How To Chain Multiple Animation Using Flutter App

import 'package:flutter/material.dart';
import 'dart:math';


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

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

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with SingleTickerProviderStateMixin {
  AnimationController animationController;
  Animation<double> opacityAnimation;
  Animation<double> rotationAnimation;
  Animation<double> sizeAnimation;

  @override
  void initState() {
    super.initState();
    animationController = AnimationController(
      vsync: this,
      duration: Duration(seconds: 5),
    );

    opacityAnimation = Tween<double>(
      begin: 0.0,
      end: 1.0,
    ).animate(CurvedAnimation(
      parent: animationController,
      curve: Interval(0.0, 0.3, curve: Curves.fastOutSlowIn),
    ));

    rotationAnimation = Tween<double>(
      begin: 0.0,
      end: pi * 4,
    ).animate(CurvedAnimation(
      parent: animationController,
      curve: Interval(0.3, 0.6, curve: Curves.ease),
    ));

    sizeAnimation = Tween<double>(
      begin: 70,
      end: 120,
    ).animate(CurvedAnimation(
      parent: animationController,
      curve: Interval(0.6, 1.0, curve: Curves.fastOutSlowIn),
    ));

    animationController.forward();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      appBar: AppBar(
        backgroundColor: Colors.green,
          title: Text("Chainig Multiple Animation")),
      body: Center(
        child: AnimatedBuilder(
          animation: animationController,
          builder: (context, child) {
            return Container(
              transform: Matrix4.identity()..rotateZ(rotationAnimation.value),
              child: Opacity(
                opacity: opacityAnimation.value,
                child: Container(
                  color: Colors.green,
                  height: sizeAnimation.value,
                  width: sizeAnimation.value,
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}