A code snippet to search through a list and return result from another page.

search_and_pop_result.dart

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'Flutter Demo',
        theme: ThemeData(
            primarySwatch: Colors.blue,
            appBarTheme: const AppBarTheme(
              backgroundColor: Colors.transparent,
              elevation: 0,
            )),
        home: Page1());
  }
}

class Page1 extends StatefulWidget {
  const Page1({Key? key}) : super(key: key);

  @override
  State<Page1> createState() => _Page1State();
}

class _Page1State extends State<Page1> {
  final controller = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text('Enter name of your country'),
            const SizedBox(height: 8),
            TextField(
              readOnly: true,
              onTap: () async {
                final result = await Navigator.of(context)
                    .push(MaterialPageRoute(builder: (ctx) => Page2()));
                if (result == null) return;
                setState(() => controller.text = result);
              },
              controller: controller,
              decoration: const InputDecoration(
                  focusedBorder: OutlineInputBorder(),
                  hintText: 'E.g: Ghana',
                  enabledBorder: OutlineInputBorder()),
            )
          ],
        ),
      ),
    );
  }
}

class Page2 extends StatefulWidget {
  const Page2({Key? key}) : super(key: key);

  @override
  State<Page2> createState() => _Page2State();
}

class _Page2State extends State<Page2> {
  final controller = TextEditingController();
  List<String> countries = [
    'Nigeria',
    'Ghana',
    'Liberia',
    'South Africa',
    'Kenya'
  ];
  List<String> searchTerm = [];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: [
            const SizedBox(height: 35),
            TextField(
              onChanged: (val) {
                setState(() {
                  searchTerm = countries
                      .where((element) =>
                          element.toLowerCase().contains(val.toLowerCase()))
                      .toList();
                });
              },
              controller: controller,
              decoration: const InputDecoration(
                  focusedBorder: OutlineInputBorder(),
                  hintText: 'E.g: Ghana',
                  enabledBorder: OutlineInputBorder()),
            ),
            Expanded(
                child: ListView(
              children: List.generate(
                  searchTerm.length,
                  (i) => ListTile(
                        onTap: () => Navigator.of(context).pop(searchTerm[i]),
                        title: Text(searchTerm[i]),
                      )),
            ))
          ],
        ),
      ),
    );
  }
}