React Native Bluetooth on iOS (Nano X only)

Introduction

In this section, you will see how to create a React Native application using the @ledgerhq/react-native-hw-transport-ble (opens in a new tab). For this project some general prerequisites are mandatory and you can find them here.

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

One-time setup

Environnement

Make sure you go through:

the Development Prerequisites.
the Mobile Environment Setup.

App Coding

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

App setup

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

Run:

react-native init myiOSBTApp
cd myiOSBTApp

ℹ️

The dependencies of 'CocoaPods' may take some time to initialize.

Files

Run:

mkdir src
touch polyfill.js
touch src/DeviceItem.js
touch src/DeviceSelectionScreen.js
touch src/ShowAddressScreen.js

polyfill.js

In "polyfill.js", copy-paste the following code:

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

index.js

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

/**
 * @format
 */
 
import "./polyfill";    //import this
import {AppRegistry} from 'react-native';
import App from './src/App';    //modify this import
import {name as appName} from './app.json';
 
AppRegistry.registerComponent(appName, () => App);

App.js

Move the file named "App.js" in the "src" folder and copy-paste the following code:

import React, { Component } from "react";
 
import DeviceSelectionScreen from "./DeviceSelectionScreen";
import ShowAddressScreen from "./ShowAddressScreen";
 
import TransportBLE from "@ledgerhq/react-native-hw-transport-ble";
 
// 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 device => {
    const transport = await TransportBLE.open(device);
    transport.on("disconnect", () => {
      // Intentionally for the sake of simplicity we use a transport local state
      // and remove it on disconnect.
      // A better way is to pass in the device.id and handle the connection internally.
      this.setState({ transport: null });
    });
    this.setState({ transport });
  };
 
  render() {
    const { transport } = this.state;
    if (!transport) {
      return <DeviceSelectionScreen onSelectDevice={this.onSelectDevice} />;
    }
    return <ShowAddressScreen transport={transport} />;
  }
}
 
export default App;

In "DeviceItem.js" copy-paste the following code:

import React, { Component } from "react";
import {
  Text,
  TouchableOpacity,
  StyleSheet,
  ActivityIndicator
} from "react-native";
 
class DeviceItem extends Component {
  state = {
    pending: false
  };
  onPress = async () => {
    this.setState({ pending: true });
    try {
      await this.props.onSelect(this.props.device);
    } finally {
      this.setState({ pending: false });
    }
  };
 
  render() {
    const { device } = this.props;
    const { pending } = this.state;
    return (
      <TouchableOpacity
        style={styles.deviceItem}
        onPress={this.onPress}
        disabled={pending}
      >
        <Text style={styles.deviceName}>{device.name}</Text>
        {pending ? <ActivityIndicator /> : null}
      </TouchableOpacity>
    );
  }
}
export default DeviceItem;
 
const styles = StyleSheet.create({
  deviceItem: {
    paddingVertical: 16,
    paddingHorizontal: 32,
    marginVertical: 8,
    marginHorizontal: 16,
    borderColor: "#ccc",
    borderWidth: 1,
    flexDirection: "row",
    alignItems: "center",
    justifyContent: "space-between"
  },
  deviceName: {
    fontSize: 20,
    fontWeight: "bold"
  }
});

In "DeviceSelectionScreen.js", copy-paste the following code:

import React, { Component } from "react";
import {
  StyleSheet,
  Text,
  View,
  TouchableOpacity,
  FlatList,
  Platform,
  PermissionsAndroid
} from "react-native";
import { Observable } from "rxjs";
import AppEth from "@ledgerhq/hw-app-eth";
import TransportBLE from "@ledgerhq/react-native-hw-transport-ble";
import QRCode from "react-native-qrcode-svg";
import DeviceItem from "./DeviceItem";
 
const deviceAddition = device => ({ devices }) => ({
  devices: devices.some(i => i.id === device.id)
    ? devices
    : devices.concat(device)
});
 
class DeviceSelectionScreen extends Component {
  state = {
    devices: [],
    error: null,
    refreshing: false
  };
 
