Show button in the last item of a welcomescreen

I have a problem. I want to show a welcomescreen, with different screen. And when the last screen is shown the button should be also shown. So that the user jumps from welcomescreen to the secondscreen. How can I do this?

In my code it does not regoncie the context and I don't know how I could create the if condition.

WelcomeScreen.dart

import 'package:flutter/material.dart';
import '/items.dart';
import '/SecondRoute.dart';

class WelcomeScreen extends StatefulWidget {
  @override
  _WelcomeScreenState createState() => _WelcomeScreenState();
}

class _WelcomeScreenState extends State<WelcomeScreen> {
  List<Widget> slides = items
      .map((item) => Container(
      padding: EdgeInsets.symmetric(horizontal: 18.0),
      child: Column(
        children: <Widget>[
          Flexible(
            flex: 1,
            fit: FlexFit.tight,
            child: Image.asset(
              item['image'],
              fit: BoxFit.fitWidth,
              width: 220.0,
              alignment: Alignment.bottomCenter,
            ),
          ),
          Flexible(
            flex: 1,
            fit: FlexFit.tight,
            child: Container(
              padding: EdgeInsets.symmetric(horizontal: 30.0),
              child: Column(
                children: <Widget>[
                  Text(item['header'],
                      style: TextStyle(
                          fontSize: 50.0,
                          fontWeight: FontWeight.w300,
                          color: Color(0XFF3F3D56),
                          height: 2.0)),
                  Text(
                    item['description'],
                    style: TextStyle(
                        color: Colors.grey,
                        letterSpacing: 1.2,
                        fontSize: 16.0,
                        height: 1.3),
                    textAlign: TextAlign.center,
                  ),
                  if (true)
                    ElevatedButton(
                      child: const Text('Open route'),
                      onPressed: () {
                        Navigator.push(
                          context,
                          MaterialPageRoute(builder: (context) => const SecondRoute()),
                        );
                      },
                    ),
                ],
              ),
            ),
          )
        ],
      )))
      .toList();

  List<Widget> indicator() => List<Widget>.generate(
      slides.length,
          (index) => Container(
        margin: EdgeInsets.symmetric(horizontal: 3.0),
        height: 10.0,
        width: 10.0,
        decoration: BoxDecoration(
            color: currentPage.round() == index
                ? Color(0XFF256075)
                : Color(0XFF256075).withOpacity(0.2),
            borderRadius: BorderRadius.circular(10.0)),
      ));

  double currentPage = 0.0;
  final _pageViewController = new PageController();

  @override
  void initState() {
    super.initState();
    _pageViewController.addListener(() {
      setState(() {
        currentPage = _pageViewController.page!;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: Stack(
          children: <Widget>[
            PageView.builder(
              controller: _pageViewController,
              itemCount: slides.length,
              itemBuilder: (BuildContext context, int index) {
                return slides[index];
              },
            ),
            Align(
                alignment: Alignment.bottomCenter,
                child: Container(
                  margin: EdgeInsets.only(top: 70.0),
                  padding: EdgeInsets.symmetric(vertical: 40.0),
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: indicator(),
                  ),
                )
              //  ),
            )
            // )
          ],
        ),
      ),
    );
  }
}

items.dart

List items = [
  {
    "header": "Learn",
    "description":
    "Online chat which provides its users maximum functionality to simplify the search",
    "image": "assets/images/2.png"
  },
  {
    "header": "Build",
    "description":
    "Online chat which provides its users maximum functionality to simplify the search",
    "image": "assets/images/3.png"
  },
  {
    "header": "Launch",
    "description":
    "Online chat which provides its users maximum functionality to simplify the search",
    "image": "assets/images/1.png"
  },
  {
    "header": "Invest",
    "description":
    "Online chat which provides its users maximum functionality to simplify the search",
    "image": "assets/images/5.png"
  },
  {
    "header": "Travel",
    "description":
    "Online chat which provides its users maximum functionality to simplify the search",
    "image": "assets/images/4.png",
    "button": "true",
  }
];

You just have to check if the item contains the button key and display the button accordingly

            if (item.containsKey('button') && item['button'] == 'true')
ElevatedButton(
child: const Text('Open route'),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => const SecondRoute()),
);
},
),

For the new issue you are getting
The instance member 'context' can't be accessed in an initializer.,

Change the pageview to use the items.

PageView.builder(
itemCount: items.length,
itemBuilder: (BuildContext context, int index) {
return slide(items[index]);
},
),

Then update the initialized list of slides to the custom widget to access the context.

Update the slides from

List<Widget> slides = items
.map((item) => Container(
padding: EdgeInsets.symmetric(horizontal: 18.0),

to

Widget slide(Map<String, dynamic> item) {
return Container(
padding: EdgeInsets.symmetric(horizontal: 18.0),
child: Column(
children: <Widget>[

Full code in dartpad.dev.