dispose method
void
dispose()
Implementation
void dispose() {
_userPaused = true;
_lifecyclePaused = false;
_pendingInitialStart = false;
_resumeWaitCompleter?.complete();
_resumeWaitCompleter = null;
_lifecycleListener?.dispose();
_lifecycleListener = null;
_cancelTimers();
_barcodeSubscription?.cancel();
_barcodeSubscription = null;
unawaited(_scanner.stop());
unawaited(_scanController.close());
unawaited(_stateChanges.close());
}