in controller

Define variables

                      final List<Map<String, dynamic>> allPlayers = [
                        {"name": "Rohit Sharma", "country": "India"},
                        {"name": "Virat Kohli ", "country": "India"},
                        {"name": "Glenn Maxwell", "country": "Australia"},
                        {"name": "Aaron Finch", "country": "Australia"},
                        {"name": "Martin Guptill", "country": "New Zealand"},
                        {"name": "Trent Boult", "country": "New Zealand"},
                        {"name": "David Miller", "country": "South Africa"},
                        {"name": "Kagiso Rabada", "country": "South Africa"},
                        {"name": "Chris Gayle", "country": "West Indies"},
                        {"name": "Jason Holder", "country": "West Indies"},
                      ];
                      Rx<List<Map<String, dynamic>>> foundPlayers =
                      Rx<List<Map<String, dynamic>>>([]);

                    

Function

                    @override
  void onInit() {
    super.onInit();
    foundPlayers.value = allPlayers;
  }

  @override
  void onReady() {
    super.onReady();
  }

  @override
  void onClose() {}
  void filterPlayer(String playerName) {
    List<Map<String, dynamic>> results = [];
    if (playerName.isEmpty) {
      results = allPlayers;
    } else {
      results = allPlayers
          .where((element) => element["name"]
          .toString()
          .toLowerCase()
          .contains(playerName.toLowerCase()))
          .toList();
    }
    foundPlayers.value = results;
  }

Complete code

import 'package:get/get.dart';

import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:vera/models/user_model.dart';




class FilterController extends GetxController {

  final List<Map<String, dynamic>> allPlayers = [
    {"name": "Rohit Sharma", "country": "India"},
    {"name": "Virat Kohli ", "country": "India"},
    {"name": "Glenn Maxwell", "country": "Australia"},
    {"name": "Aaron Finch", "country": "Australia"},
    {"name": "Martin Guptill", "country": "New Zealand"},
    {"name": "Trent Boult", "country": "New Zealand"},
    {"name": "David Miller", "country": "South Africa"},
    {"name": "Kagiso Rabada", "country": "South Africa"},
    {"name": "Chris Gayle", "country": "West Indies"},
    {"name": "Jason Holder", "country": "West Indies"},
  ];
  Rx<List<Map<String, dynamic>>> foundPlayers =
  Rx<List<Map<String, dynamic>>>([]);

  @override
  void onInit() {
    super.onInit();
    foundPlayers.value = allPlayers;
  }

  @override
  void onReady() {
    super.onReady();
  }

  @override
  void onClose() {}
  void filterPlayer(String playerName) {
    List<Map<String, dynamic>> results = [];
    if (playerName.isEmpty) {
      results = allPlayers;
    } else {
      results = allPlayers
          .where((element) => element["name"]
          .toString()
          .toLowerCase()
          .contains(playerName.toLowerCase()))
          .toList();
    }
    foundPlayers.value = results;
  }


}

in view

Serach panel

        Padding(
          padding: const EdgeInsets.all(25),
          child: TextField(
            onChanged: (value) => controller.filterPlayer(value),
            decoration: const InputDecoration(
              labelText: 'Search',
              suffixIcon: Icon(Icons.search),
            ),
          ),
        ),

      

Listview

Expanded(
                    child: Obx(
                          () => ListView.builder(
                        itemCount: controller.foundPlayers.value.length,
                        itemBuilder: (context, index) => ListTile(
                          title: Text(
                            controller.foundPlayers.value[index]['name'],
                            style:
                            TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
                          ),
                          subtitle:
                          Text(controller.foundPlayers.value[index]['country']),
                        ),
                      ),
                    ),
                  ),

                

Complete code

                import 'package:flutter/material.dart';
import 'package:vera/controllers/filter_controller.dart';
import 'package:get/get.dart';
import 'package:vera/models/user_model.dart';
import 'package:vera/widgets/bottom_nav.dart';

class LoginPage extends StatelessWidget {
  @override

  final FilterController controller = Get.put(FilterController());

  

  Widget build(BuildContext context) {
    //List<UserModel> userList = controller.userList;


    return GetBuilder<FilterController>(
        builder: (controller) => Scaffold(

            body: Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [

                  Padding(
                    padding: const EdgeInsets.all(25),
                    child: TextField(
                      onChanged: (value) => controller.filterPlayer(value),
                      decoration: const InputDecoration(
                        labelText: 'Search',
                        suffixIcon: Icon(Icons.search),
                      ),
                    ),
                  ),



                  Expanded(
                    child: Obx(
                          () => ListView.builder(
                        itemCount: controller.foundPlayers.value.length,
                        itemBuilder: (context, index) => ListTile(
                          title: Text(
                            controller.foundPlayers.value[index]['name'],
                            style:
                            TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
                          ),
                          subtitle:
                          Text(controller.foundPlayers.value[index]['country']),
                        ),
                      ),
                    ),
                  ),

             
              
                ],
              ),
            ),
          //bottomNavigationBar:BottomNavBar()

        )
    );
  }
}