//From Flutter
Future<String> _getBatteryLevel() async {
    String batteryLevel;
    try {
      //invoke the platform specific code
      //wait for the result
      final int result = await platform.invokeMethod('getBatteryLevel');
      batteryLevel = 'Battery level at $result % .';
    } on PlatformException catch (e) {
      batteryLevel = "Failed to get battery level: '${e.message}'.";
    }

    return batteryLevel;
}