scroll_to_index_with_offset 1.0.11

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  • Changelog
  • Example
  • Installing
  • 74

scroll-to-index-with-offset #

This package provides the scroll to index mechanism for fixed/variable row height for Flutter scrollable widget.

Getting Started #

In the pubspec.yaml of your flutter project, add the following dependency:

dependencies:
  ...
  scroll_to_index_with_offset: any

In your library add the following import:

import 'package:scroll_to_index_with_offset/scroll_to_index.dart';

For help getting started with Flutter, view the online documentation.

Usage #

This is a widget level library, means you can use this mechanism inside any Flutter scrollable widget.

Example for Flutter ListView

ListView(
  scrollDirection: scrollDirection,
  controller: controller,
  children: randomList.map<Widget>((data) {
  	final index = data[0];
  	final height = data[1];
    return AutoScrollTag(
      key: ValueKey(index),
      controller: controller,
      index: index,
      child: Text('index: $index, height: $height'),
      highlightColor: Colors.black.withOpacity(0.1),
    );
  }).toList(),
)

you can wrap any of your row widget which has dynamic row height

AutoScrollTag(
  key: ValueKey(index),
  controller: controller,
  index: index,
  child: child
)

with the AutoScrollController controller.

when you need to trigger scroll to a specified index, you can call

controller.scrollToIndex(index, preferPosition: AutoScrollPosition.begin, offset: 0) //Offset is optional 

even more, with a fixed row height, you can give it a suggested height for more efficient scrolling. there are more configuration.

final controller = AutoScrollController(
  //add this for advanced viewport boundary. e.g. SafeArea
  viewportBoundaryGetter: () => Rect.fromLTRB(0, 0, 0, MediaQuery.of(context).padding.bottom),

  //choose vertical/horizontal
  axis: scrollDirection,

  //this given value will bring the scroll offset to the nearest position in fixed row height case.
  //for variable row height case, you can still set the average height, it will try to get to the relatively closer offset 
  //and then start searching.
  suggestedRowHeight: 200
);

CHANGES #

1.0.0

  • public release

1.0.1

  • adjustment for extension

1.0.2

  • #7: cast to RenderBox of ctx.findRenderObject()

1.0.3

  • #15: InputConnection closed when calling highlight()

1.0.4

  • #16: setState cancels highlight

1.0.4+1

  • fix leaks

1.0.5

  • #17: scroll to a index when empty ScrollTag state shouldn't cause exception

1.0.6

  • support animated highlight

1.0.7

  • support scrolling with offset 1.0.8
  • Fix small bug 1.0.9
  • Fix small bug 1.0.10
  • Fix small bug 1.0.11
  • Fix small bug

example/lib/main.dart

//Copyright (C) 2019 Potix Corporation. All Rights Reserved.
//History: Tue Apr 24 09:29 CST 2019
// Author: Jerry Chen

import 'dart:math' as math;

import 'package:flutter/material.dart';
import 'package:scroll_to_index_with_offset/scroll_to_index.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: 'Scroll To Index Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Scroll To Index Demo'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  static const maxCount = 100;
  final random = math.Random();
  final scrollDirection = Axis.vertical;

  AutoScrollController controller;
  List<List<int>> randomList;

  @override
  void initState() {
    super.initState();
    controller = AutoScrollController(
      viewportBoundaryGetter: () => Rect.fromLTRB(0, 0, 0, MediaQuery.of(context).padding.bottom),
      axis: scrollDirection
    );
    randomList = List.generate(maxCount, (index) => <int>[index, (1000 * random.nextDouble()).toInt()]);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: ListView(
        scrollDirection: scrollDirection,
        controller: controller,
        children: randomList.map<Widget>((data) {
          return Padding(
            padding: EdgeInsets.all(8),
            child: _getRow(data[0], math.max(data[1].toDouble(), 50.0)),
          );
        }).toList(),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _scrollToIndex,
        tooltip: 'Increment',
        child: Text(counter.toString()),
      ),
    );
  }

  int counter = -1;
  Future _scrollToIndex() async {
    setState(() {
      counter++;

      if (counter >= maxCount)
        counter = 0;
    });

    await controller.scrollToIndex(counter, preferPosition: AutoScrollPosition.begin, offset: -50);
    controller.highlight(counter);
  }

  Widget _getRow(int index, double height) {
    return _wrapScrollTag(
      index: index,
      child: Container(
        padding: EdgeInsets.all(8),
        alignment: Alignment.topCenter,
        height: height,
        decoration: BoxDecoration(
          border: Border.all(
            color: Colors.lightBlue,
            width: 4
          ),
          borderRadius: BorderRadius.circular(12)
        ),
        child: Text('index: $index, height: $height'),
      )
    );
  }

  Widget _wrapScrollTag({int index, Widget child})
  => AutoScrollTag(
    key: ValueKey(index),
    controller: controller,
    index: index,
    child: child,
    highlightColor: Colors.black.withOpacity(0.1),
  );
}

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:


dependencies:
  scroll_to_index_with_offset: ^1.0.11

2. Install it

You can install packages from the command line:

with Flutter:


$ flutter pub get

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:scroll_to_index_with_offset/scroll_to_index.dart';
import 'package:scroll_to_index_with_offset/util.dart';
  
Popularity:
Describes how popular the package is relative to other packages. [more]
51
Health:
Code health derived from static analysis. [more]
100
Maintenance:
Reflects how tidy and up-to-date the package is. [more]
95
Overall:
Weighted score of the above. [more]
74
Learn more about scoring.

We analyzed this package on Jul 10, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.8.4
  • pana: 0.13.15
  • Flutter: 1.17.5

Analysis suggestions

Package not compatible with SDK dart

Because:

  • scroll_to_index_with_offset that is a package requiring null.

Health suggestions

Format lib/scroll_to_index.dart.

Run flutter format to format lib/scroll_to_index.dart.

Format lib/util.dart.

Run flutter format to format lib/util.dart.

Maintenance suggestions

The package description is too short. (-5 points)

Add more detail to the description field of pubspec.yaml. Use 60 to 180 characters to describe the package, what it does, and its target use case.

Dependencies

Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.1.0 <3.0.0
flutter 0.0.0
Transitive dependencies
collection 1.14.12 1.14.13
meta 1.1.8 1.2.2
sky_engine 0.0.99
typed_data 1.1.6 1.2.0
vector_math 2.0.8 2.1.0-nullsafety
Dev dependencies
flutter_test