BLE scanner application

This reposatory shows an example Android application for a bluetooth low energy scanner written is react native, using expo. Step by step I will guide you how to develop and deploy into production this application. The goal is to scan the nearby smartphones with enabled bluetooth (with different IDs) and estimate it's relative distance for each source. Nowadays the electric rollers (scooters) are great risk to car traffic. The aim is to alarm the smartphone users (cars), to prepare the nearby scooter traffic. Therefore I implemented a separate mode for cars (scan) and another mode for scooters (beacon) in the same application.

1. Install Expo go on your Android smartphone

https://play.google.com/store/apps/details?id=host.exp.exponent

2. Enable Developer mode on your Android smartphone

https://developer.android.com/studio/debug/dev-options

3. Connect your Android smartphone to your computer via USB cable

4. Install Node.js on your computer

https://nodejs.org/en

Set the necessary environmental variables.

5. Install GIT in your computer

Make you sure to choose that option during the installation which command line interface supports git commands.

https://git-scm.com

6. Install Android Studio on your computer

https://developer.android.com/studio/install

Set the necessary environmental variables.

7. Install Java Development Kit (JDK) 20 on your computer

https://www.oracle.com/java/technologies/javase/jdk20-archive-downloads.html

Set the necessary environmental variables.

8. Make an account on Expo dev

https://expo.dev

9. Project setup using Expo

npx create-expo-app@latest

10. Install the react native react-native-ble-manager library

cd <project_name>

npx expo install react-native-ble-manager

11. In your app.json file extend the plugin config to enable the package work.

"plugins": [
      "expo-router",
      [
        "react-native-ble-manager",
        {
          "isBleRequired": true,
          "neverForLocation": true,
          "companionDeviceEnabled": false,
          "bluetoothAlwaysPermission": "Allow BLE DEMO APP to connect to bluetooth devices"
        }
      ]
]

12 Create your eas.json file

{
  "cli": {
    "version": ">= 3.9.0"
  },
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal",
      "ios": {
        "resourceClass": "m-medium"
      },
      "channel": "development"
    }
  }
}

13 Create prebuild

npx expo prebuild

14. Unplug device

15. Restart adb and remove adbkey

adb kill-server

Remove adbkey file from c:/Users/<Username>/.android

adb start-server

16. Plug device

17. Revoke USB debugging authorization, then disable USB debugging, and finally enable USB debugging on your smartphone

18. Starting the application in the development framework

npx expo run:android

This process will take sime time for the first run.

19. Have a look to the application

20. Install react-native-ble-plx

npx expo install react-native-ble-plx

21. Update your eas.json file

{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    },
    "preview": {
      "distribution": "internal"
    },
    "production": {}
  }
}

22. Install expo device

npx expo install expo-device

23. Add plugins to your app.json file

 "plugins": [
      [
        "react-native-ble-plx",
        {
          "isBackgroundEnabled": true,
          "modes": ["peripheral", "central"],
          "bluetoothAlwaysPermission": "Allow $(PRODUCT_NAME) to connect to bluetooth devices"
        }
      ]
    ]

24. Install eas-cli

npx npm install eas-cli

25 Install expo-dev-client

npx expo install expo-dev-client

26 Install react-native-background-timer

npm install react-native-background-timer

27 Install react-native-ble-advertiser

npm install react-native-ble-advertiser

28. Do the software development

29. Create prebuild

npx expo prebuild

30. Update your AndroidManifest.xml

Locate and update your AndroidManifest.xml from <project_name>\android\app\src\main\AndroidManifest.xml

<!-- Required for BLE on Android 12+ -->
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation"/>
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />
<!-- Required for older Android versions -->
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>

30. Update your build.gradle

Locate and update your build.gradle from <project_name>\node_modules\react-native-ble-advertiser\android\build.gradle

apply plugin: 'com.android.library'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
    }
}

dependencies {
    implementation 'com.facebook.react:react-native:+'
}

31. Starting the application in the development framework

npx expo run:android

At this point we finished doing the development and this reposatory contains every necessary files, except the node_modules and android folders because it's size. Now let's turn this into production. In production you will have unique credentials, therefore I do not want to include them.

32. Login to your expo dev profile

eas login

33. EAS build configuration

eas build:configure

34. Replace your eas.json file

{
  "cli": {
    "version": ">= 3.9.0"
  },
  "build": {
    "preview": {
      "android": {
        "buildType": "apk"
      }
    },
    "production": {},
    "development": {
      "developmentClient": true,
      "distribution": "internal",
      "ios": {
        "resourceClass": "m-medium"
      },
      "channel": "development"
    }
  }
}

35. EAS preview built

eas build -p android --profile preview

36. Build locally your .aab file (optional)

https://docs.expo.dev/guides/local-app-production/

37. Convert locally your .apk file from .aab file (optional)

https://stackoverflow.com/questions/53040047/generate-an-apk-file-from-an-aab-file-android-app-bundle

38. Copy and paste your .apk file to your Android smartphone and install it