immich/mobile/lib/shared/views/immich_loading_overlay.dart

import 'package:flutter/material.dart';
import 'package:immich_mobile/shared/ui/immich_loading_indicator.dart';

class ImmichLoadingOverlay extends StatelessWidget {
  const ImmichLoadingOverlay({
    Key? key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<bool>(
      valueListenable: ImmichLoadingOverlayController.appLoader.loaderShowingNotifier,
      builder: (context, shouldShow, child) {
        if (shouldShow) {
          return const Scaffold(
            backgroundColor: Colors.black54,
            body: Center(
              child: ImmichLoadingIndicator(),
            ),
          );
        } else {
          return Container();
        }
      },
    );
  }
}

class ImmichLoadingOverlayController {
  static final ImmichLoadingOverlayController appLoader = ImmichLoadingOverlayController();
  ValueNotifier<bool> loaderShowingNotifier = ValueNotifier(false);
  ValueNotifier<String> loaderTextNotifier = ValueNotifier('error message');

  void show() {
    loaderShowingNotifier.value = true;
  }

  void hide() {
    loaderShowingNotifier.value = false;
  }
}