更改ExpansionPanelList.radio中ListTile后面的图标颜色
在ExpansionPanelList的ListTile中，试验已经以向下箭头的形式给出，当ListTile展开时，箭头变为向上箭头 然而，它是深色的。我添加了尾随：图标（诸如此类）。这只是在标题和默认的尾部按钮（向下箭头）之间添加了一个图标 如何更改默认尾随按钮的颜色，同时保持其多功能性，使其在框展开时变成向上箭头 我尝试将ListTile包装成一个主题，这是有人推荐的，但向下箭头的颜色没有改变，如下所示：更改ExpansionPanelList.radio中ListTile后面的图标颜色,list,flutter,colors,expansion,List,Flutter,Colors,Expansion,在ExpansionPanelList的ListTile中，试验已经以向下箭头的形式给出，当ListTile展开时，箭头变为向上箭头 然而，它是深色的。我添加了尾随：图标（诸如此类）。这只是在标题和默认的尾部按钮（向下箭头）之间添加了一个图标 如何更改默认尾随按钮的颜色，同时保持其多功能性，使其在框展开时变成向上箭头 我尝试将ListTile包装成一个主题，这是有人推荐的，但向下箭头的颜色没有改变，如下所示： Widget _buildPanel() { return Expansion
Widget _buildPanel() {
return ExpansionPanelList.radio(
initialOpenPanelValue: 0,
children: _data.map<ExpansionPanelRadio>((Item item) {
return ExpansionPanelRadio(
backgroundColor: Colors.black,
canTapOnHeader: true,
value: item.id,
headerBuilder: (BuildContext context, bool isExpanded) {
return Theme(
data: Theme.of(context)
.copyWith(unselectedWidgetColor: Colors.white),
child: ListTile(
title: Text(item.headerValue,
...
Widget\u buildPanel（）{
return ExpansionPanelList.radio(
initialOpenPanelValue:0，
子项：_data.map（（项）{
返回扩展面板收音机(
背景颜色：Colors.black，
坎塔波黑德：没错，
值：item.id，
headerBuilder：（BuildContext上下文，bool isExpanded）{
返回主题(
数据：主题（上下文）
.copyWith（未选择WidgetColor:Colors.white），
孩子：ListTile(
标题：文本（item.headerValue，
...
如果您使用的是
扩展面板列表扩展图标扩展图标 switch(Theme.of(context).brightness) {
case Brightness.light:
return Colors.black54;
case Brightness.dark:
return Colors.white60;
}
ExpansionPanelListexpansioniconexpansionpanelistcolor、disabledColor、expandedColor、expansionpanelistcoloredexpansionpanelistExpandI>con// The following code is the same that is found inside the Flutter framework
//just adding the `color,disabledColor,expandedColor` for personalizing the `ExpandedIcon`
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
const double _kPanelHeaderCollapsedHeight = kMinInteractiveDimension;
const EdgeInsets _kPanelHeaderExpandedDefaultPadding = EdgeInsets.symmetric(
vertical: 64.0 - _kPanelHeaderCollapsedHeight,
);
class _SaltedKey<S, V> extends LocalKey {
const _SaltedKey(this.salt, this.value);
final S salt;
final V value;
@override
bool operator ==(Object other) {
if (other.runtimeType != runtimeType)
return false;
return other is _SaltedKey<S, V>
&& other.salt == salt
&& other.value == value;
}
@override
int get hashCode => hashValues(runtimeType, salt, value);
@override
String toString() {
final String saltString = S == String ? "<'$salt'>" : '<$salt>';
final String valueString = V == String ? "<'$value'>" : '<$value>';
return '[$saltString $valueString]';
}
}
/// Signature for the callback that's called when an [ExpansionPanel] is
/// expanded or collapsed.
///
/// The position of the panel within an [ColoredExpansionPanelList] is given by
/// [panelIndex].
typedef ExpansionPanelCallback = void Function(int panelIndex, bool isExpanded);
/// Signature for the callback that's called when the header of the
/// [ExpansionPanel] needs to rebuild.
typedef ExpansionPanelHeaderBuilder = Widget Function(BuildContext context, bool isExpanded);
/// A material expansion panel. It has a header and a body and can be either
/// expanded or collapsed. The body of the panel is only visible when it is
/// expanded.
///
/// Expansion panels are only intended to be used as children for
/// [ColoredExpansionPanelList].
///
/// See [ColoredExpansionPanelList] for a sample implementation.
///
/// See also:
///
/// * [ColoredExpansionPanelList]
/// * <https://material.io/design/components/lists.html#types>
class ExpansionPanel {
/// Creates an expansion panel to be used as a child for [ColoredExpansionPanelList].
/// See [ColoredExpansionPanelList] for an example on how to use this widget.
