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Android BLE Library

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An Android library that solves a lot of Android's Bluetooth Low Energy problems. The BleManager class exposes high level API for connecting and communicating with Bluetooth LE peripherals. The API is clean and easy to read.

Features

BleManager class provides the following features:

  1. Connection, with automatic retries
  2. Service discovery
  3. Bonding (optional) and removing bond information (using reflections)
  4. Automatic handling of Service Changed indications
  5. Device initialization
  6. Asynchronous and synchronous BLE operations using queue
  7. Splitting and merging long packets when writing and reading characteristics and descriptors
  8. Requesting MTU and connection priority (on Android Lollipop or newer)
  9. Reading and setting preferred PHY (on Android Oreo or newer)
  10. Reading RSSI
  11. Refreshing device cache (using reflections)
  12. Reliable Write support
  13. Operation timeouts (for connect, disconnect and wait for notification requests)
  14. Error handling
  15. Logging
  16. GATT server (since version 2.2)

The library does not provide support for scanning for Bluetooth LE devices. For scanning, we recommend using Android Scanner Compat Library which brings almost all recent features, introduced in Lollipop and later, to the older platforms.

Version 2.3

New features added in version 2.3:

  1. :ble-ktx module added with support for coroutines and Flow.
    1. .suspend() methods added in Requests.
    2. asFlow() method added to ValueChangedCallback.
    3. Connection and bonding state available as Flow.
    4. New helper methods to get a BluetoothGattCharacteristic with given required properties and instance id added to BluetoothGattService.
  2. JsonMerger class added, which should help with use cases when a device sends a JSON file in multiple packets.
  3. :ble-livedata migrated to Java with some API changes, as sealed classes are no longer available.
  4. Support for new onServicesChanged() callback, added in API 31 (Android 12).
  5. Option to cancel pending Bluetooth LE connection using ConnectRequest.cancelPendingConnection().

When using coroutines use .suspend() method in Request, instead of enqueue() or await().

To register to notifications and indications (or incoming write requests for server) use

setNotificationCallback(characteristic)
   .merge(JsonMerger()) // Example of how to use JsonMerger, optional
   .asFlow()

This is still experimental feature and any feedback is welcome.

Version 2.2

New features added in version 2.2:

  1. GATT Server support. This includes setting up the local GATT server on the Android device, new requests for server operations:
    • wait for read,
    • wait for write,
    • send notification,
    • send indication,
    • set characteristic value,
    • set descriptor value.
  2. New conditional requests:
    • wait if,
    • wait until.
  3. BLE operations are no longer called from the main thread.
  4. There's a new option to set a handler for invoking callbacks. A handler can also be set per-callback.

Migration to version 2.2

Version 2.2 breaks some API known from version 2.1.1. Check out migration guide.

Importing

Maven Central

The library may be found on Maven Central repository. Add it to your project by adding the following dependency:

implementation 'no.nordicsemi.android:ble:2.3.0'

The last version not migrated to AndroidX is 2.0.5.

BLE library with Kotlin extension is available in:

implementation 'no.nordicsemi.android:ble-ktx:2.3.0'

To import the BLE library with set of parsers for common Bluetooth SIG characteristics, use:

implementation 'no.nordicsemi.android:ble-common:2.3.0'

For more information, read this.

An extension for easier integration with LiveData is available after adding:

implementation 'no.nordicsemi.android:ble-livedata:2.3.0'

This extension adds ObservableBleManager with state and bondingState properties, which notify about connection and bond state using androidx.lifecycle.LiveData.

As a library module

Clone this project and add ble module as a dependency to your project:

  1. In settings.gradle file add the following lines:
include ':ble'
project(':ble').projectDir = file('../Android-BLE-Library/ble')
  1. In app/build.gradle file add implementation project(':ble') inside dependencies.
  2. Sync project and build it.

You may do the same with other modules available in this project. Keep in mind, that ble-livedata module requires Kotlin, but no special changes are required in the app.

Setting up

The library uses Java 1.8 features. If you're using Android Studio below 4.2, make sure your build.gradle includes the following configuration:

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    // For Kotlin projects additionally:
    kotlinOptions {
        jvmTarget = "1.8"
    }

Usage

A BleManager instance is responsible for connecting and communicating with a single peripheral. Multiple manager instances are allowed. Extend BleManager with you manager where you define the high level device's API.

BleManager may be used in different ways:

  1. In a Service, for a single connection - see nRF Toolbox -> RSC profile,
  2. In a Service with multiple connections - see nRF Toolbox -> Proximity profile,
  3. From ViewModel's repo - see Architecture Components and nRF Blinky,
  4. As a singleton - not recommended, see nRF Toolbox -> HRM.

Please refer to the examples/ble-gatt-client folder for a project that illustrates the GATT server provided as a foreground service. There's a simple UI with a text field to update with the value of a characteristic that can be read and subscribed to. This characteristic also demands encryption as an illustration of best-practice.

You can run this client on one device and a complimenting server on another (see the next section).

Adding GATT Server support

Starting from version 2.2 you may now define and use the GATT server in the BLE Library.

Please refer to the examples/ble-gatt-server folder for a project that illustrates the GATT server provided as a foreground service. There's a simple UI with a text field to update the value of a characteristic that can be read and subscribed to. This characteristic also demands encryption as an illustration of best-practice.

More examples

Find the simple example here Android nRF Blinky.

For an example how to use it from an Activity or a Service, check the base Activity and Service classes in nRF Toolbox.

Version 1.x

The BLE library v 1.x is no longer supported. Please migrate to 2.x for bug fixing releases. Find it on version/1x branch.

A migration guide is available here.