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122 lines
2.9 KiB
Dart
122 lines
2.9 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/material.dart';
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class ExpansionTileSample extends StatelessWidget {
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@override
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Widget build(BuildContext context) {
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return MaterialApp(
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home: Scaffold(
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appBar: AppBar(
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title: const Text('ExpansionTile'),
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),
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body: ListView.builder(
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itemBuilder: (BuildContext context, int index) => EntryItem(data[index]),
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itemCount: data.length,
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),
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),
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);
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}
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}
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// One entry in the multilevel list displayed by this app.
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class Entry {
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Entry(this.title, [this.children = const <Entry>[]]);
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final String title;
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final List<Entry> children;
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}
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// The entire multilevel list displayed by this app.
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final List<Entry> data = <Entry>[
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Entry('Chapter A',
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<Entry>[
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Entry('Section A0',
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<Entry>[
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Entry('Item A0.1'),
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Entry('Item A0.2'),
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Entry('Item A0.3'),
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],
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),
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Entry('Section A1'),
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Entry('Section A2'),
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],
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),
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Entry('Chapter B',
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<Entry>[
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Entry('Section B0'),
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Entry('Section B1'),
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],
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),
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Entry('Chapter C',
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<Entry>[
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Entry('Section C0'),
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Entry('Section C1'),
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Entry('Section C2',
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<Entry>[
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Entry('Item C2.0'),
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Entry('Item C2.1'),
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Entry('Item C2.2'),
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Entry('Item C2.3'),
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],
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),
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],
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),
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];
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// Displays one Entry. If the entry has children then it's displayed
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// with an ExpansionTile.
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class EntryItem extends StatelessWidget {
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const EntryItem(this.entry);
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final Entry entry;
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Widget _buildTiles(Entry root) {
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if (root.children.isEmpty)
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return ListTile(title: Text(root.title));
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return ExpansionTile(
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key: PageStorageKey<Entry>(root),
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title: Text(root.title),
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children: root.children.map<Widget>(_buildTiles).toList(),
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);
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}
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@override
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Widget build(BuildContext context) {
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return _buildTiles(entry);
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}
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}
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void main() {
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runApp(ExpansionTileSample());
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}
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/*
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Sample Catalog
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Title: ExpansionTile
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Summary: An ExpansionTile for building nested lists, with two or more levels.
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Description:
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This app displays hierarchical data with ExpansionTiles. Tapping a tile
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expands or collapses the view of its children. When a tile is collapsed
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its children are disposed so that the widget footprint of the list only
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reflects what's visible.
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When displayed within a scrollable that creates its list items lazily,
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like a scrollable list created with `ListView.builder()`, ExpansionTiles
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can be quite efficient, particularly for material design "expand/collapse"
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lists.
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Classes: ExpansionTile, ListView
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Sample: ExpansionTileSample
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See also:
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- The "expand/collapse" part of the material design specification:
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<https://material.io/guidelines/components/lists-controls.html#lists-controls-types-of-list-controls>
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*/
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