如何在flutter中制作截图动画？

import 'package:flutter/material.dart';
import 'package:screenshot/screenshot.dart';
import 'package:flutter_sequence_animation/flutter_sequence_animation.dart';

class ScreenshotAnimation extends StatefulWidget {
  @override
  _ScreenshotAnimationState createState() => _ScreenshotAnimationState();
}

class _ScreenshotAnimationState extends State<ScreenshotAnimation>
    with SingleTickerProviderStateMixin {
  ScreenshotController screenshotController = ScreenshotController();
  AnimationController _animationController;
  SequenceAnimation sequenceAnimation;

  @override
  void initState() {
    super.initState();
    _animationController = AnimationController(
      vsync: this,
      duration: Duration(seconds: 2),
    );

    sequenceAnimation = SequenceAnimationBuilder()
        .addAnimatable(
          animatable: Tween<double>(begin: 0, end: 1),
          from: Duration(seconds: 0),
          to: Duration(seconds: 1),
          tag: "opacity",
        )
        .addAnimatable(
          animatable: Tween<double>(begin: 0, end: 100),
          from: Duration(seconds: 0),
          to: Duration(seconds: 1),
          tag: "translate",
        )
        .animate(_animationController);
  }

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

  void _startAnimation() {
    _animationController.reset();
    _animationController.forward();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Screenshot Animation'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Screenshot(
              controller: screenshotController,
              child: Container(
                width: 200,
                height: 200,
                color: Colors.blue,
              ),
            ),
            SizedBox(height: 20),
            AnimatedBuilder(
              animation: _animationController,
              builder: (context, child) {
                return Opacity(
                  opacity: sequenceAnimation['opacity'].value,
                  child: Transform.translate(
                    offset: Offset(
                      0,
                      -sequenceAnimation['translate'].value,
                    ),
                    child: Screenshot(
                      controller: screenshotController,
                      child: Container(
                        width: 200,
                        height: 200,
                        color: Colors.red,
                      ),
                    ),
                  ),
                );
              },
            ),
            SizedBox(height: 20),
            RaisedButton(
              onPressed: _startAnimation,
              child: Text('Start Animation'),
            ),
          ],
        ),
      ),
    );
  }
}