bluetooth

Bluetooth

This library provides support for out-of-the-box access to Bluetooth.

Installing

This library is available on Maven Central. You can import Kaluga Bluetooth as follows:

repositories {
    // ...
    mavenCentral()
}
// ...
dependencies {
    // ...
    implementation("com.splendo.kaluga:bluetooth:$kalugaVersion")
}

Usage

Create a Bluetooth object through the BluetoothBuilder. This gives you access to a Flow of Bluetooth devices. To scan for devices simply call

bluetooth.startScanning(setOf(someUUID))
launch {
    bluetooth.devices().collect {}
}
///
bluetooth.stopScanning()

Bluetooth Scanning is managed by a state machine that will keep running as long as it is observed. It will automatically handle Permissions and Enabling/Disabling bluetooth on the device, although this behaviour can be disabled via the BluetoothBuilder Devices are returned as a flow of Device objects, which manages the connection state of each device.

Devices can be grabbed via a getter method. This returns a flow on which the device can be connected/disconnected from. Services, Characteristics and Descriptors can be accessed via easy accessor methods.

launch {
    bluetooth.devices()[someUUID].advertisement().collect { advertisementData ->
        // handle Advertisement Data
    }   
}
// Connect to a device
bluetooth.devices()[someUUID].connect()

launch {
    bluetooth.devices()[someUUID].services()[serviceUUID].characteristics()[characteristicUUID].descriptors()[descriptorUUID].value().collect {
        // Observe value changes
    }
}

// Write data
bluetooth.devices()[someUUID].services()[serviceUUID].characteristics()[characteristicUUID].first().writeValue(newValue)

bluetooth.devices()[someUUID].disconnect()

Android

You may notice that when you ask for Kaluga's Permission.Bluetooth the android request alert will prompt Location permission. This behaviour is encountered because Android system requires Location to access the hardware identifiers of nearby external devices via Bluetooth.

Setup

In order to setup a bluetooth repo you need to create a Bluetooth object using a BluetoothBuilder.

class CommonViewModel(bltBuilder: BluetoothBuilder) : BaseLifecycleViewModel() {
    private val repo: Bluetooth = bltBuilder.create(
        scannerSettingsBuilder = { permissions ->
            BaseScanner.Settings(
                permissions = permissions,
                autoRequestPermission = false
            )
         },
        connectionSettings = ConnectionSettings(
            ConnectionSettings.ReconnectionSettings.Never
        )
    )
}

The BluetoothBuilder is created on the platform

Android

// Somewhere in Android code
val scanSettings = ScanSettings.Builder()
    .setScanMode(..)
    .setNumOfMatches(..)
    .build()

val scannerBuilder = DefaultScanner.Builder(scanSettings = scanSettings,..)

val bluetoothBuilder = BluetoothBuilder(
    scannerBuilder = scannerBuilder
)
CommonViewModel(bluetoothBuilder)

iOS

// Somewhere in iOS code
val scanSettings = ScanSettings(allowDuplicateKeys, solicitedServiceUUIDsKey)

val scannerBuilder = DefaultScanner.Builder(scanSettings)

val bluetoothBuilder = BluetoothBuilder(scannerBuilder = scannerBuilder)
CommonViewModel(bluetoothBuilder)

Notes

There is a major difference when it comes to the reporting of scanned devices between Android and iOS. Android report multiple scans of the same device, whereas iOS filters them out.

To align the behaviour across platforms the CBCentralManagerScanOptionAllowDuplicatesKey option is enabled on iOS. It can be set to another value using ScanSettings as shown above.

Testing

Use the test-utils-bluetooth module to get mockable Bluetooth classes.