///
/// The [headerBuilder], [body], and [isExpanded] arguments must not be null.
ExpansionPanel({
required this.headerBuilder,
required this.body,
this.isExpanded = false,
this.canTapOnHeader = false,
this.backgroundColor,
}) : assert(headerBuilder != null),
assert(body != null),
assert(isExpanded != null),
assert(canTapOnHeader != null);
/// The widget builder that builds the expansion panels' header.
final ExpansionPanelHeaderBuilder headerBuilder;
/// The body of the expansion panel that's displayed below the header.
///
/// This widget is visible only when the panel is expanded.
final Widget body;
/// Whether the panel is expanded.
///
/// Defaults to false.
final bool isExpanded;
/// Whether tapping on the panel's header will expand/collapse it.
///
/// Defaults to false.
final bool canTapOnHeader;
/// Defines the background color of the panel.
///
/// Defaults to [ThemeData.cardColor].
final Color? backgroundColor;
}
/// An expansion panel that allows for radio-like functionality.
/// This means that at any given time, at most, one [ExpansionPanelRadio]
/// can remain expanded.
///
/// A unique identifier [value] must be assigned to each panel.
/// This identifier allows the [ColoredExpansionPanelList] to determine
/// which [ExpansionPanelRadio] instance should be expanded.
///
/// See [ExpansionPanelList.radio] for a sample implementation.
class ExpansionPanelRadio extends ExpansionPanel {
/// An expansion panel that allows for radio functionality.
///
/// A unique [value] must be passed into the constructor. The
/// [headerBuilder], [body], [value] must not be null.
ExpansionPanelRadio({
required this.value,
required ExpansionPanelHeaderBuilder headerBuilder,
required Widget body,
bool canTapOnHeader = false,
Color? backgroundColor,
}) : assert(value != null),
super(
body: body,
headerBuilder: headerBuilder,
canTapOnHeader: canTapOnHeader,
backgroundColor: backgroundColor,
);
/// The value that uniquely identifies a radio panel so that the currently
/// selected radio panel can be identified.
final Object value;
}
/// A material expansion panel list that lays out its children and animates
/// expansions.
///
/// Note that [expansionCallback] behaves differently for [ColoredExpansionPanelList]
/// and [ExpansionPanelList.radio].
///
/// {@tool dartpad --template=stateful_widget_scaffold}
///
/// Here is a simple example of how to implement ExpansionPanelList.
///
/// ```dart preamble
/// // stores ExpansionPanel state information
/// class Item {
/// Item({
/// required this.expandedValue,
/// required this.headerValue,
/// this.isExpanded = false,
/// });
///
/// String expandedValue;
/// String headerValue;
/// bool isExpanded;
/// }
///
/// List<Item> generateItems(int numberOfItems) {
/// return List<Item>.generate(numberOfItems, (int index) {
/// return Item(
/// headerValue: 'Panel $index',
/// expandedValue: 'This is item number $index',
/// );
/// });
/// }
/// ```
///
/// ```dart
/// final List<Item> _data = generateItems(8);
///
/// @override
/// Widget build(BuildContext context) {
/// return SingleChildScrollView(
/// child: Container(
/// child: _buildPanel(),
/// ),
/// );
/// }
///
/// Widget _buildPanel() {
/// return ExpansionPanelList(
/// expansionCallback: (int index, bool isExpanded) {
/// setState(() {
/// _data[index].isExpanded = !isExpanded;
/// });
/// },
/// children: _data.map<ExpansionPanel>((Item item) {
/// return ExpansionPanel(
/// headerBuilder: (BuildContext context, bool isExpanded) {
/// return ListTile(
/// title: Text(item.headerValue),
/// );
/// },
/// body: ListTile(
/// title: Text(item.expandedValue),
/// subtitle: const Text('To delete this panel, tap the trash can icon'),
/// trailing: const Icon(Icons.delete),
/// onTap: () {
/// setState(() {
/// _data.removeWhere((Item currentItem) => item == currentItem);
/// });
/// }
/// ),
/// isExpanded: item.isExpanded,
/// );
/// }).toList(),
/// );
/// }
/// ```
/// {@end-tool}
///
/// See also:
///
/// * [ExpansionPanel]
/// * [ExpansionPanelList.radio]
/// * <https://material.io/design/components/lists.html#types>
class ColoredExpansionPanelList extends StatefulWidget {
/// Creates an expansion panel list widget. The [expansionCallback] is
/// triggered when an expansion panel expand/collapse button is pushed.
