[UI - Hack] Circular loading of an image

main.dart

import 'dart:async';

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

Color get _backgroundColor => Colors.white;
int _index = 5;

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        backgroundColor: _backgroundColor,
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  late Timer _timer;
  @override
  initState() {
    super.initState();
    _timer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (!mounted) return;
      setState(() {
        _index--;
        print('_index: $_index');
        if (_index == 0) {
          _timer.cancel();
          _index = 5;
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        Positioned.fill(
          child: Center(
            child: Container(
              height: 150,
              width: 150,
              decoration: BoxDecoration(
//                 color: Colors.red,
                borderRadius: BorderRadius.circular(75),
                image: DecorationImage(
                  image: NetworkImage( 'https://media.istockphoto.com/vectors/pie-icon-on-white-round-vector-button-vector-id520295912?s=612x612'),
                ),
              ),
            ),
          ),
        ),
        Positioned.fill(
          child: Center(
            child: SizedBox(
              height: 150,
              width: 150,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  Row(
                    children: [
                      _index > 4
                          ? Container(
                              color: _backgroundColor,
                              height: 75,
                              width: 75,
                            )
                          : const SizedBox(
                              height: 75,
                              width: 75,
                            ),
                      _index > 3
                          ? Container(
                              color: _backgroundColor,
                              height: 75,
                              width: 75,
                            )
                          : const SizedBox(
                              height: 75,
                              width: 75,
                            ),
                    ],
                  ),
                  Row(
                    children: [
                      _index > 1
                          ? Container(
                              color: _backgroundColor,
                              height: 75,
                              width: 75,
                            )
                          : const SizedBox(
                              height: 75,
                              width: 75,
                            ),
                      _index > 2
                          ? Container(
                              color: _backgroundColor,
                              height: 75,
                              width: 75,
                            )
                          : const SizedBox(
                              height: 75,
                              width: 75,
                            ),
                    ],
                  ),
                ],
              ),
            ),
          ),
        ),
      ],
    );
  }
}

Update image url if not working