Folding Flutter controls

1. Official controls ExpansionTiles fold

Official controls by default provides a folding listView ExpansionTiles mainly used to make folding and unfolding operations, take a look at general usage

Widget _buildTiles(Entry root) {
    return new ExpansionTile(
      title: new Text(root.title),
      children: root.children.map(_buildTiles).toList(),
    );
  }
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title is to click on the title of general, can be any Widget

children is folded and unfolded List

Very easy to use

2. Custom Controls folded ExpansionLayout

Due to the use of project control is controlled by an external folding Widget, involving some business logic, using the official controls ExpansionTiles, there is a lot of inconvenience, so the view ExpansionTiles, do their own modification according to ExpansionTiles source code, mainly based on the incoming external control field to expand and collapse

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

const Duration _kExpand = Duration(milliseconds: 200);

class ExpansionLayout extends StatefulWidget {
  const ExpansionLayout({
    Key key,
    this.backgroundColor,
    this.onExpansionChanged,
    this.children = const <Widget>[],
    this.trailing,
    this.isExpanded,
  }) : super(key: key);

  final ValueChanged<bool> onExpansionChanged;
  final List<Widget> children;

  final Color backgroundColor;
  //增加字段控制是否折叠
  final bool isExpanded;

  final Widget trailing;

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

class _ExpansionLayoutState extends State<ExpansionLayout>
    with SingleTickerProviderStateMixin {
//折叠展开的动画，主要是控制height
  static final Animatable<double> _easeInTween =
      CurveTween(curve: Curves.easeIn);
  AnimationController _controller;
  Animation<double> _heightFactor;

  bool _isExpanded;

  @override
  void initState() {
    super.initState();
    //初始化控制器以及出事状态
    _controller = AnimationController(duration: _kExpand, vsync: this);
    _heightFactor = _controller.drive(_easeInTween);
    _isExpanded = widget.isExpanded;
    if (_isExpanded) _controller.value = 1.0;
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void _handleTap() {
    setState(() {
      _isExpanded = widget.isExpanded;
      if (_isExpanded) {
        _controller.forward();
      } else {
        _controller.reverse().then<void>((void value) {
          if (!mounted) return;
        });
      }
      //保存页面数据
      PageStorage.of(context)?.writeState(context, _isExpanded);
    });
    //回调展开事件
    if (widget.onExpansionChanged != null)
      widget.onExpansionChanged(_isExpanded);
  }

  Widget _buildChildren(BuildContext context, Widget child) {
    return Container(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          ClipRect(
            child: Align(
              heightFactor: _heightFactor.value,
              child: child,
            ),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    //执行以下对应的Tap事件
    _handleTap();
    final bool closed = !_isExpanded && _controller.isDismissed;
    return AnimatedBuilder(
      animation: _controller.view,
      builder: _buildChildren,
      child: closed ? null : Column(children: widget.children),
    );
  }
}
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Principle is very simple, that is to control the folding and unfolding according to field _isExpanded, internal use animation to achieve control of the height of

Flutter current ecological resources is still very lacking, need a lot of customization, making changes based on general system-related controls, are the best

Reproduced in: https: //juejin.im/post/5d089d2bf265da1bb564fa84