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androidbluetooth-lowenergyrxandroidble

Any way to monitor discovered BLE peripherals without connecting?

Is there any way of being notified if a discovered BLE peripheral moves out of range or otherwise drops out of sight? I'm using rxBleClient.scanBleDevices() to build a list of devices in the area that are advertising, but before shipping this list to the main application I'd like to be sure that all the devices are still reachable. What's the best way of doing this?

Solution

  • The vanilla Android Scan API allows for scanning BLE devices with callback types of:

    /**
 * A result callback is only triggered for the first advertisement packet received that matches
 * the filter criteria.
 */
public static final int CALLBACK_TYPE_FIRST_MATCH = 2;

/**
 * Receive a callback when advertisements are no longer received from a device that has been
 * previously reported by a first match callback.
 */
public static final int CALLBACK_TYPE_MATCH_LOST = 4;

    The same API is available via RxBleClient.scanBleDevices(ScanSettings, ScanFilter...)

    The CALLBACK_TYPE_FIRST_MATCH and CALLBACK_TYPE_MATCH_LOST are flags that can be put into ScanSettings.

    The timeout after which the CALLBACK_TYPE_MATCH_LOST is triggered is somewhere around 10 seconds. This may be an indication that a particular device is no longer in range/available.