在flutter中滑动圆圈以打开新的活动(页面)

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

class CircleTransition extends StatefulWidget {
  @override
  _CircleTransitionState createState() => _CircleTransitionState();
}

class _CircleTransitionState extends State<CircleTransition>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: Duration(milliseconds: 500),
      vsync: this,
    );
    _animation = CurvedAnimation(
      parent: _controller,
      curve: Curves.easeInOut,
    );
    _controller.forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        Navigator.push(
          context,
          PageRouteBuilder(
            pageBuilder: (context, animation, secondaryAnimation) =>
                NewActivity(), // 替换为要打开的新活动（页面）的Widget
            transitionsBuilder:
                (context, animation, secondaryAnimation, child) {
              return ScaleTransition(
                scale: animation,
                child: child,
              );
            },
            transitionDuration: Duration(milliseconds: 500),
          ),
        );
      },
      child: AnimatedBuilder(
        animation: _animation,
        builder: (BuildContext context, Widget child) {
          return Container(
            width: _animation.value * 100,
            height: _animation.value * 100,
            decoration: BoxDecoration(
              shape: BoxShape.circle,
              color: Colors.blue,
            ),
            child: child,
          );
        },
        child: Icon(
          Icons.arrow_forward,
          color: Colors.white,
        ),
      ),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Center(
        child: CircleTransition(),
      ),
    );
  }
}