Flutter-自定义可展开文本控件

import 'package:flutter/material.dart';
 
class ExpandableText extends StatefulWidget {
  final String text;
  final int maxLines;
  final String expandText;
  final String collapseText;
 
  const ExpandableText(this.text, this.maxLines, this.expandText, this.collapseText, {Key? key}) : super(key: key);
 
  @override
  _ExpandableTextState createState() => _ExpandableTextState();
}
 
class _ExpandableTextState extends State<ExpandableText> {
  bool _isExpanded = false;
 
  void _toggleExpanded() {
    setState(() {
      _isExpanded = !_isExpanded;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        ConstrainedBox(
          constraints: BoxConstraints(maxHeight: _isExpanded ? double.infinity : (widget.maxLines * 1.2)), // 1.2 is an empirical coefficient to provide some buffer
          child: AnimatedSize(
            duration: const Duration(milliseconds: 200),
            vsync: this,
            child: _isExpanded ? null : Text(widget.text),
          ),
        ),
        TextButton(
          onPressed: _toggleExpanded,
          child: Text(_isExpanded ? widget.collapseText : widget.expandText),
        ),
      ],
    );
  }
}

这段代码定义了一个名为ExpandableText的有状态组件，它允许用户展开或折叠文本。组件有四个参数：text、maxLines、expandText和collapseText。maxLines限制了文本在折叠状态下显示的最大行数，而expandText和collapseText是显示在按钮上的文本。组件的状态包括_isExpanded，它记录了文本是否处于展开状态。_toggleExpanded方法用于切换_isExpanded的值，从而允许用户展开或折叠文本。