如何在Flutter中自定义文本动画？

在Flutter中自定义文本动画可以通过使用动画控制器（AnimationController）和动画构建器（AnimatedBuilder）来实现。下面是一个简单的步骤指南：

导入Flutter动画库：

import 'package:flutter/material.dart';

创建一个有状态的小部件（StatefulWidget）：

class CustomTextAnimation extends StatefulWidget {
  @override
  _CustomTextAnimationState createState() => _CustomTextAnimationState();
}

在状态类中定义动画控制器和动画：

class _CustomTextAnimationState extends State<CustomTextAnimation> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: Duration(seconds: 2),
      vsync: this,
    );
    _animation = Tween<double>(begin: 0, end: 1).animate(_controller);
    _controller.forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _animation,
      builder: (BuildContext context, Widget child) {
        return Opacity(
          opacity: _animation.value,
          child: Text(
            'Custom Text Animation',
            style: TextStyle(fontSize: 24),
          ),
        );
      },
    );
  }
}