anchor_scroll_controller 0.4.4

This package implement a ScrollController which supports anchor. That is, AnchorScrollController supports to scroll to index and listen to index changed while scrolling by user.

example/lib/main.dart

import 'package:example/cascaded_scroll_controller.dart';
import 'package:example/offset_scroll_view.dart';
import 'package:example/pin_scroll_view.dart';
import 'package:example/general_scroll_view.dart';
import 'package:flutter/material.dart';
import 'package:modal_bottom_sheet/modal_bottom_sheet.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'AnchorScrollController example'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>{

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Center(
            child: TextButton(
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all<Color>(Colors.green),
                foregroundColor: MaterialStateProperty.all<Color>(Colors.black),
                fixedSize: MaterialStateProperty.all<Size>(Size(200, 50)),
              ),
              onPressed: () {
                Navigator.push(context, MaterialPageRoute(builder: (context) {
                  return GeneralScrollViewWidget();
                }));
              },
              child: Text("GeneralScrollView"),
            ),
          ),
          SizedBox(height: 20,),
          Center(
            child: TextButton(
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all<Color>(Colors.green),
                foregroundColor: MaterialStateProperty.all<Color>(Colors.black),
                fixedSize: MaterialStateProperty.all<Size>(Size(200, 50)),
              ),
              onPressed: () {
                Navigator.push(context, MaterialPageRoute(builder: (context) {
                  return PinScrollViewWidget();
                }));
              },
              child: Text("PinScrollView"),
            ),
          ),
          SizedBox(height: 20,),
          Center(
            child: TextButton(
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all<Color>(Colors.green),
                foregroundColor: MaterialStateProperty.all<Color>(Colors.black),
                fixedSize: MaterialStateProperty.all<Size>(Size(200, 50)),
              ),
              onPressed: () {
                showMaterialModalBottomSheet(context: context, builder: (context) => CascadesScrollControllerWidget(ModalScrollController.of(context)!));
              },
              child: Text("CascadedScrollView"),
            ),
          ),
          SizedBox(height: 20,),
          Center(
            child: TextButton(
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all<Color>(Colors.green),
                foregroundColor: MaterialStateProperty.all<Color>(Colors.black),
                fixedSize: MaterialStateProperty.all<Size>(Size(200, 50)),
              ),
              onPressed: () {
                Navigator.push(context, MaterialPageRoute(builder: (context) {
                  return OffsetScrollViewWidget();
                }));
              },
              child: Text("Scroll with offset"),
            ),
          ),
        ],
      )
    );
  }
}