 million Satoshi  

根据三个模块的组合,可以分为全服务钱包、只签名钱包(离线钱包和硬件钱包)、只分发钱包。

BIP协议

Bitcoin Improvement Proposals

BIP32

BIP32:定义了层级确定性钱包(hierarchical deterministic wallets),是一个系统可以从单一个 seed 产生一树状结构储存多组 keypairs(私钥和公钥)。好处是可以方便的备份、转移到其他相容装置(因为都只需要 seed),以及分层的权限控制等。

作用:

  • 1、备份更容易。按照比特币的原则,尽量不要使用同一个地址,一个地址只使用一次,这样会导致频繁备份钱包。HD钱包只需要在创建时保存主密钥,通过主密钥可以派生出所有的子密钥。

  • 2、私钥离线更安全。主私钥离线存储,主公钥在线使用,通过主公钥可以派生出所有的子公钥。例如:给每个商品提供一个收款地址。

  • 3、利于管理,权限控制。树状结构类似于公司的组织架构,可以给各个部门指定一个密钥分支。

  • 4、记账。只使用公钥即可记账。

BIP39

BIP39:将seed 用方便记忆和书写的单字表示。一般由 12 个单字组成,称为 mnemonic code(phrase),中文称为助记词或助记码。例如:
average green proud remember advance trick estate oblige trouble when cube person

Wordlists

工具

BIP43

BIP43

BIP43对BIP32树结构增加了子索引标识purpose的拓展m/purpose’/*

BIP32的索引:m/0’/*

BIP44的索引:m/44’/*。

BIP44

BIP44:基于BIP32和BIP43,赋予树状结构中的各层特殊的意义。让同一个 seed 可以支援多币种、多帐户等。各层定义如下:

m / purpose' / coin_type' / account' / change / address_index
  • purporse’: 固定值44’, 代表是BIP44
  • coin_type’: 这个代表的是币种, 可以兼容很多种币, 比如BTC是0’, ETH是60’, 例如:btc一般是 m/44’/0’/0’/0, eth一般是 m/44’/60’/0’/0
  • account’:账号
  • change’: 0表示外部链(External Chain),用户接收比特币,1表示内部链(Internal Chain),用于接收找零
  • address_index:钱包索引

钱包最佳实践

  • 使用助记词(BIP39)
  • 使用层级确定性钱包(HD Wallets)(BIP32)
  • 使用多目的HD Wallets(BIP43)
  • 使用多币种,多账号的HD Wallets (BIP44)

比特币钱包地址创建过程

1、生成128bit~256bit作为私钥

2、通过secp256k1椭圆曲线算法得到私钥对应的公钥

3、将公钥进行SHA-256,得到公钥Hash

4、将3的结果进行RIMEMD-160

5、将4中结果添加1个字节版本号

6、将5中结果进行两次SHA-256,取前4个字节作为checksum

7、将6中结果添加到5中结果的末尾

8、将7中结果进行Base58,结果为比特币地址

BitcoinJ创建钱包

Bitcoinj是比特币协议Java版本实现的库。

添加依赖:

dependencies {
    implementation 'org.bitcoinj:bitcoinj-core:0.14.7'
    implementation 'org.slf4j:slf4j-api:1.7.25'
    implementation 'com.squareup.okhttp3:okhttp:3.10.0'
    implementation 'com.squareup.okhttp3:logging-interceptor:3.10.0'
    implementation 'com.google.zxing:core:3.3.3'//二维码
}

Android最大方法数的限制,60K
开启multiDexEnabled

android {
    compileSdkVersion 28
    defaultConfig {
        multiDexEnabled true
    }
}

dependencies {
    implementation 'com.android.support:multidex:1.0.3'
}

创建新钱包

File walletFile = activity.getFileStreamPath("wallet-protobuf");
//创建钱包
wallet = new Wallet(Constants.NETWORK_PARAMETERS);
//创建WalletFiles,设置自动保存Wallet
WalletFiles walletFiles = wallet.autosaveToFile(walletFile, 3 * 1000, TimeUnit.MILLISECONDS, null);
//立即保存
walletFiles.saveNow();

钱包创建源码分析:

