Text Scroller without a CustomPainter

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
  AnimationController _animdationController;
  List<String> labels = ['First Label', 'Second Label'];

  @override
  void initState() {
    super.initState();
    _animdationController = AnimationController(
      duration: const Duration(seconds: 2),
      vsync: this,
    )
      ..addListener(() {
        setState(() {});
      })
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed) {
          labels = labels.reversed.toList();
          _animdationController.forward(from: 0);
        }
      })
      ..forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: Scaffold(
        backgroundColor: Colors.green,
        body: Center(
          child: Container(
            height: 20,
            child: ClipRRect(
              child: ShaderMask(
                shaderCallback: (Rect bounds) => LinearGradient(
                  begin: Alignment.topLeft,
                  end: Alignment.bottomLeft,
                  colors: <Color>[
                    Colors.white.withAlpha(0),
                    Colors.white,
                    Colors.white,
                    Colors.white,
                    Colors.white.withAlpha(0)
                  ],
                ).createShader(bounds),
                blendMode: BlendMode.srcIn,
                child: OverflowBox(
                  maxHeight: 40,
                  child: AnimatedBuilder(
                    animation: _animdationController,
                    child: Column(
                      children: <Widget>[
                        Container(
                          height: 20,
                          child: Center(
                            child: Text(
                              labels[0],
                            ),
                          ),
                        ),
                        Container(
                          height: 20,
                          child: Center(
                            child: Text(
                              labels[1],
                            ),
                          ),
                        ),
                      ],
                    ),
                    builder: (BuildContext context, Widget child) {
                      return Transform.translate(
                        offset: Offset(
                          0,
                          Curves.slowMiddle
                                  .transform(_animdationController.value) *
                              20,
                        ),
                        child: child,
                      );
                    },
                  ),
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}