Android以太坊智能合约交互

contract greeter is mortal {
    /* define variable greeting of the type string */
    string greeting;

    /* this runs when the contract is executed */
    function greeter(string _greeting) public {
        greeting = _greeting;
    }

    /* change greeting */
    function changeGreeting(string _greeting) public {
        greeting = _greeting;
    }

    /* main function */
    function greet() constant returns (string) {
        return greeting;
    }
}

solc greeter.sol --bin --abi --optimize -o <output-dir>/

web3j solidity generate /path/to/<smart-contract>.bin /path/to/<smart-contract>.abi -o /path/to/src/main/java -p com.your.organisation.name

InfuraHttpService infuraHttpService = new InfuraHttpService(url);
Web3j web3j = Web3jFactory.build("https://ropsten.infura.io/YOUR_API_KEY");

Greeter greeter = Greeter.load(greeterContractAddress, web3j, credentials, gasPrice, gasLimit);
Future<Utf8String> greeting = greeter.greet();
Utf8String greetingUtf8 = greeting.get();
String result = greetingUtf8.getValue();

Greeter greeter = Greeter.load(greeterContractAddress, web3j, credentials, gasPrice, gasLimit);
TransactionReceipt transactionReceipt = greeter.changeGreeting(new Utf8String(greetingToWrite)).get(timeout);
String result = "Successful transaction. Gas used: " + transactionReceipt.getGasUsed();