  async componentDidMount() {
    // NB: this is the bare minimal. We recommend to implement a screen to explain to user.
    if (Platform.OS === "android") {
      await PermissionsAndroid.request(
        PermissionsAndroid.PERMISSIONS.ACCESS_COARSE_LOCATION
      );
    }
    let previousAvailable = false;
    new Observable(TransportBLE.observeState).subscribe(e => {
      if (e.available !== previousAvailable) {
        previousAvailable = e.available;
        if (e.available) {
          this.reload();
        }
      }
    });
 
    this.startScan();
  }
 
  componentWillUnmount() {
    if (this.sub) this.sub.unsubscribe();
  }
 
  startScan = async () => {
    this.setState({ refreshing: true });
    this.sub = new Observable(TransportBLE.listen).subscribe({
      complete: () => {
        this.setState({ refreshing: false });
      },
      next: e => {
        if (e.type === "add") {
          this.setState(deviceAddition(e.descriptor));
        }
        // NB there is no "remove" case in BLE.
      },
      error: error => {
        this.setState({ error, refreshing: false });
      }
    });
  };
 
  reload = async () => {
    if (this.sub) this.sub.unsubscribe();
    this.setState(
      { devices: [], error: null, refreshing: false },
      this.startScan
    );
  };
 
  keyExtractor = (item: *) => item.id;
 
  onSelectDevice = async device => {
    try {
      await this.props.onSelectDevice(device);
    } catch (error) {
      this.setState({ error });
    }
  };
 
  renderItem = ({ item }: { item: * }) => {
    return <DeviceItem device={item} onSelect={this.onSelectDevice} />;
  };
 
  ListHeader = () => {
    const { error } = this.state;
    return error ? (
      <View style={styles.header}>
        <Text style={styles.headerTitle}>Sorry, an error occured</Text>
        <Text style={styles.errorTitle}>{String(error.message)}</Text>
      </View>
    ) : (
      <View style={styles.header}>
        <Text style={styles.headerTitle}>Scanning for Bluetooth...</Text>
        <Text style={styles.headerSubtitle}>
          Power up your Ledger Nano X and enter your pin.
        </Text>
      </View>
    );
  };
 
  render() {
    const { devices, error, refreshing } = this.state;
 
    return (
      <FlatList
        extraData={error}
        style={styles.list}
        data={devices}
        renderItem={this.renderItem}
        keyExtractor={this.keyExtractor}
        ListHeaderComponent={this.ListHeader}
        onRefresh={this.reload}
        refreshing={refreshing}
      />
    );
  }
}
 
export default DeviceSelectionScreen;
 
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
  }
});

In "ShowAddressScreen.js", copy-paste the following code:

import React, { Component } from "react";
import { StyleSheet, Text, View } from "react-native";
 
import AppEth from "@ledgerhq/hw-app-eth";
import TransportBLE from "@ledgerhq/react-native-hw-transport-ble";
import QRCode from "react-native-qrcode-svg";
 
const delay = ms => new Promise(success => setTimeout(success, ms));
 
class ShowAddressScreen extends Component {
  state = {
    error: null,
    address: null
  };
 
  async componentDidMount() {
    while (!this.state.address) {
      if (this.unmounted) return;
      await this.fetchAddress(false);
      await delay(500);
    }
    await this.fetchAddress(true);
  }
 
  async componentWillUnmount() {
    this.unmounted = true;
  }
 
  fetchAddress = async verify => {
    const { transport } = this.props;
    try {
      const eth = new AppEth(transport);
      const path = "44'/60'/0'/0/0"; // HD derivation path
      const { address } = await eth.getAddress(path, verify);
      if (this.unmounted) return;
      this.setState({ address });
    } catch (error) {
      // in this case, user is likely not on Ethereum app
      if (this.unmounted) return;
      this.setState({ error });
      return null;
    }
  };
 
  render() {
    const { address, error } = this.state;
 
    return (
      <View style={styles.ShowAddressScreen}>
        {!address ? (
          <>
            <Text style={styles.loading}>Loading your Ethereum address...</Text>
            {error ? (
              <Text style={styles.error}>
                A problem occurred, make sure to open the Ethereum application
                on your Ledger Nano X. (
                {String((error && error.message) || error)})
              </Text>
            ) : null}
          </>
        ) : (
          <>
            <Text style={styles.title}>Ledger Live Ethereum Account 1</Text>
            <QRCode value={address} size={300} />
            <Text style={styles.address}>{address}</Text>
          </>
        )}
      </View>
    );
  }
}
 
export default ShowAddressScreen;
 
const styles = StyleSheet.create({
  ShowAddressScreen: {
    flex: 1,
    padding: 16,
    alignItems: "center",
    justifyContent: "center"
  },
  error: {
    color: "#c00",
    fontSize: 16
  },
  loading: {
    color: "#999",
    fontSize: 16
  },
  title: {
    fontSize: 22,
    marginBottom: 16
  },
  address: {
    marginTop: 16,
    color: "#555",
    fontSize: 14
  }
});

Your folder will look like this.

