FlutterBleLib

A library for all your Bluetooth Low Energy needs in Flutter. Internally utilizes Polidea’s MultiPlatformBleAdapter, which runs on RxAndroidBle and RxBluetoothKit.

BLE Simulator

This library supports BLEmulator, the BLE simulator. The simulation allows one to develop without a physical smartphone or BLE peripheral and use one’s production BLE–related code in automated testing.

Usage

To use this plugin, add flutter_ble_lib as a dependency in your pubspec.yaml file.

Overview

The library is organized around a few base entities, which are:

• BleManager
• Peripheral
• Service
• Characteristic

You have to create an instance BleManager and initialize underlying native resources. Using that instance you then obtain an instance of Peripheral, which can be used to run operations on the corresponding peripheral.

All operations passing the Dart-native bridge are asynchronous, hence all operations in the plugin return either Future or Stream.

For more information, see REFERENCE.

Initialising

BleManager bleManager = BleManager();
bleManager.createClient(); //ready to go!
// your peripheral logic
bleManager.destroyClient(); //remember to release native resources when you're done!

Following snippets assume the library has been initialized.

Handling Bluetooth adapter state

enum BluetoothState {
  UNKNOWN,
  UNSUPPORTED,
  UNAUTHORIZED,
  POWERED_ON,
  POWERED_OFF,
  RESETTING,
}


bleManager.enableRadio(); //ANDROID-ONLY turns on BT. NOTE: doesn't check permissions
bleManager.disableRadio() //ANDROID-ONLY turns off BT. NOTE: doesn't check permissions
BluetoothState currentState = await bleManager.bluetoothState();
bleManager.observeBluetoothState().listen((btState) {
  print(btState);
  //do your BT logic, open different screen, etc.
});

Scanning for peripherals

bleManager.startPeripheralScan(
  uuids: [
    "F000AA00-0451-4000-B000-000000000000",
  ],
).listen((scanResult) {
  //Scan one peripheral and stop scanning
  print("Scanned Peripheral ${scanResult.peripheral.name}, RSSI ${scanResult.rssi}");
  bleManager.stopPeripheralScan();
});

The snippet above starts the peripheral scan and stops it after receiving the first result. It filters the scan results to those that advertise a service with specified UUID.

Connecting to peripheral

First you must obtain a ScanResult from BleManager.startPeripheralScan().

Peripheral peripheral = scanResult.peripheral;
peripheral.observeConnectionState(emitCurrentValue: true, completeOnDisconnect: true)
  .listen((connectionState) {
    print("Peripheral ${scanResult.peripheral.identifier} connection state is $connectionState");
  });
await peripheral.connect();
bool connected = await peripheral.isConnected();
await peripheral.disconnectOrCancelConnection();

The snippet above starts observing the state of the connection to the peripheral, connects to it, checks if it’s connected and then disconnects from it.

Transactions

Methods that do not have counterpart with opposite effect and are asynchronous accept String transactionId as an optional argument, to allow the user to cancel such an operation. The Future returned to Dart will then finish with a BleError(BleErrorCode.operationCancelled…), but this will only discard the result of the operation, the operation itself will be executed either way.

For example, if I decided that I no longer want to run discovery on the selected peripheral:

//assuming peripheral is connected
peripheral.discoverAllServicesAndCharacteristics(transactionId: "discovery"); 
//will return operation cancelled error after calling the below 
bleManager.cancelTransaction("discovery");

If no transactionId has been specified, it is null. Each new operation with the same transactionId will cause the previous to be canceled with an error if it hasn’t finished yet.

NOTE: null is a valid transactionId, which means every operation with default transactionId will cancel any ongoing operation with default transactionId.

Obtaining characteristics

To be able to operate on the peripheral, the discovery of its services and characteristics must be run first.

//assuming peripheral is connected
await peripheral.discoverAllServicesAndCharacteristics();
List<Service> services = await peripheral.services(); //getting all services
List<Characteristic> characteristics1 = await peripheral.characteristics("F000AA00-0451-4000-B000-000000000000");
List<Characteristic> characteristics2 = await services.firstWhere(
  (service) => service.uuid == "F000AA00-0451-4000-B000-000000000000").characteristics();

//characteristics1 and characteristics2 have the same contents

Objects representing characteristics have a unique identifier, so they point to one specific characteristic, even if there are multiple service/characteristic UUID matches.

Manipulating characteristics

Below are 3 methods of writing to a characteristic, which all result in the same effect given there’s only one service with specified UUID and only one characteristic with specified UUID.

peripheral.writeCharacteristic(
  "F000AA00-0451-4000-B000-000000000000",
  "F000AA02-0451-4000-B000-000000000000",
  Uint8List.fromList([0]),
  false); //returns Characteristic to chain operations more easily

service.writeCharacteristic(
  "F000AA02-0451-4000-B000-000000000000",
  Uint8List.fromList([0]),
  false); //returns Characteristic to chain operations more easily

characteristic.write(Uint8List.fromList([0]), false); //returns void

Monitoring or reading a characteristic from Peripheral/Service level return CharacteristicWithValue object, which is Characteristic with additional Uint8List value property.

Maintainers

TBD

License

Copyright 2019 Polidea Sp. z o.o

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Download Flutter BLE Library Source Code on GitHub

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