  • Wallet

  • KeyChainGroup

  • DeterministicKeyChain

  • DeterministicSeed

      protected DeterministicKeyChain(DeterministicSeed seed, @Nullable KeyCrypter crypter) {
          this.seed = seed;
          basicKeyChain = new BasicKeyChain(crypter);
          if (!seed.isEncrypted()) {
              rootKey = HDKeyDerivation.createMasterPrivateKey(checkNotNull(seed.getSeedBytes()));
              rootKey.setCreationTimeSeconds(seed.getCreationTimeSeconds());
              addToBasicChain(rootKey);
              hierarchy = new DeterministicHierarchy(rootKey);
              for (int i = 1; i <= getAccountPath().size(); i++) {
                  addToBasicChain(hierarchy.get(getAccountPath().subList(0, i), false, true));
              }
              initializeHierarchyUnencrypted(rootKey);
          }
          // Else...
          // We can't initialize ourselves with just an encrypted seed, so we expected deserialization code to do the
          // rest of the setup (loading the root key).
      }
    

获取钱包地址

Address address = wallet.currentAddress(KeyChain.KeyPurpose.RECEIVE_FUNDS);
address.toString();

在获取地址的过程中会调用RIMEMD-160算法处理公钥hash:

//Utils.java
public static byte[] sha256hash160(byte[] input) {
    byte[] sha256 = Sha256Hash.hash(input);
    RIPEMD160Digest digest = new RIPEMD160Digest();
    digest.update(sha256, 0, sha256.length);
    byte[] out = new byte[20];
    digest.doFinal(out, 0);
    return out;
}

处理公钥hash后会进行Base58算法:

//VersionedChecksummedBytes.java
public final String toBase58() {
    // A stringified buffer is:
    //   1 byte version + data bytes + 4 bytes check code (a truncated hash)
    byte[] addressBytes = new byte[1 + bytes.length + 4];
    addressBytes[0] = (byte) version;
    System.arraycopy(bytes, 0, addressBytes, 1, bytes.length);
    byte[] checksum = Sha256Hash.hashTwice(addressBytes, 0, bytes.length + 1);
    System.arraycopy(checksum, 0, addressBytes, bytes.length + 1, 4);
    return Base58.encode(addressBytes);
}

从文件中加载钱包

//读取钱包文件
File walletFile = activity.getFileStreamPath("wallet-protobuf");
if (walletFile.exists()) {
    InputStream inputStream = new FileInputStream(walletFile);
    //反序列化
    wallet  = new WalletProtobufSerializer().readWallet(inputStream);
    //设置自动保存
    wallet.autosaveToFile(walletFile, 3 * 1000, TimeUnit.MILLISECONDS, null);
    //清理钱包
    wallet.cleanup();
} 

创建地址二维码

String s = BitcoinURI.convertToBitcoinURI(address, null, null, null);
Bitmap bitmap = Qr.bitmap(s);
BitmapDrawable bitmapDrawable = new BitmapDrawable(getResources(), bitmap);
bitmapDrawable.setFilterBitmap(false);
mQrImageView.setImageDrawable(bitmapDrawable);

public static Bitmap bitmap(final String content) {
    try {
        final Hashtable hints = new Hashtable();
        hints.put(EncodeHintType.MARGIN, 0);
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H);
        final BitMatrix result = QR_CODE_WRITER.encode(content, BarcodeFormat.QR_CODE, 0, 0, hints);

        final int width = result.getWidth();
        final int height = result.getHeight();
        final byte[] pixels = new byte[width * height];

        for (int y = 0; y < height; y++) {
            final int offset = y * width;
            for (int x = 0; x < width; x++) {
                pixels[offset + x] = (byte) (result.get(x, y) ? -1 : 0);
            }
        }

        final Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);
        bitmap.copyPixelsFromBuffer(ByteBuffer.wrap(pixels));
        return bitmap;
    } catch (final WriterException x) {
        log.info("problem creating qr code", x);
        return null;
    }
}

Bitcoin钱包收款和转账

比特币钱包余额需要统计所有钱包地址对应的UTXO

Simplified Payment Verification (SPV):节点无需下载所有的区块数据,而只需要加载所有区块头数据(block header的大小为80B),即可验证这笔交易是否曾经被比特币网络认证过。

布隆过滤器(Bloom Filter):过滤掉那些不包含有目标地址的交易信息,这一步能避免掉大量不相关的数据下载。

创建区块链

//创建区块链文件
File blockChainFile = new File(getDir("blockstore", Context.MODE_PRIVATE), "blockchain");
//创建SPVBlockStore,管理区块数据
blockStore = new SPVBlockStore(Constants.NETWORK_PARAMETERS, blockChainFile);
//加载检查点
final InputStream checkpointsInputStream = getAssets().open("checkpoints-testnet.txt");
CheckpointManager.checkpoint(Constants.NETWORK_PARAMETERS, checkpointsInputStream,
                        blockStore, earliestKeyCreationTime);
//创建区块链对象
blockChain = new BlockChain(Constants.NETWORK_PARAMETERS, wallet, blockStore);

