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  showDialogBox() => showCupertinoDialog<String>(
        context: context,
        builder: (BuildContext context) => CupertinoAlertDialog(
          title: const Text('No Connection'),
          content: const Text('Please check your internet connectivity'),
          actions: <Widget>[
            TextButton(
              onPressed: () async {
                Navigator.pop(context, 'Cancel');
                setState(() => isAlertSet = false);

vijayinyoutube

 late StreamSubscription subscription;
  bool isDeviceConnected = false;
  bool isAlertSet = false;

  @override
  void initState() {
    getConnectivity();
    super.initState();
  }

vijayinyoutube

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Connectivity Checker'),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () => Navigator.push(
            context,

vijayinyoutube

body: Center(
        child: ElevatedButton(
          onPressed: () async {
            await homePageData.saveJsonData(rawData);
            homePageData.getJsonData();
          },
          child: const Text('Save Data'),
        ),
      ),

vijayinyoutube

class HomePageData {
  Future saveJsonData(jsonData) async {
    final prefs = await SharedPreferences.getInstance();
    var saveData = jsonEncode(jsonData);
    await prefs.setString('jsonData', saveData);
  }

  Future<void> getJsonData() async {
    final prefs = await SharedPreferences.getInstance();
    var temp = prefs.getString('jsonData') ?? jsonEncode(defaultData);

vijayinyoutube

final rawData = <String, dynamic>{'name': 'Alice', 'age': 20};

final defaultData = <String, dynamic>{
  'name': 'name not found.',
  'age': 00,
};

vijayinyoutube

class HomePageModel {
  final String name;
  final int? age;

  HomePageModel(
    this.name,
    this.age,
  );

  

vijayinyoutube

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: ()  {},
          child: const Text('Save Data'),

vijayinyoutube

Future<void> _changeOpacity() async {
  setState(() => _visible = !_visible);
  await Future.delayed(const Duration(milliseconds: 650));
  setState(() => showPayBtn = !showPayBtn);
  setState(() => _visible = !_visible);
}

vijayinyoutube

 AnimatedOpacity(
  opacity: _visible ? 1.0 : 0.0,
  duration: const Duration(milliseconds: 650),
  child: ElevatedButton(
    ...
  ),
),