Developer Docs

Installation

To interact with the Ethereum blockchain, Magic Android SDK integrates Web3j as sub dependency. Add the following dependencies in build.gradle

Kotlin

dependencies {
  implementation 'link.magic:magic-android:4.0.0'
  implementation 'org.web3j:core:4.8.8-android'
  implementation 'org.web3j:geth:4.8.8-android'
}

Initialization

The Magic class is the entry-point to the Magic SDK. It must be instantiated with a Magic publishable key.

NoteThe following example uses Kotlin 1.3 and Magic Android 4.x. Android demo will be open-sourced soon. You may use Android Studio to convert Java to Kotlin or vice versa.

Kotlin

class MagicDemoApp: Application() {
  lateinit var magic: Magic
  override fun onCreate() {
    magic = Magic(this, "YOUR_PUBLISHABLE_KEY")
    super.onCreate()
  }
}

// Initialize web3j
class MagicActivity: AppCompatActivity() {
  lateinit var web3j: Web3j
  lateinit var gethWeb3j: Geth

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    web3j = Web3j.build(magic.rpcProvider)
    gethWeb3j = Geth.build(magic.rpcProvider)
  }
}

Use Different Networks

Testnet

Goerli Block Explorer: https://goerli.etherscan.io ⁠Goerli Testnet Faucet: https://goerlifaucet.com

Kotlin

magic = Magic(this, "YOUR_PUBLISHABLE_API_KEY", Magic.Network.goerli)

Custom Node

You can allow specific URLs to interact with the Magic SDK, such as a custom RPC URL to send transactions to your node. The Content Security Policy (CSP) of a browser dictates what resources can be loaded. You can update the policy in the settings page of the dashboard with your custom URL.

Important The use of a custom node will require the RPC URL to the project’s Content Security Policy from your Magic Dashboard. Refer to the CSP documentation.

Kotlin

magic = Magic(this, "YOUR_PUBLISHABLE_API_KEY", CustomNodeConfiguration("https://alchemy.io"))

Important Do not set the custom nodes to local IP address (E.x. http://127.0.0.1), because local IP will point to the network environment inside mobile device / simulator. Try accessible IP address in the same Wifi/Internet Environment (E.x. http://10.0.0.93:3000).

Associated Class

CustomNodeConfiguration(rpcUrl: String, chainId: Int?)

rpcUrl: Your own node URL
chainId: Your own node’s chainId

Magic.EthNetwork

Kotlin

enum class EthNetwork {
  Mainnet, Goerli
}

Common Methods

Send Transaction

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic
  lateinit var web3j: Web3j

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
    web3j = Web3j.build(magic.rpcProvider)
  }

  // After user is successfully authenticated
  fun sendTransaction(v: View) {
    try {
      val value: BigInteger =  Convert.toWei("0.5", Convert.Unit.ETHER).toBigInteger()
      val transaction = createEtherTransaction(account, BigInteger("1"), BigInteger("21000"), BigInteger("21000"), account, value)
      val receipt = web3j.ethSendTransaction(transaction).send()
      Log.d("Transaction complete: " + receipt.transactionHash)
    } catch (e: Exception) {
      Log.e("Error", e.localizedMessage)
    }
  }
}

Sign Message

Magic Android SDK extends the functionality from Web3j to allow developers to sign Typed Data. You may find it in magic.web3jSigExt.

Personal Sign

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic
  lateinit var web3j: Web3j
  lateinit var gethWeb3j: Geth

  // After user is successfully authenticated
  private var account: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
    web3j = Web3j.build(magic.rpcProvider)
    gethWeb3j = Geth.build(magic.rpcProvider)
  }

  fun personSign(view: View) {
    val message = "Hello from Magic!!!"
    val personalSign: PersonalSign = gethWeb3j.personalSign(
      message, account, "password")
      .send()
    Log.d("Magic", "Signed Message: " + personalSign.signedMessage)

    // Recover Message
    val recovered = gethWeb3j.personalEcRecover(message, personalSign.signedMessage).send()
    Log.d("Magic", "Recovered Address: " + recovered.recoverAccountId)
  }
}

Sign TypedData Legacy (V1)

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic

  // After user is successfully authenticated
  private var account: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
  }

  // Sign with EIP712 Data Field
  fun signTypedDataLegacy(v: View) {
    val list = listOf(
      EIP712TypedDataLegacyFields("string", "Hello from Magic", "This message will be signed by you"),
      EIP712TypedDataLegacyFields("uint32", "Here is a number", "90210")
    )
    val signature = magic.web3jSigExt.signTypedDataLegacy(account, list).send()
    Log.d("Magic", signature.result)
  }

  // Sign with JSON String
  fun signTypedDataLegacyJson(v: View) {
    val jsonString = "[{\"type\":\"string\",\"name\":\"Hello from Magic\",\"value\":\"This message will be signed by you\"},{\"type\":\"uint32\",\"name\":\"Here is a number\",\"value\":\"90210\"}]"
    val signature = magic.web3jSigExt.signTypedDataLegacy(account, jsonString).send()
    Log.d("Magic", signature.result)
  }
}

