flutter 绘制时间轴控件

先上图

难点 绘制时间轴与文字等高

正儿八经的方案计算每一个text的高度和 设置分割线的高度，方案3为取巧的可行方案
final text = 'Hello, world!';
final style = TextStyle(fontSize: 20);
final textSpan = TextSpan(text: text, style: style);
final textPainter = TextPainter(
  text: textSpan,
  textDirection: TextDirection.ltr,
);
textPainter.layout();
final height = textPainter.size.height;

1. 使用布局ListView>IntrinsicHeight>Row>ExpandableText
======== Exception caught by rendering library =====================================================
The following _CastError was thrown during performLayout():
Null check operator used on a null value

The relevant error-causing widget was: 
  ListView ListView:file:///D:/working/timelines/example/lib/main.dart:137:15
When the exception was thrown, this was the stack: 
#0      RenderSliverEdgeInsetsPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:149:63)
#1      RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:371:11)

2.ListView设置分割线  貌似只有水平的生效 垂直无效
ListView.separated(
  separatorBuilder: (BuildContext context, int index) => const VerticalDivider(),
  itemCount: 25,
  itemBuilder: (BuildContext context, int index) {
    return ListTile(title: Text('Item $index'));
  },
);

3.给item加边框绘制分割线
class ExamplePage extends StatelessWidget {
  List itemList = ['1', '2', '3'];

  @override
  Widget build(BuildContext context) {
    return TimelineTheme(
      data: TimelineThemeData(
        indicatorTheme: IndicatorThemeData(size: 15.0),
      ),
      child: Scaffold(
        appBar: AppBar(
          title: Text('Timelines Example'),
        ),
        body: ListView(
          padding: EdgeInsets.all(20.0),
          children: [
            Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Stack(
                  children: [
                    Container(
                      width: 6.5,
                      height: 6.5,
                      margin: EdgeInsets.only(top: 3.5),
                      decoration: BoxDecoration(
                          shape: BoxShape.circle,
                          border: Border.all(
                            color: Color(0xFF999999),
                            width: 1,
                          )),
                    ),
                    Padding(
                      padding: EdgeInsets.only(left: 10),
                      child: Text("20230703",
                          style: TextStyle(
                              color: Color(0xFF999999), fontSize: 12)),
                    )
                  ],
                ),
                Container(
                    padding: EdgeInsets.symmetric(horizontal: 6),
                    margin: EdgeInsets.only(left: 3),
                    decoration: BoxDecoration(
                        border: Border(
                      left: BorderSide(width: 1, color: Color(0xFFEEEEEE)),
                    )),
                    child: TimeLinesItem3()),
              ],
            ),
          ],
        ),
      ),
    );
  }

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

import 'expandable_text.dart';

//
class TimeLinesItem3 extends StatefulWidget {


  @override
  State<StatefulWidget> createState() {
    return LinesItemState();
  }
}

class LinesItemState extends State<TimeLinesItem3> {

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return
      Column(
        mainAxisSize: MainAxisSize.max,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Padding(
              padding: EdgeInsets.symmetric(vertical: 10),
              child: Text("AAAA Title",
                  maxLines: 2,
                  style: TextStyle(
                      color: Color(0xFF333333),
                      fontSize: 16,
                      height: 1.5,
                      fontWeight: FontWeight.bold))),
          ExpandableText(
            "AAAA Content在Flutter中，您可以使用Column组件来垂直排列子控件。默认情况下，子控件是居中对齐的。如果您想要左对齐，可以使用crossAxisAlignment属性。例如",
            expandText: 'aaaa',
            maxLines: 2,
            expandOnTextTap: true,
            collapseOnTextTap: true,
          ),
          Container(
            margin: EdgeInsets.only(top: 14, bottom: 6),
            padding: EdgeInsets.all(6),
            decoration: BoxDecoration(
              gradient: LinearGradient(
                colors: [Color(0x14FF3737), Color(0x05E93030)],
                begin: Alignment.topLeft,
                end: Alignment.bottomRight,
              ),
              borderRadius: BorderRadius.circular(4),
            ),
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                Text('普利特',
                    style: TextStyle(color: Color(0xFF333333), fontSize: 12)),
                Padding(padding: EdgeInsets.only(right: 10)),
                Text('4.08%',
                    style: TextStyle(color: Color(0xFFE93030), fontSize: 12)),
              ],
            ),
          ),
        ],
      );

  }

}