同步区块链

//添加网络权限:


private void startup() {
    Log.d(TAG, "startup: ");
    peerGroup = new PeerGroup(Constants.NETWORK_PARAMETERS, blockChain);
    peerGroup.setDownloadTxDependencies(0); // recursive implementation causes StackOverflowError
    peerGroup.addWallet(wallet);//设置钱包,重要
    try {
        PackageInfo packageInfo = getPackageManager().getPackageInfo(getPackageName(), PackageManager.GET_ACTIVITIES);
        peerGroup.setUserAgent(USER_AGENT, packageInfo.versionName);
    } catch (PackageManager.NameNotFoundException e) {
        e.printStackTrace();
    }
    peerGroup.setMaxConnections(8);
    int connectTimeout = (int) (15 * DateUtils.SECOND_IN_MILLIS);
    peerGroup.setConnectTimeoutMillis(connectTimeout);
    int discoveryTimeout = (int) (10 * DateUtils.SECOND_IN_MILLIS);
    peerGroup.addConnectedEventListener(mPeerConnectedEventListener);
    peerGroup.addDisconnectedEventListener(mPeerDisconnectedEventListener);
    peerGroup.addDiscoveredEventListener(mPeerDiscoveredEventListener);
    peerGroup.setPeerDiscoveryTimeoutMillis(discoveryTimeout);

	//添加节点探索器,重要
    peerGroup.addPeerDiscovery(new PeerDiscovery() {
        private final PeerDiscovery normalPeerDiscovery = MultiplexingDiscovery
                .forServices(Constants.NETWORK_PARAMETERS, 0);

        @Override
        public InetSocketAddress[] getPeers(final long services, final long timeoutValue,
                                            final TimeUnit timeoutUnit) throws PeerDiscoveryException {
            return normalPeerDiscovery.getPeers(services, timeoutValue, timeoutUnit);
        }

        @Override
        public void shutdown() {
            normalPeerDiscovery.shutdown();
        }
    });
    peerGroup.startAsync();
    peerGroup.startBlockChainDownload(null);
}

比特币收款

获取测试用比特币:https://testnet.manu.backend.hamburg/faucet
刚收到的币可能需要几分钟后才能使用

//监听比特币接受事件
wallet.addCoinsReceivedEventListener(mWalletListener);
//刷新余额
Coin balance = wallet.getBalance(Wallet.BalanceType.ESTIMATED);

比特币转账

比特币测试链转账查询
创建一个Tx,对Tx进行签名,对Tx进行P2P网络广播

Address address = Address.fromBase58(Constants.NETWORK_PARAMETERS, to);	
//转账金额,以mBTC为单位
Coin coin = MonetaryFormat.MBTC.parse(amount);
//创建请求
SendRequest sendRequest = SendRequest.to(address, coin);
try {
    //创建Transaction
    Transaction transaction = wallet.sendCoinsOffline(sendRequest);
    //通过P2P广播
    BlockChainService.broadcastTransaction(BitcoinWalletActivity.this, transaction);
} catch (InsufficientMoneyException e) {
    Toast.makeText(this, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show();
    e.printStackTrace();
}

public static void broadcastTransaction(Context context, Transaction transaction) {
    Intent intent = new Intent(ACTION_BROADCAST_TRANSACTION, null, context, BlockChainService.class);
    intent.putExtra(ACTION_BROADCAST_TRANSACTION_HASH, transaction.getHash().getBytes());
    context.startService(intent);
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Log.d(TAG, "onStartCommand: ");
    if (intent != null) {
        byte[] txHash = intent.getByteArrayExtra("tx");
        if (txHash != null) {
            Sha256Hash sha256Hash = Sha256Hash.wrap(txHash);
            Transaction transaction = BitcoinWalletManager.getInstance().getWallet().getTransaction(sha256Hash);
            peerGroup.broadcastTransaction(transaction);
            Log.d(TAG, "onStartCommand: " + sha256Hash.toString());
        }
    }
    return super.onStartCommand(intent, flags, startId);
}

以太坊钱包

https://github.com/ethereumbook/ethereumbook/blob/develop/wallets.asciidoc

以太坊钱包功能与比特币钱包功能类似,获取用户余额,管理地址和密钥,转账、智能合约调用。以太坊钱包一般不用在本地维护区块链数据,只需要使用JSON-RPC访问

钱包文件

KeyStore = 私钥 + 密码

如果使用ImToken创建钱包,创建了助记词,密码用来加密钱包地址对应的子私钥,加密的结果就是Keystore.