Fig. 3: Folder of the Application

Dependencies

Installation

Run:

npm install --save react-native-qrcode-svg
npm install --save react-native-svg
npm install --save rxjs
npm install --save @ledgerhq/react-native-hw-transport-ble
npm install --save react-native-ble-plx
npx react-native link react-native-ble-plx
npm install --save buffer
npm install --save @ledgerhq/hw-app-eth

Package	What it does
react-native-qrcode-svg (opens in a new tab)	It allows you to create a QR code.
react-native-svg (opens in a new tab)	It is a mandatory package to use react-native-qrcode-svg
rxjs (opens in a new tab)	It is a rewrite of "Reactive-Extensions/RxJS" and is the latest production-ready version of RxJS.
@ledgerhq/hw-transport-web-ble (opens in a new tab)	It provides you with all the methods to interact with your Ledger Nano X with a Bluetooth connexion.
react-native-ble-plx (opens in a new tab)	It scans the bluetooth devices.
buffer (opens in a new tab)	The goal is to provide an API that is 100% identical to node's Buffer API.
hw-app-eth (opens in a new tab)	It helps you ask your Ledger device to access the ethereum address.

package.json

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

{
  "name": "myiOSBTApp",
  "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": "^6.16.2",
    "@ledgerhq/react-native-hw-transport-ble": "^6.15.0",
    "buffer": "^6.0.3",
    "react": "17.0.2",
    "react-native": "0.66.3",
    "react-native-ble-plx": "^2.0.3",
    "react-native-qrcode-svg": "^6.1.1",
    "react-native-svg": "^12.1.1",
    "rxjs": "^7.4.0"
  },
  "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"
  }
}

Pod Installation

Then the pod has to be installed in the "ios" folder:

cd ios/
pod install
pod update

Enable Bluetooth

Launch Xcode and open the ios folder in the "myiOSBTApp" folder to add the "NSBluetoothAlwaysUsageDescription" key to the "info.plist".

Fig. 4: Open a Project on Xcode

Fig. 5: Choose the Project

Fig. 6: Add NSBluetoothAlwaysUsageDescription in info.plist

You can now test the application you have built.

App Launch

App testing is done on your smartphone because the Xcode emulator cannot use Bluetooth or USB connexions.

💡

Please refer to the information for iOS Emulator limitation (opens in a new tab).

Build the App

To build your application on your Apple device you have to connect Xcode to an Apple account as shown below.

Fig. 7: Connect Xcode to an Apple Account

Then connect your Apple device to your computer to build the application directly on the Apple device. If all goes well the device name will be displayed on the top of the Xcode window, all you have to do is click on the triangle icon on the top left corner to build the app on your Apple device.

Fig. 8: Build the Application

Trusting the Apple Development

To accept the installation of the application. You have to trust the "Apple development" on your device. Follow the steps below.

Iphone Settings 5 — *Fig. 9: Trusting the Apple Development*

You can finally test the application by launching it.

Launching the Application

When launching the application it will be displayed as shown below. You must have the Bluetooth and location activated.

Pairing the Ledger Nano X

To pair your Ledger Nano X you must unlock it.

Pair the Ledger Nano X to your Apple device.

Pairing and Launching the Ethereum App on the Nano X

The pairing code displayed on your Ledger Nano X needs to be confirmed.

Now that the pairing is done, the Nano X is ready with the ethereum application. If all goes well you must see the address of your ethereum account displayed.

*Fig. 16: Address Account Displayed on Smartphone*

Verify the Address

For security purposes, we display on your Nano X the same ethereum address for you to confirm.

Congratulations you have successfully built your first iOS Bluetooth application connected to your Ledger!

React Native Bluetooth on Android (Nano X only)React Native HID (Android only)