Sign Typed Data v3

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic
  lateinit var web3j: Web3j
  lateinit var gethWeb3j: Geth

  // After user is successfully authenticated
  private var account: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
  }

  fun signTypedData(v: View) {
    val jsonString = "{\"types\":{\"EIP712Domain\":[{\"name\":\"name\",\"type\":\"string\"},{\"name\":\"version\",\"type\":\"string\"},{\"name\":\"verifyingContract\",\"type\":\"address\"}],\"Order\":[{\"name\":\"makerAddress\",\"type\":\"address\"},{\"name\":\"takerAddress\",\"type\":\"address\"},{\"name\":\"feeRecipientAddress\",\"type\":\"address\"},{\"name\":\"senderAddress\",\"type\":\"address\"},{\"name\":\"makerAssetAmount\",\"type\":\"uint256\"},{\"name\":\"takerAssetAmount\",\"type\":\"uint256\"},{\"name\":\"makerFee\",\"type\":\"uint256\"},{\"name\":\"takerFee\",\"type\":\"uint256\"},{\"name\":\"expirationTimeSeconds\",\"type\":\"uint256\"},{\"name\":\"salt\",\"type\":\"uint256\"},{\"name\":\"makerAssetData\",\"type\":\"bytes\"},{\"name\":\"takerAssetData\",\"type\":\"bytes\"}]},\"domain\":{\"name\":\"0x Protocol\",\"version\":\"2\",\"verifyingContract\":\"0x35dd2932454449b14cee11a94d3674a936d5d7b2\"},\"message\":{\"exchangeAddress\":\"0x35dd2932454449b14cee11a94d3674a936d5d7b2\",\"senderAddress\":\"0x0000000000000000000000000000000000000000\",\"makerAddress\":\"0x338be8514c1397e8f3806054e088b2daf1071fcd\",\"takerAddress\":\"0x0000000000000000000000000000000000000000\",\"makerFee\":\"0\",\"takerFee\":\"0\",\"makerAssetAmount\":\"97500000000000\",\"takerAssetAmount\":\"15000000000000000\",\"makerAssetData\":\"0xf47261b0000000000000000000000000d0a1e359811322d97991e03f863a0c30c2cf029c\",\"takerAssetData\":\"0xf47261b00000000000000000000000006ff6c0ff1d68b964901f986d4c9fa3ac68346570\",\"salt\":\"1553722433685\",\"feeRecipientAddress\":\"0xa258b39954cef5cb142fd567a46cddb31a670124\",\"expirationTimeSeconds\":\"1553808833\"},\"primaryType\":\"Order\"}"
    val signature = magic.web3jSigExt.signTypedData(account, jsonString).send()
    Log.d("Magic", "Signature: " + signature.result)
  }
}

Sign Typed Data v4

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic
  lateinit var web3j: Web3j
  lateinit var gethWeb3j: Geth

  // After user is successfully authenticated
  private var account: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
  }

  fun signTypedDataV4(v: View) {
    val jsonString = "{\"domain\":{\"chainId\":1,\"name\":\"Ether Mail\",\"verifyingContract\":\"0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC\",\"version\":\"1\"},\"message\":{\"contents\":\"Hello, Bob!\",\"from\":{\"name\":\"Cow\",\"wallets\":[\"0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826\",\"0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF\"]},\"to\":[{\"name\":\"Bob\",\"wallets\":[\"0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB\",\"0xB0BdaBea57B0BDABeA57b0bdABEA57b0BDabEa57\",\"0xB0B0b0b0b0b0B000000000000000000000000000\"]}]},\"primaryType\":\"Mail\",\"types\":{\"EIP712Domain\":[{\"name\":\"name\",\"type\":\"string\"},{\"name\":\"version\",\"type\":\"string\"},{\"name\":\"chainId\",\"type\":\"uint256\"},{\"name\":\"verifyingContract\",\"type\":\"address\"}],\"Group\":[{\"name\":\"name\",\"type\":\"string\"},{\"name\":\"members\",\"type\":\"Person[]\"}],\"Mail\":[{\"name\":\"from\",\"type\":\"Person\"},{\"name\":\"to\",\"type\":\"Person[]\"},{\"name\":\"contents\",\"type\":\"string\"}],\"Person\":[{\"name\":\"name\",\"type\":\"string\"},{\"name\":\"wallets\",\"type\":\"address[]\"}]}}"
    val signature = magic.web3jSigExt.signTypedDataV4(account, jsonString).send()
    Log.d("Magic", "Signature: " + signature.result)
  }
}

Get User Info

Kotlin

class MagicActivity: AppCompatActivity() {
  lateinit var web3j: Web3j

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
    web3j = Web3j.build(magic.rpcProvider)
  }

  // After user is successfully authenticated
  fun getAccount(){
    try {
      val accounts = web3j.ethAccounts().sendAsync()

      accounts.whenComplete { accRepsonse: EthAccounts?, error: Throwable? ->
        if (error != null) {
          Log.e("MagicError", error.localizedMessage)
        }
        if (accRepsonse != null && !accRepsonse.hasError()) {
          account = accRepsonse.accounts[0]
          Log.d("Magic", "Your address is $account")
        }
      }
    } catch (e: Exception) {
      Log.e("Error", e.localizedMessage)
    }
  }
}

Smart Contract

In this example, we’ll be demonstrating how to use Magic with Web3j to interact with Solidity smart contracts. The simple Hello World contract allows anyone to read and write a message to it.