{
    "address": "001d3f1ef827552ae1114027bd3ecf1f086ba0f9",
    "crypto": {
        "cipher": "aes-128-ctr",
        "ciphertext": "233a9f4d236ed0c13394b504b6da5df02587c8bf1ad8946f6f2b58f055507ece",
        "cipherparams": {
            "iv": "d10c6ec5bae81b6cb9144de81037fa15"
        },
        "kdf": "scrypt",
        "kdfparams": {
            "dklen": 32,
            "n": 262144,
            "p": 1,
            "r": 8,
            "salt": "99d37a47c7c9429c66976f643f386a61b78b97f3246adca89abe4245d2788407"
        },
        "mac": "594c8df1c8ee0ded8255a50caf07e8c12061fd859f4b7c76ab704b17c957e842"
    },
    "id": "4fcb2ba4-ccdb-424f-89d5-26cce304bf9c",
    "version": 3
}

以太坊钱包地址创建过程

1、使用Secp256k1创建公私钥

2、通过Keccak算法得到公钥Hash值,进而得到长度为40的地址字符串

3、一般的,会在地址字符串签名加前缀"0x"

Web3j创建钱包

Web3j

添加Web3j依赖

implementation 'org.web3j:core:3.3.1-android'

创建新钱包

这里不涉及BIP协议,为非确定性钱包

Wallet.createStandard() 出现OOM, Out of Memory
https://juejin.im/post/5b4b07f8e51d45199060fe1f

File walletDir = contextWrapper.getDir("eth", Context.MODE_PRIVATE);
//生成密钥对
ECKeyPair ecKeyPair = Keys.createEcKeyPair();
//WalletFile = KeyStore
WalletFile wallet = Wallet.createLight(PASSWORD, ecKeyPair);
String walletFileName = getWalletFileName(wallet);
File destination = new File(walletDir, walletFileName);
objectMapper.writeValue(destination, wallet);

加载钱包文件

File[] files = walletDir.listFiles();
wallet = objectMapper.readValue(files[0], WalletFile.class);

通过助记词创建钱包

涉及BIP协议,但没有遵循bitcoin地址只使用一次的原则,钱包一般只使用派生出来第一个地址

可通过工具检查派生的地址是否正确

//创建助记词
public List createMnemonics() throws MnemonicException.MnemonicLengthException {
    SecureRandom secureRandom = new SecureRandom();
    byte[] entropy = new byte[DeterministicSeed.DEFAULT_SEED_ENTROPY_BITS / 8];
    secureRandom.nextBytes(entropy);
    return  MnemonicCode.INSTANCE.toMnemonic(entropy);
}

//m / 44' / 60' / 0' / 0
//Hardened意思就是派生加固,防止获取到一个子私钥之后可以派生出后面的子私钥
//必须还有上一级的父私钥才能派生
public static final ImmutableList BIP44_ETH_ACCOUNT_ZERO_PATH =
        ImmutableList.of(new ChildNumber(44, true), new ChildNumber(60, true),
                ChildNumber.ZERO_HARDENED, ChildNumber.ZERO);

//通过助记词生成HD钱包
public void onCreateWallet(View view) {

    byte[] seed = MnemonicCode.toSeed(words, "");
    DeterministicKey masterPrivateKey = HDKeyDerivation.createMasterPrivateKey(seed);
    DeterministicHierarchy deterministicHierarchy = new DeterministicHierarchy(masterPrivateKey);
    // m / 44' / 60' / 0' / 0 / 0
    DeterministicKey deterministicKey = deterministicHierarchy
            .deriveChild(BIP44_ETH_ACCOUNT_ZERO_PATH, false, true, new ChildNumber(0));
    byte[] bytes = deterministicKey.getPrivKeyBytes();
    ECKeyPair keyPair = ECKeyPair.create(bytes);
    try {
        WalletFile walletFile = Wallet.createLight(PASSWORD, keyPair);
        String address = walletFile.getAddress();
        mAddress.setText("0x" + address);
    } catch (CipherException e) {
        e.printStackTrace();
    }
}

导出钱包

导出KeyStore

public String exportKeyStore(WalletFile wallet) {
    try {
        return objectMapper.writeValueAsString(wallet);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    }
    return null;
}

