wave animation

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: OnBoarding(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('Hello, World!', style: Theme.of(context).textTheme.display1);
  }
}


class OnBoarding extends StatefulWidget {
  @override
  _OnBoardingState createState() => new _OnBoardingState();
}

class _OnBoardingState extends State<OnBoarding> with TickerProviderStateMixin {
  PageController _controller;
  int currentPage = 0;
  bool lastPage = false;
  AnimationController animationController;
  Animation<double> _scaleAnimation;

  @override
  void initState() {
    super.initState();
    _controller = PageController(
      initialPage: currentPage,
    );
    animationController =
        AnimationController(duration: Duration(milliseconds: 400), vsync: this);
    _scaleAnimation = Tween(begin: 0.6, end: 1.0).animate(animationController);
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      decoration: BoxDecoration(
        gradient: LinearGradient(
            colors: [
              Colors.black87,
              Colors.blueGrey,
            ],
            tileMode: TileMode.repeated,
            begin: Alignment.topRight,
            stops: [0.0, 1.0],
            end: Alignment.bottomCenter),
      ),
      child: Scaffold(
        backgroundColor: Colors.transparent,
        body: new Stack(
          fit: StackFit.expand,
          children: <Widget>[
            PageView.builder(
              itemCount: pageList.length,
              controller: _controller,
              onPageChanged: (index) {
                setState(() {
                  currentPage = index;
                  if (currentPage == pageList.length - 1) {
                    lastPage = true;
                    animationController.forward();
                  } else {
                    lastPage = false;
                    animationController.reset();
                  }
                  print(lastPage);
                });
              },
              itemBuilder: (context, index) {
                return AnimatedBuilder(
                  animation: _controller,
                  builder: (context, child) {
                    var page = pageList[index];
                    var delta;
                    var y = 1.0;

                    if (_controller.position.haveDimensions) {
                      delta = _controller.page - index;
                      y = 1 - delta.abs().clamp(0.0, 1.0);
                    }
                    return Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.start,
                      mainAxisSize: MainAxisSize.min,
                      children: <Widget>[
                        Image.asset(
                          page.imageUrl,
                          height: 60,
                        ),
                        Container(
                          margin: EdgeInsets.only(left: 12.0),
                          height: 100.0,
                          child: Stack(
                            children: <Widget>[
                              Opacity(
                                opacity: .39,
                                child: Text("hello")
                              ),
                              Padding(
                                padding: EdgeInsets.only(top: 18.0, left: 22.0),
                                child: Text("hello")
                              ),
                            ],
                          ),
                        ),
                        Padding(
                          padding: const EdgeInsets.only(
                              left: 34.0, top: 12.0, right: 8),
                          child: Transform(
                            transform:
                                Matrix4.translationValues(0, 50.0 * (1 - y), 0),
                            child: Text(
                              page.body,
                              style: TextStyle(
                                  fontSize: 18.0,
                                  fontFamily: "Montserrat-Medium",
                                  color: Colors.white),
                            ),
                          ),
                        )
                      ],
                    );
                  },
                );
              },
            ),
            Positioned(
              left: 30.0,
              bottom: 55.0,
              child: Container(
                  width: 160.0,
                  child: PageIndicator(currentPage, pageList.length)),
            ),
            Positioned(
              right: 30.0,
              bottom: 30.0,
              child: ScaleTransition(
                scale: _scaleAnimation,
                child: lastPage
                    ? FloatingActionButton.extended(
                        backgroundColor: Colors.white,
                        label: Text("login",
                            style: TextStyle(
                              color: Colors.blue,
                            )),
                        icon: Icon(
                          Icons.directions_boat,
                          color: Colors.blueAccent,
                        ),
                        onPressed: () {
                          Navigator.pushReplacementNamed(context, '/welcome');
                        },
                      )
                    : Container(),
              ),
            ),
          ],
        ),
      ),
    );
}
}
  
  
var pageList = [
  PageModel(
      imageUrl: "assets/c.png",
      title: "name",
      body: "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis  ",
      titleGradient: gradients[0]),
 
  PageModel(
      imageUrl: "assets/ai.png",
      title: "Get quick assitance",
      body:
          "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis ",
      titleGradient: gradients[2]),
  PageModel(
      imageUrl: "assets/do.png",
      title: "Getting Started",
      body:
          " Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis  ",
      titleGradient: gradients[3]),
];

List<List<Color>> gradients = [
  [Color(0xFF00E676), Color(0xFF736EFE)],
  [Color(0xFF9708CC), Color(0xFF43CBFF)],
  [Color(0xFFE2859F), Color(0xFFFCCF31)],
  [Color(0xFF43CBFF), Color(0xFF736EFE)],
];

class PageModel {
  var imageUrl;
  var title;
  var body;
  List<Color> titleGradient = [];
  PageModel({this.imageUrl, this.title, this.body, this.titleGradient});
}
 
  
class PageIndicator extends StatelessWidget {
  final int currentIndex;
  final int pageCount;
  PageIndicator(this.currentIndex, this.pageCount);

  _indicator(bool isActive) {
    return Expanded(
      child: Padding(
        padding: EdgeInsets.symmetric(horizontal: 4.0),
        child: Container(
          height: 4.0,
          decoration: BoxDecoration(
              color: isActive ? Colors.white : Colors.blueGrey,
              boxShadow: [
                BoxShadow(
                    color: Colors.black12,
                    offset: Offset(0.0, 2.0),
                    blurRadius: 2.0)
              ]),
        ),
      ),
    );
  }

  _buildPageIndicators() {
    List<Widget> indicatorList = [];
    for (int i = 0; i < pageCount; i++) {
      indicatorList
          .add(i == currentIndex ? _indicator(true) : _indicator(false));
    }
    return indicatorList;
  }

  @override
  Widget build(BuildContext context) {
    return new Row(
      children: _buildPageIndicators(),
    );
  }
}