Cannot Create BLE Manager

Question

Hello I am new at React Native and in my application I am trying to scan ble devices and list their names on screen. In code sources people most commonly create a Bluetooth Low Energy Manager as const manager = new BleManager(); but when I tried this code (and of course other ways too) it gives error like

TypeError: null is not an object (evaluating '_BleModule.BleModule.createClient')

This error is located at:
    in HelloWorldApp (created by ExpoRoot)
    in ExpoRoot
    in RCTView (created by View)
    in View (created by AppContainer)
    in RCTView (created by View)
    in View (created by AppContainer)
    in AppContainer
at node_modules\react-native\Libraries\LogBox\LogBox.js:149:8 in registerError
at node_modules\react-native\Libraries\LogBox\LogBox.js:60:8 in errorImpl
at node_modules\react-native\Libraries\LogBox\LogBox.js:34:4 in console.error
at node_modules\expo\build\environment\react-native-logs.fx.js:27:4 in error
at node_modules\react-native\Libraries\Core\ExceptionsManager.js:104:6 in reportException
at node_modules\react-native\Libraries\Core\ExceptionsManager.js:172:19 in handleException
at node_modules\react-native\Libraries\Core\ReactFiberErrorDialog.js:43:2 in showErrorDialog
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:15792:34 in logCapturedError        
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:15884:20 in update.callback
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:7199:2 in callCallback
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:7220:20 in commitUpdateQueue
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:16632:25 in commitLifeCycles        
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19216:22 in commitLayoutEffects     
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:93:4 in invokeGuardedCallbackProd
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:318:2 in invokeGuardedCallback      
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18952:29 in commitRootImpl
at node_modules\scheduler\cjs\scheduler.development.js:468:23 in unstable_runWithPriority
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18791:17 in commitRoot
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18192:12 in performSyncWorkOnRoot   
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5911:33 in runWithPriority$argument_1
at node_modules\scheduler\cjs\scheduler.development.js:468:23 in unstable_runWithPriority
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5906:23 in flushSyncCallbackQueueImpl
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5893:28 in flushSyncCallbackQueue
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:17745:30 in scheduleUpdateOnFiber   
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:21484:23 in updateContainer
at node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:22144:17 in render
at node_modules\react-native\Libraries\ReactNative\renderApplication.js:58:4 in renderApplication
at node_modules\react-native\Libraries\ReactNative\AppRegistry.js:117:25 in runnables.appKey.run
at node_modules\react-native\Libraries\ReactNative\AppRegistry.js:202:4 in runApplication
at node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:414:4 in __callFunction
at node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:113:6 in __guard$argument_0
at node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:365:10 in __guard
at node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:112:4 in callFunctionReturnFlushedQueue

Here is my code that I tried to create a manager:

import { StatusBar } from 'expo-status-bar';
import React, { Component } from 'react';
import { StyleSheet, Text, View } from 'react-native';
import { BleManager } from 'react-native-ble-plx';

const HelloWorldApp = () => {
  const manager = new BleManager();

I cannot solve where is my mistake. Please anyone can help me to solve this issue?

Note: I also installed ble-plx package using npm install --save react-native-ble-plx command.

Note2:I created my project using expo.

Are you using Android or iOS? In case of android: have you added the repositoy to your build.gradle according to https://github.com/dotintent/react-native-ble-plx#android-example-setup ? — Michael Kotzjan, Dec 07 '21 at 09:49
I created my project using ``expo init ProjectA`` command. So my project does not have a file named 'androidManifest.xml' or 'build.gradle'. I also created another project using ``npx create-react-native-app ProjectB`` but this project did not work too (It did not produce a QR code). — elifnurafsar, Dec 07 '21 at 11:35
I'm not familiar with expo, maybe [edit] your question and add this information. Take a look at this for example: https://github.com/dotintent/react-native-ble-plx/issues/615 thee are other developers with expo BLE problems — Michael Kotzjan, Dec 07 '21 at 11:51

score 1 · Accepted Answer · answered May 27 '22 at 04:51

1

You might need to ask the user for permission before using Bluetooth. Add these to your android-manifest.xml :

<uses-feature android:name="android.hardware.bluetooth" android:required="true"/>
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>

answered May 27 '22 at 04:51

Ethan Stacey

26
1

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community May 28 '22 at 17:40

score 0 · Answer 2 · answered May 25 '22 at 14:14

0

You are getting this error because of the expo. Expo does not support the ble-manager ble-plx package. You need to create a native project via

npx react-native init AwesomeProject

answered May 25 '22 at 14:14

Sachin Saini

359
2
10

Cannot Create BLE Manager

2 Answers2