public final class CompanionDevices

Companion-device association: the OS-managed relationship between this app and one particular accessory.

Associating is not pairing. It is the app telling the operating system “this is my device”, through a chooser the OS draws and the user picks from, and getting back privileges that an ordinary Bluetooth scan does not carry:

• The OS watches for the device instead of the app. startObservingPresence asks the platform to wake the app when the accessory comes into range, which replaces a scan the app would otherwise run – and pay for in battery – forever.
• Scanning stops needing location permission. On Android, finding your own associated device is not the same question as finding out where the user is, and the platform treats it accordingly.
• The user sees one honest prompt naming one device, instead of a blanket “this app wants to find nearby devices”.

AssociationRequest req = new AssociationRequest.Builder()
        .addFilter(DeviceFilter.bleService("180D"))
        .build();
CompanionDevices.associate(req).onResult((device, err) -> {
    if (err == null) {
        Preferences.set("sensor", device.getId());
        CompanionDevices.startObservingPresence(device.getId());
    }
});

Platform support

• Android – CompanionDeviceManager, with presence observation.
• iOS – AccessorySetupKit, on iOS 18 and later. The picker returns an accessory the app may then talk to over com.codename1.bluetooth without holding the blanket Bluetooth authorization. Earlier iOS versions report isSupported() false; there the app scans with com.codename1.bluetooth as before.
• Simulator, desktop and JavaScript – a simulated association store reporting NearbyAvailability.LOCAL_ONLY.
• Every other port – unsupported, and every call fails fast.