导出私钥

public String exportPrivateKey(WalletFile wallet) {
    try {
        ECKeyPair ecKeyPair = Wallet.decrypt(PASSWORD, wallet);
        BigInteger privateKey = ecKeyPair.getPrivateKey();
        return  Numeric.toHexStringNoPrefixZeroPadded(privateKey, Keys.PRIVATE_KEY_LENGTH_IN_HEX);
    } catch (CipherException e) {
        e.printStackTrace();
    }
    return null;
}

导出助记词

一般可以将助记词加密存储,导出时解密。注意无法从KeyStore或者私钥导出助记词。

例如:使用IMToken导入私钥或者KeyStore创建的钱包,没有导出助记词的功能
如果是通过助记词创建的,就会有导出助记词的功能

ETH交易

获取Robsten测试网络ETH

查询余额

private Web3j mWeb3j = Web3jFactory.build(new HttpService("https://ropsten.infura.io/1UoO4I/"));
BigInteger balance = mWeb3j.ethGetBalance(mAddress, DefaultBlockParameterName.LATEST).send().getBalance();
BigDecimal balance = Convert.fromWei(balance.toString(), Convert.Unit.ETHER);

ETH转账

转账记录查询

BigInteger transactionCount = mWeb3j.ethGetTransactionCount(mAddress, DefaultBlockParameterName.LATEST).send().getTransactionCount();
BigInteger gasPrice = mWeb3j.ethGasPrice().send().getGasPrice();
BigInteger gasLimit = new BigInteger("200000");
BigDecimal value = Convert.toWei(mAmountEdit.getText().toString().trim(), Convert.Unit.ETHER);
String to = mToAddressEdit.getText().toString().trim();
RawTransaction etherTransaction = RawTransaction.createEtherTransaction(transactionCount, gasPrice, gasLimit, to, value.toBigInteger());
ECKeyPair ecKeyPair = Wallet.decrypt("a12345678", mWalletFile);
Credentials credentials = Credentials.create(ecKeyPair);
byte[] bytes = TransactionEncoder.signMessage(etherTransaction, credentials);
String hexValue = Numeric.toHexString(bytes);
String transactionHash = mWeb3j.ethSendRawTransaction(hexValue).send().getTransactionHash();

Token交易

获取某Token余额

调用ERC20代币智能合约,获取当前地址的余额

//创建Function
private Function balanceOf(String owner) {
    return new Function("balanceOf",
            Collections.singletonList(new Address(owner)),
            Collections.singletonList(new TypeReference(){}));
}

Function function = balanceOf(mAddress);
//调用智能合约
String s = callSmartContractFunction(function, CONTRACT_ADDRESS);
List decode = FunctionReturnDecoder.decode(s, function.getOutputParameters());
if (decode != null && decode.size() > 0) {
    Uint256 type = (Uint256) decode.get(0);
    BigInteger tokenBalance = type.getValue();
}

private String callSmartContractFunction(
        Function function, String contractAddress) throws Exception {
    String encodedFunction = FunctionEncoder.encode(function);

    org.web3j.protocol.core.methods.response.EthCall response = mWeb3j.ethCall(
            Transaction.createEthCallTransaction(
                    mAddress, contractAddress, encodedFunction),
            DefaultBlockParameterName.LATEST)
            .sendAsync().get();

    return response.getValue();
}

Token转账

//创建Function
private Function transfer(String to, BigInteger value) {
    return new Function(
            "transfer",
            Arrays.asList(new Address(to), new Uint256(value)),
            Collections.singletonList(new TypeReference() {}));
}

Function transfer = transfer(to, new BigInteger(amount));
//获取私钥,进行签名
ECKeyPair ecKeyPair = Wallet.decrypt("a12345678", mWalletFile);
Credentials credentials = Credentials.create(ecKeyPair);
String transactionHash = execute(credentials, transfer, CONTRACT_ADDRESS);

//执行合约调用
private String execute(
        Credentials credentials, Function function, String contractAddress) throws Exception {
    BigInteger nonce =  mWeb3j.ethGetTransactionCount(mAddress, DefaultBlockParameterName.LATEST).send().getTransactionCount();
    BigInteger gasPrice = mWeb3j.ethGasPrice().send().getGasPrice();
    BigInteger gasLimit = new BigInteger("200000");
    String encodedFunction = FunctionEncoder.encode(function);

    RawTransaction rawTransaction = RawTransaction.createTransaction(
            nonce,
            gasPrice,
            gasLimit,
            contractAddress,
            encodedFunction);

    byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
    String hexValue = Numeric.toHexString(signedMessage);

    EthSendTransaction transactionResponse = mWeb3j.ethSendRawTransaction(hexValue)
            .sendAsync().get();

    return transactionResponse.getTransactionHash();
}

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