Flutter: Trying to get a Widget that scrolls in 2D.

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(new TestApp());
}

class TestApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new TestAppHomePage(),
    );
  }
}

class TestAppHomePage extends StatefulWidget {
  TestAppHomePageState createState() => new TestAppHomePageState();
}

class TestAppHomePageState extends State<TestAppHomePage> {
  ScrollController _verticalScrollController;
  ScrollController _horizontalScrollController;

  @override
  void initState() {
    _verticalScrollController = new ScrollController();
    _horizontalScrollController = new ScrollController();
  }

  @override
  void dispose() {
    _verticalScrollController.dispose();
    _horizontalScrollController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: _buildNormalScrollView(),
//      body: _buildGridScrollView(),
//      body: _buildNestedScrollView(),
    );
  }

  Widget _buildGridScrollView() {
    return new GridView.builder(
      primary: false,
      controller: _horizontalScrollController,
      scrollDirection: Axis.horizontal,
      itemCount: 1,
      itemBuilder: (BuildContext context, int index) {
        _createContent();
      },
      gridDelegate:
          new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4),
    );
  }

  Widget _buildNormalScrollView() {
    return new GridView.count(
      primary: false,
      controller: _horizontalScrollController,
      scrollDirection: Axis.horizontal,
      crossAxisCount: 1,
      crossAxisSpacing: 20.0,
      children: <Widget>[
        SizedBox(
          width: 6800.0,
          child: _createContent(),
        )
      ],
    );
  }

  Widget _buildNestedScrollView() {
    return NestedScrollView(
      controller: _horizontalScrollController,
      scrollDirection: Axis.horizontal,
      headerSliverBuilder: (context, boxIsScrolled) {
        return <Widget>[
          SliverAppBar(
            title: Text("Example"),
            pinned: true,
            floating: true,
            forceElevated: boxIsScrolled,
          )
        ];
      },
      body: SizedBox(
        width: 2800.0,
        child: Row(
          children: <Widget>[
            SizedBox(
              width: 6800.0,
              child: _createContent(),
            )
          ],
        ),
      ),
    );
  }

  Widget _createContent() {
    return new SingleChildScrollView(
      primary: false,
      controller: _verticalScrollController,
      scrollDirection: Axis.vertical,
      child: new SizedBox(
        height: 2300.0,
        width: 2800.0,
        child: new Row(
          children: _createContentX(20),
        ),
      ),
    );
  }

  List<Widget> _createContentX(int count) {
    List<Widget> widgets = [];
    for (int i = 0; i < count; i++) {
      widgets.add(new Column(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: _createText(),
      ));
    }
    return widgets;
  }

  List<Widget> _createText() {
    return <Widget>[
      new Text("Line1"),
      new Text("Line2"),
      new Text("Line3"),
      new Text("Line4"),
      new Text("Line5"),
      new Text("Line6"),
      new Text("Line7"),
      new Text("Line8"),
      new Text("Line9"),
      new Text("Line10"),
      new Text("Line11"),
      new Text("Line12"),
      new Text("Line13"),
      new Text("Line14"),
      new Text("Line15"),
    ];
  }
}