How To Create Grid To Pager Using Flutter Android App

import 'package:flutter/material.dart';
void main(){
  runApp(MyApp());
}

class MyApp extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<String> images = [
    'img1.jpg',
    'img2.jpg',
    'img3.jpg',
    'img4.jpg',
    'img5.jpg',
    'img6.jpg',
    'img7.jpg',

  ];
  bool isPageViewVisible = false;

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: () async {
        if (isPageViewVisible) {
          _setPageViewVisible(false);
          return false;
        }
        return true;
      },
      child: Scaffold(
        backgroundColor: Colors.black,
        appBar: AppBar(
          backgroundColor: Colors.deepPurple,
            title: Text('Grid To Pager')),
        body: Stack(
          children: <Widget>[
            _buildGridView(),
            _buildPageView(),
          ],
        ),
      ),
    );
  }

  Widget _buildGridView() {
    return GridView.count(
      crossAxisCount: 2,
      children: images.map((imageName) {
        return GestureDetector(
          onTap: () => _setPageViewVisible(true), //<--- on GridView item click, show PageView
          child: Card(
            child: Center(
              child: Image.asset("assets/images/$imageName",),
            ),
          ),
        );
      }).toList(),
    );
  }

  Widget _buildPageView() {
    PageView pageView = PageView.builder(
      itemCount: images.length,
      itemBuilder: (context, index) {
        return Center(
          child: Image.asset("assets/images/${images[index]}"),
        );
      },
    );

    return Opacity(
      opacity: isPageViewVisible ? 1 : 0,
      child: IgnorePointer(
        ignoring: !isPageViewVisible,
        child: pageView,
      ),
    );
  }

  void _setPageViewVisible(bool visible) {
    setState(() => isPageViewVisible = visible);
  }
}