flutter_blue_plus 1.10.1

Flutter plugin for connecting and communicationg with Bluetooth Low Energy devices, on Android and iOS

Note: this plugin is continuous work from FlutterBlue since maintenance stopped.

Foreward

For simple BLE apps, you should also consider QuickBlue (https://pub.dev/packages/quick_blue). Fewer features, smaller codebase.

Introduction

FlutterBluePlus is a bluetooth plugin for Flutter, a new app SDK to help developers build modern multi-platform apps.

Cross-Platform Bluetooth LE

FlutterBluePlus aims to offer the most from all supported platforms: iOS, macOS, Android. (Feel free to contribute Windows support!)

Usage

Error Handling

Flutter Blue Plus uses exceptions for error handling. Most functions can throw and must be handled.

See the Reference section below for a complete list of throwing function.

Scan for devices

// Start scanning
FlutterBluePlus.startScan(timeout: Duration(seconds: 4));

// Listen to scan results
var subscription = FlutterBluePlus.scanResults.listen((results) {
    // do something with scan results
    for (ScanResult r in results) {
        print('${r.device.localName} found! rssi: ${r.rssi}');
    }
});

// Stop scanning
FlutterBluePlus.stopScan();

Connect to a device

// Connect to the device
await device.connect();

// Disconnect from device
device.disconnect();

Discover services

List<BluetoothService> services = await device.discoverServices();
services.forEach((service) {
    // do something with service
});

Read and write characteristics

// Reads all characteristics
var characteristics = service.characteristics;
for(BluetoothCharacteristic c in characteristics) {
    List<int> value = await c.read();
    print(value);
}

// Writes to a characteristic
await c.write([0x12, 0x34])

Read and write descriptors

// Reads all descriptors
var descriptors = characteristic.descriptors;
for(BluetoothDescriptor d in descriptors) {
    List<int> value = await d.read();
    print(value);
}

// Writes to a descriptor
await d.write([0x12, 0x34])

Set notifications and listen to changes

await characteristic.setNotifyValue(true);
characteristic.onValueReceived.listen((value) {
    // do something with new value
});

Read the MTU and request larger size

final mtu = await device.mtu.first;
await device.requestMtu(512);

Note that iOS will not allow requests of MTU size, and will always try to negotiate the highest possible MTU (iOS supports up to MTU size 185)

Getting Started

Change the minSdkVersion for Android

flutter_blue_plus is compatible only from version 19 of Android SDK so you should change this in android/app/build.gradle:

Android {
  defaultConfig {
     minSdkVersion: 19

Add permissions for Bluetooth

We need to add the permission to use Bluetooth and access location:

Android

In the android/app/src/main/AndroidManifest.xml let’s add:

	  <uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" />
	  <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
 <application

By default the package does not request the ACCESS_FINE_LOCATION permission on Android 12+. In case you need to get the physical location of the device via Bluetooth, you need to add the permission to the android/app/src/main/AndroidManifest.xml:

	  <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
 <application

and set the androidUsesFineLocation flag to true when scanning:

// Start scanning
flutterBlue.startScan(timeout: Duration(seconds: 4), androidUsesFineLocation: true);

// Stop scanning
flutterBlue.stopScan();

IOS

In the ios/Runner/Info.plist let’s add:

	<dict>
	    <key>NSBluetoothAlwaysUsageDescription</key>
	    <string>Need BLE permission</string>
	    <key>NSBluetoothPeripheralUsageDescription</key>
	    <string>Need BLE permission</string>
	    <key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
	    <string>Need Location permission</string>
	    <key>NSLocationAlwaysUsageDescription</key>
	    <string>Need Location permission</string>
	    <key>NSLocationWhenInUseUsageDescription</key>
	    <string>Need Location permission</string>

For location permissions on iOS see more at: https://developer.apple.com/documentation/corelocation/requesting_authorization_for_location_services

Reference

FlutterBlue API

	Android	iOS	Description
scan	✅	✅	Starts a scan for Bluetooth Low Energy devices.
adapterState	✅	✅	Stream of state changes for the Bluetooth Adapter.
isAvailable	✅	✅	Checks whether the device supports Bluetooth.
isOn	✅	✅	Checks if Bluetooth functionality is turned on.

