isInstalled method

Implementation

@override
Future<bool?> isInstalled({Package package = Package.whatsapp}) async {
  String _package;
  _package = package.index == 0 ? "com.whatsapp" : "com.whatsapp.w4b";
  final bool? success = await methodChannel.invokeMethod<bool>(
    'isInstalled',
    <String, dynamic>{"package": _package},
  );
  return success;
}