Shared Preferences Simple

 import "package:flutter/material.dart";

import "package:shared_preferences/shared_preferences.dart";

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Hello Flutter ",
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.brown,
      ),
      home: const FlutterShared(),
    );
  }
}

class FlutterShared extends StatefulWidget {
  const FlutterShared({super.key});

  @override
  State<FlutterShared> createState() {
    return SharedState();
  }
}

class SharedState extends State<FlutterShared> {
  var nameController = TextEditingController();

  //static const String KEYNAME = "name";

  var nameValue = "No Value Saved";

//initState() function can never handle asynchronously.we can never write "async" to initState() function
  @override
  void initState() {
    super.initState();
    getValue();
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        FocusManager.instance.primaryFocus?.unfocus();
      },
      child: Scaffold(
        drawer: const Drawer(),
        appBar: AppBar(
          title: const Text(
            "Flutter Shared preferences",
            style: TextStyle(fontWeight: FontWeight.bold),
          ),
          centerTitle: true,
          backgroundColor: Colors.grey,
        ),
        body: Container(
          child: Center(
            child: SizedBox(
              width: 200,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  TextField(
                    controller: nameController,
                    decoration: InputDecoration(
                      hintText: "Enter Name...",
                      label: const Text("Name"),
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(12),
                        borderSide: const BorderSide(
                          width: 2,
                        ),
                      ),
                    ),
                  ),
                  const SizedBox(
                    height: 40,
                  ),
                  ElevatedButton(
                    onPressed: () async {
                      print("1"); //for checking execution

                      var name = nameController.text.toString();

                      var prefs = await SharedPreferences.getInstance();

                      ///Any task which return in "Future" class then that task should be handled asynchronously
                      /// so that UI part will not be on hold Any function or class which take indefinite time to execute
                      /// then that function/class will be handled through "await" and will make asynchronous

                      prefs.setString("name", name);
                    },
                    style: ElevatedButton.styleFrom(
                      backgroundColor: Colors.blue,
                      fixedSize: const Size(350.0, 50.0),
                    ),
                    child: const Text(
                      "Save",
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          color: Colors.white,
                          fontSize: 20.0),
                    ),
                  ),
                  const SizedBox(
                    height: 40,
                  ),
                  Text(nameValue),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  void getValue() async {
    var prefs = await SharedPreferences.getInstance();

    var getName = prefs.getString("name");

    nameValue = getName != null ? getName : "No Value Saved";

    ///nameValue = getName ?? "No Value Saved";

    setState(() {});
  }
}