Solidity

pragma solidity ^0.5.10;

contract HelloWorld {
  string public message;

  constructor(string memory initMessage) public {
    message = initMessage;
  }

  function update(string memory newMessage) public {
    message = newMessage;
  }
}

Create a Kotlin/Java Contract Class from ABI

Web3j supports the auto-generation of smart contract function wrappers in Java from Solidity ABI files. To get started, you must have two files

ABI JSON file <Contract>.json
ByteCode file <Contract>.bin

Install web3j cli-tool

Bash

curl -L https://get.web3j.io | sh

You may need to install a JDK to support this library

After it has been installed to your computer, you may run the following command to check

Bash

web3j version

Create the contract class

Bash

web3j solidity generate -a=./path/to/<Contract>.json -b=./path/to/<Contract>.bin -o=/output/path/ -p={packageName}

You’ll find a Contract.java file created in your output directory above. Put this file in your project, and no more changes are needed. For more details about this section, please click here.

Deploy Contract

When deploying contract, building or interacting with a contract using web3j library, Magic offers MagicTxnManager class as a default TransactionManager that helps you to avoid dealing with private keys or credentials that Contract class requires.

Kotlin

import link.magic.demo.contract.Contract // This is the contract class you created above

class MagicActivity: AppCompatActivity() {
  lateinit var magic: Magic
  lateinit var web3j: Web3j

  // After user is successfully authenticated
  private var account: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    magic = (applicationContext as MagicDemoApp).magic
    web3j = Web3j.build(magic.rpcProvider)
  }

  fun deployContract(view: View) {
    try {
      val price = BigInteger.valueOf(22000000000L)
      val limit = BigInteger.valueOf(4300000)
      val gasProvider = StaticGasProvider(price, limit)
      val contract = Contract.deploy(
        web3j,
        account?.let { MagicTxnManager(web3j, it) },
        gasProvider,
        "HELLO_WORLD_FROM_ANDROID"
      ).send()
      Log.d("Magic", "Deploy to" + contract.contractAddress)
    } catch (e: Exception) {
      Log.e("E", "error", e)
    }
  }
}

Read From Contract

Kotlin

fun contractRead(view: View) {
  try {
    val price = BigInteger.valueOf(22000000000L)
    val limit = BigInteger.valueOf(4300000)
    val gasProvider = StaticGasProvider(price, limit)

    // Contract in testnet
    val contract = ExampleContract.load("0x6a2d321a3679b1b3c8a19b84e41abd11763a8ab5", web3j, account?.let { MagicTxnManager(web3j, it) }, gasProvider)
    if (contract.isValid) {
      val ethCall = contract.message().send()
      Log.d("Magic", ethCall.toString())
    } else {
      throw Error("contract not valid")
    }
  } catch (e: Exception) {
    Log.e("E", "error", e)
  }
}

Write to Contract

Kotlin

fun contractWrite(view: View) {
  try {
    val price = BigInteger.valueOf(22000000000L)
    val limit = BigInteger.valueOf(4300000)
    val gasProvider = StaticGasProvider(price, limit)

    // Contract in testnet
    val contract = ExampleContract.load("0x6a2d321a3679b1b3c8a19b84e41abd11763a8ab5", web3j, account?.let { MagicTxnManager(web3j, it) }, gasProvider)
    if (contract.isValid) {
      val ethCall = contract.update("NEW_MESSAGE_FROM_ANDROID").send()
      Log.d("Magic", ethCall.toString())
    } else {
      throw Error("contract not valid")
    }
  } catch (e: Exception) {
    Log.e("E", "error", e)
  }
}

Resources

Magic Android SDK

​Installation

​Initialization

​Use Different Networks

​Testnet

​Custom Node

​Associated Class

​Common Methods

​Send Transaction

​Sign Message

​Personal Sign

​Sign TypedData Legacy (V1)

​Sign Typed Data v3

​Sign Typed Data v4

​Get User Info

​Smart Contract

​Create a Kotlin/Java Contract Class from ABI

​Install web3j cli-tool

​Create the contract class

​Deploy Contract

​Read From Contract

​Write to Contract

​Resources

Installation

Initialization

Use Different Networks

Testnet

Custom Node

Associated Class

Common Methods

Send Transaction

Sign Message

Personal Sign

Sign TypedData Legacy (V1)

Sign Typed Data v3

Sign Typed Data v4

Get User Info

Smart Contract

Create a Kotlin/Java Contract Class from ABI

Install web3j cli-tool

Create the contract class

Deploy Contract

Read From Contract

Write to Contract

Resources