Android Integration Guide

Wallet Core is available on the Android platform, through Java/JNI bindings. In this guide we show how to use it.

A sample application is available at: https://github.com/trustwallet/wallet-core/tree/master/samples/android .

Prerequisites

• Android Studio
• Android NDK Support plugin

Adding Library Dependency

Android releases are hosted on GitHub packages, It needs authentication to download packages, please checkout this guide from GitHub for more details.

We recommend to create a non-expiring and readonly token for accessing GitHub packages, and add it to local.properties of your Android Studio project locally.

Generate a token here:

Add this dependency to build.gradle:

dependencies {
    implementation "com.trustwallet:wallet-core:<latest_tag>"
}

Add maven and credentials (local.properties for local or system environment variables CI)

Properties properties = new Properties()
File localProps = new File(rootDir.absolutePath, "local.properties")
if (localProps.exists()) {
    properties.load(localProps.newDataInputStream())
} else {
    println "local.properties not found"
}

allprojects {
    repositories {
        maven {
            url = uri("https://maven.pkg.github.com/trustwallet/wallet-core")
            credentials {
                username = properties.getProperty("gpr.user") as String?: System.getenv("GITHUB_USER")
                password = properties.getProperty("gpr.key") as String?: System.getenv("GITHUB_TOKEN")
            }
        }
    }
}

Code Examples

In the following sections we show code examples for some common funcions. Please refer to the Wallet Usage Guide for detailed explanations.

Wallet Management

First thing we need is to load JNI library

init {
    System.loadLibrary("TrustWalletCore")
}

Creating or Importing a Multi-Coin HD Wallet

val wallet = HDWallet(128, "")

val wallet = HDWallet("ripple scissors kick mammal hire column oak again sun offer wealth tomorrow wagon turn fatal", "")

Account Address Derivation

Generating the Default Address for a Coin

val addressBTC = wallet.getAddressForCoin(CoinType.BITCOIN)
val addressETH = wallet.getAddressForCoin(CoinType.ETHEREUM)

Generating an Address Using a Custom Derivation Path (Expert)

val key = wallet.getKey(CoinType.ETHEREUM, "m/44\'/60\'/1\'/0/0")   // m/44'/60'/1'/0/0
val address = CoinType.ETHEREUM.deriveAddress(key)

Transaction Signing

In general, when creating a new blockchain transaction, a wallet has to:

1. Put together a transaction with relevant fields (source, target, amount, etc.)
2. Sign the transaction, using the account private key. This is done by Wallet Core.
3. Send to a node for broadcasting to the blockchain network.

Ethereum Transaction Signing

Code example to fill in signer input parameters, perform signing, and retrieve encoded result:

val signerInput = Ethereum.SigningInput.newBuilder().apply {
    chainId = ByteString.copyFrom(BigInteger("01").toByteArray())
    gasPrice = BigInteger("d693a400", 16).toByteString() // decimal 3600000000
    gasLimit = BigInteger("5208", 16).toByteString()     // decimal 21000
    toAddress = dummyReceiverAddress
    transaction = Ethereum.Transaction.newBuilder().apply {
       transfer = Ethereum.Transaction.Transfer.newBuilder().apply {
           amount = BigInteger("0348bca5a16000", 16).toByteString()
       }.build()
    }.build()
    privateKey = ByteString.copyFrom(secretPrivateKey.data())
}.build()
val output = AnySigner.sign(signerInput, CoinType.ETHEREUM, Ethereum.SigningOutput.parser())
println("Signed transaction: \n${output.encoded.toByteArray().toHexString()}")