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

pub package


FlutterBlue



Introduction #

FlutterBluePlus is a bluetooth plugin for Flutter, a new app SDK to help developers build modern multi-platform apps. Note: this plugin is continuous work from FlutterBlue since maintaince stoped.

Alpha version #

This package must be tested on a real device.

Cross-Platform Bluetooth LE #

FlutterBluePlus aims to offer the most from both platforms (iOS and Android).

Using the FlutterBluePlus instance, you can scan for and connect to nearby devices (BluetoothDevice). Once connected to a device, the BluetoothDevice object can discover services (BluetoothService), characteristics (BluetoothCharacteristic), and descriptors (BluetoothDescriptor). The BluetoothDevice object is then used to directly interact with characteristics and descriptors.

Usage #

Obtain an instance #

FlutterBluePlus flutterBlue = FlutterBluePlus.instance;

Scan for devices #

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

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

// Stop scanning
flutterBlue.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.value.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)

Request connection priority #

await device.requestConnectionPriority(connectionPriorityRequest: ConnectionPriority.high);

Only in Android you can send a connection priority update to the BLE device. The parameter priority is an enum that uses the same spec as the BluetoothGatt Android spec. Using highPerformance will increase battery usage but will speed up GATT operations. Be cautious when setting the priority when communicating with multiple devices because if you set high performance for all devices the effect of increasing the priority will be lower.

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

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.
state 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.
state Stream of state 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.

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.
value Stream of characteristic's value when changed.

BluetoothDescriptor API #

Android iOS Description
read Retrieves the value of the descriptor.
write Writes the value of the descriptor.

Troubleshooting #

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.

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

Repository (GitHub)
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Documentation

API reference

License

BSD-3-Clause (LICENSE)

Dependencies

collection, convert, flutter, meta, protobuf, rxdart

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