BluetoothDevice API

	Android	iOS	Description
connect	✅	✅	Establishes a connection to the device.
disconnect	✅	✅	Cancels an active or pending connection to the device.
discoverServices	✅	✅	Discovers services offered by the remote device as well as their characteristics and descriptors.
services	✅	✅	Gets a list of services. Requires that discoverServices() has completed.
connectionState	✅	✅	Stream of connection changes for the Bluetooth Device.
mtu	✅	✅	Stream of mtu size changes.
requestMtu	✅		Request to change the MTU for the device.
readRssi	✅	✅	Read RSSI from a connected device.
requestConnectionPriority	✅		Request to update a high priority, low latency connection. An application should only request high priority connection parameters to transfer large amounts of data over LE quickly.
removeBond	✅		Remove Bluetooth Bond of device
setPreferredPhy	✅		Set preferred RX and TX phy for connection and phy options

BluetoothCharacteristic API

	Android	iOS	Description
read	✅	✅	Retrieves the value of the characteristic.
write	✅	✅	Writes the value of the characteristic.
setNotifyValue	✅	✅	Sets notifications or indications on the characteristic.
onValueReceived	✅	✅	Stream of characteristic value changes
lastValueStream	✅	✅	Stream of lastValue + characteristic value changes

BluetoothDescriptor API

	Android	iOS	Description
read	✅	✅	Retrieves the value of the descriptor.
write	✅	✅	Writes the value of the descriptor.
onValueReceived	✅	✅	Stream of descriptor value changes
lastValueStream	✅	✅	Stream of lastValue + descriptor value changes

Throwing functions

All functions in FlutterBluePlus will throw exceptions when they encounter errors.

You MUST handle exceptions for bluetooth communication:

• BluetoothDevice.connect()
• BluetoothDevice.disconnect()
• BluetoothDevice.discoverServices()
• BluetoothDevice.requestMtu()
• BluetoothDevice.readRssi()
• BluetoothDevice.pair()
• BluetoothCharacteristic.read()
• BluetoothCharacteristic.write()
• BluetoothCharacteristic.setNotifyValue()
• BluetoothDescriptor.read()
• BluetoothDescriptor.read()

These functions also THROW:

• FlutterBluePlus.turnOn()
• FlutterBluePlus.turnOff()
• FlutterBluePlus.startScan()
• FlutterBluePlus.stopScan()
• FlutterBluePlus.scan()
• `BluetoothDevice.requestConnectionPriority
• BluetoothDevice.mtu
• BluetoothDevice.removeBond()
• BluetoothDevice.clearGattCache()
• BluetoothDevice.services
• BluetoothDevices.mtu

At the time of writing, these function DO NOT throw exceptions

• FlutterBluePlus.isAvailable
• FlutterBluePlus.isOn
• FlutterBluePlus.adapterState
• FlutterBluePlus.isScanning
• FlutterBluePlus.isScanningNow
• FlutterBluePlus.scanResults
• FlutterBluePlus.setLogLevel()
• BluetoothDevice.localName
• BluetoothDevice.connectionState
• BluetoothDevice.setPreferredPhy()
• BluetoothCharacteristic.isNotifying
• BluetoothCharacteristic.lastValue, uuid, & other simple accessors
• BluetoothDescriptor.lastValue, uuid, & other simple accessors

Streams

All of the Bluetooth receive streams NEVER emit errors and NEVER close. They only emit on success. These include:

• BluetoothCharacteristic.onValueReceived
• BluetoothCharacteristic.lastValueStream
• BluetoothDescriptor.onValueReceived
• BluetoothDescriptor.lastValueStream

You can listen to BluetoothDevice.connectionState to know when to stop listening.

These streams also NEVER emit any errors of any kind.

• FlutterBluePlus.isScanning
• FlutterBluePlus.scanResults
• FlutterBluePlus.adapterState
• BluetoothDevice.connectionState
• BluetoothDevice.isDiscoveringServices
• BluetoothDevice.services (only throws on first call if remoteId is invalid)
• BluetoothDevices.mtu (only throws on first call if remoteId is invalid)

Troubleshooting

The easiest way to debug issues in FlutterBluePlus is to first make local copy.

cd /user/downloads
git clone https://github.com/boskokg/flutter_blue_plus.git

then in pubspec.yaml add the repo by path:

  flutter_blue_plus:
    path: /user/downloads/flutter_blue_plus

Now you can edit FlutterBluePlus code and debug issues yourself.

When I scan using a service UUID filter, it doesn't find any devices.

Make sure the device is advertising which service UUID's it supports. This is found in the advertisement packet as UUID 16 bit complete list or UUID 128 bit complete list.