React Native HID (Android only) | Developers

React Native HID (Android only)

Estimated reading time: More than 10 minutes

Introduction

In this section, you will see how to create a React Native application using the @ledgerhq/react-native-hid (Only on Android). For this project some general prerequisites are mandatory and you can find them here.

Then you can now go through the prerequisite for Android development below.

Prerequisites

Android Studio Installation

Download and install Android Studio, choose the version of your operating system.

When Android Studio is installed, open it.

Android Studio Window
Fig. 1: Android Studio Window

Go to Settings => Appearance & Behavior => System Settings => Android SDK and check the “Show Package Details” checkbox on the bottom right of the windows.

Android Studio Settings
Fig. 2: Android Studio Settings

Install the latest SDK version. To do so, select the packages shown below and click apply.

Android Studio SDK Settings
Fig. 3: Android Studio SDK Settings

Install Homebrew

Homebrew is a package manager for macOS. When it needs to install software from third-party websites. To install it, run:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"

Install watchman

React Native uses watchman to detect real-time code changes and it automatically builds and pushes the update to your device without manually refreshing.

brew install watchman

Install Java JRE and JDK

There is a risk of react-native build failure if you don’t have a complete installation of Java. Downloading Android Studio is not enough since it comes bundled with its own JRE.

brew install --cask adoptopenjdk/openjdk/adoptopenjdk8

Install React Native

With React Native, you can write an application in Javascript and then the React Native Compiler will convert your Javascript code into native code for iOS and Android environments. React Native command line interface can be installed using npm as below.

npm install -g react-native-cli

Set the environnement variables

If you are using bash, put the environment variable into the bash_profile as below:

cd ~/
touch ~/.bash_profile;
open -e .bash_profile
export ANDROID_HOME=$HOME/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/emulator
export PATH=$PATH:$ANDROID_HOME/tools
export PATH=$PATH:$ANDROID_HOME/tools/bin
export PATH=$PATH:$ANDROID_HOME/platform-tools

Do the same if you are using zsh or anything else. Remember the file will be named differently (eg. zsh => .zprofile)

Android App Build

Now that we have set up the prerequisites, you can now create the application. In this integration, we will use the ethereum application.

Project Initialization

First, open a terminal and create a new project. For this tutorial the project will be named “myApp”.

Run:

react-native init myApp
cd myApp
Tip
During the initialization, required 'CocoaPods' dependencies are installed and it may take time.

Code Implementation

Run:

touch App.js
touch polyfill.js

Open your folder in a code editor, it must look like this.

Folder of the Application
Fig. 4: Folder of the Application

polyfill.js

In polyfill.js copy-paste the following code:

global.Buffer = require("buffer").Buffer;

index.js

Then import the “polyfill.js” in “index.js” as shown below:

/**
 * @format
 */

import "./polyfill";    //import this
import {AppRegistry} from 'react-native';
import App from './App';
import {name as appName} from './app.json';

AppRegistry.registerComponent(appName, () => App);

App.js

In App.js copy-paste the following code:

import React, { Component } from "react";
import { StyleSheet, Text, View } from "react-native";
import { listen } from "@ledgerhq/logs";

import TransportHID from "@ledgerhq/react-native-hid";
import AppEth from "@ledgerhq/hw-app-eth";


// This is helpful if you want to see BLE logs. (only to use in dev mode)

class App extends Component {
  state = {
    transport: null
  };


  onSelectDevice = async () => {
    try {
      const transport = await TransportHID.create();
      listen(log => console.log(log));
      const eth = new AppEth(transport);
      const path = "44'/60'/0'/0/0"; // HD derivation path
      const { address } = await eth.getAddress(path, false);
      this.setState({ transport: address });
      await eth.getAddress(path, true);
    } catch (e) {
      throw new Error(e);
      return null;
    }
  };

  render() {
    const { transport } = this.state;
     if(!transport){
       return (
        <View style={styles.header}>
          <Text style={styles.headerTitle}>Scanning for Ledger...</Text>
          <Text style={styles.headerSubtitle} onPress={() => {this.onSelectDevice()}}>
            Power up your Ledger and enter your pin. Then tap the screen
          </Text>
        </View>
      );
    }else{
      return (<View style={styles.header}>
        <Text style={styles.title}>Ledger Live Ethereum Account 1</Text>
        <Text style={styles.headerTitle}>
          {transport}
        </Text>
      </View>
      );
    }
  };
}

export default App;



const styles = StyleSheet.create({
  header: {
    paddingTop: 80,
    paddingBottom: 36,
    alignItems: "center"
  },
  headerTitle: {
    fontSize: 22,
    marginBottom: 16
  },
  headerSubtitle: {
    fontSize: 12,
    color: "#999"
  },
  list: {
    flex: 1
  },
  errorTitle: {
    color: "#c00",
    fontSize: 16,
    marginBottom: 16
  }
});

