No more renderflex error??

onboarding_screen.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:onboarding_ui/utilities/styles.dart';

class OnboardingScreen extends StatefulWidget {
  @override
  _OnboardingScreenState createState() => _OnboardingScreenState();
}

class _OnboardingScreenState extends State<OnboardingScreen> {
  final int _numPages = 3;
  final PageController _pageController = PageController(initialPage: 0);
  int _currentPage = 0;

  List<Widget> _buildPageIndicator() {
    List<Widget> list = [];
    for (int i = 0; i < _numPages; i++) {
      list.add(i == _currentPage ? _indicator(true) : _indicator(false));
    }
    return list;
  }

  Widget _indicator(bool isActive) {
    return AnimatedContainer(
      duration: Duration(milliseconds: 150),
      margin: EdgeInsets.symmetric(horizontal: 8.0),
      height: 8.0,
      width: isActive ? 24.0 : 16.0,
      decoration: BoxDecoration(
        color: isActive ? Colors.white : Color(0xFF7B51D3),
        borderRadius: BorderRadius.all(Radius.circular(12)),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: AnnotatedRegion<SystemUiOverlayStyle>(
        value: SystemUiOverlayStyle.light,
        child: Container(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              begin: Alignment.topCenter,
              end: Alignment.bottomCenter,
              stops: [0.1, 0.4, 0.7, 0.9],
              colors: [
                Color(0xFF3594DD),
                Color(0xFF4563DB),
                Color(0xFF5036D5),
                Color(0xFF5B16D0),
              ],
            ),
          ),
          child: Padding(
            padding: EdgeInsets.symmetric(vertical: 40.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                Container(
                  alignment: Alignment.centerRight,
                  child: FlatButton(
                    onPressed: () => print('Skip'),
                    child: Text(
                      'Skip',
                      style: TextStyle(
                        color: Colors.white,
                        fontSize: 20.0,
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: Container(
                    child: PageView(
                      physics: ClampingScrollPhysics(),
                      controller: _pageController,
                      onPageChanged: (int page) {
                        setState(() {
                          _currentPage = page;
                        });
                      },
                      children: <Widget>[
                        Padding(
                          padding: EdgeInsets.all(40.0),
                          child: Expanded(
                            child: Column(
                              crossAxisAlignment: CrossAxisAlignment.start,
                              children: <Widget>[
                                Center(
                                  child: Image(
                                    image: AssetImage(
                                      'assets/images/onboarding0.png',
                                    ),
                                    height: 300.0,
                                    width: 300.0,
                                  ),
                                ),
                                SizedBox(height: 30.0),
                                Text(
                                  'Connect people\naround the world',
                                  style: kTitleStyle,
                                ),
                                SizedBox(height: 15.0),
                                Text(
                                  'Fareez ehhhhe',
                                  style: kSubtitleStyle,
                                ),
                              ],
                            ),
                          ),
                        ),
                        Padding(
                          padding: EdgeInsets.all(40.0),
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: <Widget>[
                              Image(
                                image: AssetImage(
                                  'assets/images/onboarding1.png',
                                ),
                                height: 300.0,
                                width: 300.0,
                              ),
                              SizedBox(height: 30.0),
                              Text(
                                'Live your life smarter\nwith us!',
                                style: kTitleStyle,
                              ),
                              SizedBox(height: 15.0),
                              Text(
                                'Lorem ipsum dololabore et.',
                                style: kSubtitleStyle,
                              ),
                            ],
                          ),
                        ),
                        Padding(
                          padding: EdgeInsets.all(40.0),
                          child: Expanded(
                            child: Column(
                              crossAxisAlignment: CrossAxisAlignment.start,
                              children: <Widget>[
                                Center(
                                  child: Image(
                                    image: AssetImage(
                                      'assets/images/onboarding2.png',
                                    ),
                                    height: 300.0,
                                    width: 300.0,
                                  ),
                                ),
                                SizedBox(height: 30.0),
                                Text(
                                  'Get a new experience\nof imagination',
                                  style: kTitleStyle,
                                ),
                                SizedBox(height: 15.0),
                                Text(
                                  'Lorem ipsum dolor sit amet, consect adipiscing elit, sed do eiusmod tempor incididunt ut labore et.',
                                  style: kSubtitleStyle,
                                ),
                              ],
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: _buildPageIndicator(),
                ),
                _currentPage != _numPages - 1
                    ? Align(
                        alignment: FractionalOffset.bottomRight,
                        child: FlatButton(
                          onPressed: () {
                            _pageController.nextPage(
                              duration: Duration(milliseconds: 500),
                              curve: Curves.ease,
                            );
                          },
                          child: Row(
                            mainAxisAlignment: MainAxisAlignment.center,
                            mainAxisSize: MainAxisSize.min,
                            children: <Widget>[
                              Text(
                                'Next',
                                style: TextStyle(
                                  color: Colors.white,
                                  fontSize: 22.0,
                                ),
                              ),
                              SizedBox(width: 10.0),
                              Icon(
                                Icons.arrow_forward,
                                color: Colors.white,
                                size: 30.0,
                              ),
                            ],
                          ),
                        ),
                      )
                    : Text(''),
              ],
            ),
          ),
        ),
      ),
      bottomSheet: _currentPage == _numPages - 1
          ? Container(
              height: 100.0,
              width: double.infinity,
              color: Colors.white,
              child: GestureDetector(
                onTap: () => print('Get started'),
                child: Center(
                  child: Padding(
                    padding: EdgeInsets.only(bottom: 30.0),
                    child: Text(
                      'Get started',
                      style: TextStyle(
                        color: Color(0xFF5B16D0),
                        fontSize: 20.0,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                  ),
                ),
              ),
            )
          : Text(''),
    );
  }
}