UniSwap 使用Web3j 生成原生币兑换代币。

val function =when(methodName){
        "swapEthForExactTokens" -> {
            val amountOut =map["amountOut"] as Int
            val address =Gson().fromJson<String>(map["address"] as JsonArray,object :TypeToken<List<String>>(){}.type).map { Address(it.toString()) }
            val toAddress =map["to"] as String
            val deadline =map["deadline"] as Int
            Function(  methodName, listOf(Uint(amountOut.toBigInteger()), DynamicArray(address), Address(toAddress), Uint(deadline.toBigInteger())),listOf(object : TypeReference<Type<*>?>() {}))
        }
        else ->Function(methodName, listOf(Address(approveToAddress), Uint256(num.toPlainString().toBigInteger())), listOf(object : TypeReference<Type<*>?>() {}))
    }

    //创建RawTransaction交易对象
    val rawTransaction = RawTransaction.createTransaction(nonce.toBigInteger(), gasPrice.toBigInteger(), gasLimit.toBigInteger(), contractAddress,  FunctionEncoder.encode(function))

    //签名Transaction
    val signMessage = TransactionEncoder.signMessage(rawTransaction,  Credentials.create(fromPrivateKey))
    return Numeric.toHexString(signMessage)