Dependencies Installation

Run:

npm install --save buffer
npm install --save @ledgerhq/logs
npm install --save @ledgerhq/hw-app-eth
npm install --save @ledgerhq/hw-transport-webusb
Package What does it do?
Buffer
@ledgerhq/logs It helps you ask your Ledger device to access the ethereum address.
@ledgerhq/hw-app-eth It helps you ask your Ledger device to access the ethereum address.
@ledgerhq/react-native-hid It provides you with all the methods to interact with your Ledger with an HID connexion.

Package.json dependencies

Now that the dependencies are installed you can find them in the “package.js”. This is how your “package.json” must look like.

{
  "name": "myApp",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "android": "react-native run-android",
    "ios": "react-native run-ios",
    "start": "react-native start",
    "test": "jest",
    "lint": "eslint ."
  },
  "dependencies": {
    "@ledgerhq/hw-app-eth": "^6.15.2",
    "@ledgerhq/logs": "^6.10.0",
    "@ledgerhq/react-native-hid": "^6.11.2",
    "buffer": "^6.0.3",
    "react": "17.0.2",
    "react-native": "0.66.3"
  },
  "devDependencies": {
    "@babel/core": "^7.16.0",
    "@babel/runtime": "^7.16.3",
    "@react-native-community/eslint-config": "^3.0.1",
    "babel-jest": "^27.3.1",
    "eslint": "^8.3.0",
    "jest": "^27.3.1",
    "metro-react-native-babel-preset": "^0.66.2",
    "react-test-renderer": "17.0.2"
  },
  "jest": {
    "preset": "react-native"
  }
}

Build.gradle Modification

In “build.gradle”, in the “android” folder change minSdkVersion = 21 to minSdkVersion = 24.

Build.gradle Modify the minSdkVersion
Fig. 5: Build.gradle Modify the minSdkVersion

You can now test the application you have built.

Android App Test

The app testing will be executed on your smartphone because the android studio environment does not allow you to use either Bluetooth or USB connexion.

Tip
Please refer to the information for Android Emulator Limitation .

Enable Developer Settings

To integrate an application on your android smartphone you have to enable the developer role. To do that go to Settings > About Phone > Build Number, and tap 7 times on build number to enable the developer settings.

Then go to Settings > System > Advanced > Developer Options and enable the “USB debugging” as well as “Install via USB”

Connect your phone to your computer, and run the below command to see if your device is connected:

adb devices

If all goes well, the list of devices is displayed as shown below:

Device Connected On The Machine
Fig. 6: Device Connected On The Machine

Tip
For more information about enabling the developer settings on your android device go to android studio docs .

Start the Development Server

You can now open a terminal, navigate to your “myApp” folder, and start the server by running:

npm start

Install the App on Device

Keep the terminal where “metro” is running open and open a new terminal. In this new terminal go to your app folder:

cd myApp

Run the command below to install the application on your android device. It’s assumed that your device is recognized by the command adb devices as the Previous Step mentioned.

npm run android

A window will pop up on your android device to install the application. Click on “Yes” to install it and run it.

When launching the application it will be displayed like the image below.

Application Displayed on Smartphone
Fig. 7: Application Displayed on Smartphone

Plug Your Nano

Connect your Ledger Nano to your android device, unlock it and open the ethereum application. The steps are described below.

Nano Enter Code Pin
Fig. 8: Nano Enter Code Pin

Nano Application
Fig. 9: Nano Application

Nano Run Application
Fig. 10: Nano Run Application

Now that the two devices are connected, the address will be displayed as shown below:

Address Account Displayed on Smartphone
Fig. 11: Address Account Displayed on Smartphone

Congratulations you have successfully built your first application connected with Ledger!


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Getting Started
Theme Features
Customization