Read multiple characteristics from an Android device using library RxAndroidBle - bluetooth-lowenergy

Question

I am using the library RxAndroidBle in order to scan devices and then connect to one specific device and read 4 GATT characteristics.
I can read one characteristic (Battery Level) ith this code :
scanSubscription = rxBleClient.scanBleDevices(
new ScanSettings.Builder()
.build()
)
.observeOn(AndroidSchedulers.mainThread())
.doOnNext(
scanResult -> {
if(scanResult.getBleDevice().getName() != null){
if(scanResult.getBleDevice().getName().equals("NODE 1")){
Log.e("BLE SCAN", "SUCCESS");
Log.e("BLE SCAN", scanResult.getBleDevice().getName());
Log.e("BLE SCAN", scanResult.getBleDevice().getMacAddress());
scanSubscription.unsubscribe();
RxBleDevice device = scanResult.getBleDevice();
subscription = device.establishConnection(false) // <-- autoConnect flag
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(UUID.fromString("00002a19-0000-1000-8000-00805f9b34fb")))
.subscribe(
characteristicValue -> {
Log.e("Characteristic", characteristicValue[0]+"");
},
throwable -> {
Log.e("Error", throwable.getMessage());
}
);
}
}
}
)
.subscribe();
I can read two by using :
.flatMap(rxBleConnection -> Observable.combineLatest( // use the same connection and combine latest emissions
rxBleConnection.readCharacteristic(aUUID),
rxBleConnection.readCharacteristic(bUUID),
Pair::new
))
But I don't understand how to do that with 4 characteristics for example.
Thank you

Answer 1

The above example is just fine you would only need some data object that would accept more values than Pair. For instance something like:
class ReadResult {
final byte[] aValue;
final byte[] bValue;
final byte[] cValue;
final byte[] dValue;
ReadResult(byte[] aValue, byte[] bValue, byte[] cValue, byte[] dValue) {
this.aValue = aValue;
this.bValue = bValue;
this.cValue = cValue;
this.dValue = dValue;
}
}
And then the example could look like this:
disposable = rxBleClient.scanBleDevices(
new ScanSettings.Builder().build(),
new ScanFilter.Builder().setDeviceName("NODE 1").build() // one can set filtering by name here
)
.take(1) // take only the first result and then the upstream will get unsubscribed (scan will end)
.flatMap(scanResult -> scanResult.getBleDevice().establishConnection(false)) // connect to the first scanned device that matches the filter
.flatMapSingle(rxBleConnection -> Single.zip( // once connected read all needed values
rxBleConnection.readCharacteristic(aUUID),
rxBleConnection.readCharacteristic(bUUID),
rxBleConnection.readCharacteristic(cUUID),
rxBleConnection.readCharacteristic(dUUID),
ReadResult::new // merge them into a single result
))
.take(1) // once the result of all reads is available unsubscribe from the upstream (connection will end)
.subscribe(
readResult -> Log.d("Characteristics", /* print the readResult */),
throwable -> Log.e("Error", throwable.getMessage())
);
Original/Legacy solution for RxAndroidBle based on RxJava1:
subscription = rxBleClient.scanBleDevices(
new ScanSettings.Builder().build(),
new ScanFilter.Builder().setDeviceName("NODE 1").build() // one can set filtering by name here
)
.take(1) // take only the first result and then the upstream will get unsubscribed (scan will end)
.flatMap(scanResult -> scanResult.getBleDevice().establishConnection(false)) // connect to the first scanned device that matches the filter
.flatMap(rxBleConnection -> Observable.combineLatest( // once connected read all needed values
rxBleConnection.readCharacteristic(aUUID),
rxBleConnection.readCharacteristic(bUUID),
rxBleConnection.readCharacteristic(cUUID),
rxBleConnection.readCharacteristic(dUUID),
ReadResult::new // merge them into a single result
))
.take(1) // once the result of all reads is available unsubscribe from the upstream (connection will end)
.subscribe(
readResult -> Log.d("Characteristics", /* print the readResult */),
throwable -> Log.e("Error", throwable.getMessage())
);