///
/// The [children] and [animationDuration] arguments must not be null.
const ColoredExpansionPanelList({
Key? key,
this.children = const <ExpansionPanel>[],
this.expansionCallback,
this.animationDuration = kThemeAnimationDuration,
this.expandedHeaderPadding = _kPanelHeaderExpandedDefaultPadding,
this.dividerColor,
this.color,
this.disabledColor,
this.expandedColor,
this.elevation = 2,
}) : assert(children != null),
assert(animationDuration != null),
_allowOnlyOnePanelOpen = false,
initialOpenPanelValue = null,
super(key: key);
/// START OF CUSTOM CODE TO ADD COLOR TO EXPANDEDICON
///
///
///
/// The color of the icon.
///
/// Defaults to [Colors.black54] when the theme's
/// [ThemeData.brightness] is [Brightness.light] and to
/// [Colors.white60] when it is [Brightness.dark]. This adheres to the
/// Material Design specifications for [icons](https://material.io/design/iconography/system-icons.html#color)
/// and for [dark theme](https://material.io/design/color/dark-theme.html#ui-application)
final Color? color;
/// The color of the icon when it is disabled,
/// i.e. if [onPressed] is null.
///
/// Defaults to [Colors.black38] when the theme's
/// [ThemeData.brightness] is [Brightness.light] and to
/// [Colors.white38] when it is [Brightness.dark]. This adheres to the
/// Material Design specifications for [icons](https://material.io/design/iconography/system-icons.html#color)
/// and for [dark theme](https://material.io/design/color/dark-theme.html#ui-application)
final Color? disabledColor;
/// The color of the icon when the icon is expanded.
///
/// Defaults to [Colors.black54] when the theme's
/// [ThemeData.brightness] is [Brightness.light] and to
/// [Colors.white] when it is [Brightness.dark]. This adheres to the
/// Material Design specifications for [icons](https://material.io/design/iconography/system-icons.html#color)
/// and for [dark theme](https://material.io/design/color/dark-theme.html#ui-application)
final Color? expandedColor;
///END OF CUSTOM CODE TO ADD COLOR TO EXPANDEDICON
///
///
///
///
///
/// Creates a radio expansion panel list widget.
///
/// This widget allows for at most one panel in the list to be open.
/// The expansion panel callback is triggered when an expansion panel
/// expand/collapse button is pushed. The [children] and [animationDuration]
/// arguments must not be null. The [children] objects must be instances
/// of [ExpansionPanelRadio].
///
/// {@tool dartpad --template=stateful_widget_scaffold}
///
/// Here is a simple example of how to implement ExpansionPanelList.radio.
///
/// ```dart preamble
/// // stores ExpansionPanel state information
/// class Item {
/// Item({
/// required this.id,
/// required this.expandedValue,
/// required this.headerValue,
/// });
///
/// int id;
/// String expandedValue;
/// String headerValue;
/// }
///
/// List<Item> generateItems(int numberOfItems) {
/// return List<Item>.generate(numberOfItems, (int index) {
/// return Item(
/// id: index,
/// headerValue: 'Panel $index',
/// expandedValue: 'This is item number $index',
/// );
/// });
/// }
/// ```
///
/// ```dart
/// final List<Item> _data = generateItems(8);
///
/// @override
/// Widget build(BuildContext context) {
/// return SingleChildScrollView(
/// child: Container(
/// child: _buildPanel(),
/// ),
/// );
/// }
///
/// Widget _buildPanel() {
/// return ExpansionPanelList.radio(
/// initialOpenPanelValue: 2,
/// children: _data.map<ExpansionPanelRadio>((Item item) {
/// return ExpansionPanelRadio(
/// value: item.id,
/// headerBuilder: (BuildContext context, bool isExpanded) {
/// return ListTile(
/// title: Text(item.headerValue),
/// );
/// },
/// body: ListTile(
/// title: Text(item.expandedValue),
/// subtitle: const Text('To delete this panel, tap the trash can icon'),
/// trailing: const Icon(Icons.delete),
/// onTap: () {
/// setState(() {
/// _data.removeWhere((Item currentItem) => item == currentItem);
/// });
/// }
/// )
/// );
/// }).toList(),
/// );
/// }
/// ```
/// {@end-tool}
const ColoredExpansionPanelList.radio({
Key? key,
this.children = const <ExpansionPanelRadio>[],
this.expansionCallback,
this.animationDuration = kThemeAnimationDuration,
this.initialOpenPanelValue,
this.expandedHeaderPadding = _kPanelHeaderExpandedDefaultPadding,
this.dividerColor,
this.color,
this.disabledColor,
this.expandedColor,
this.elevation = 2,
}) : assert(children != null),
assert(animationDuration != null),
_allowOnlyOnePanelOpen = true,
super(key: key);
/// The children of the expansion panel list. They are laid out in a similar
/// fashion to [ListBody].
final List<ExpansionPanel> children;
/// The callback that gets called whenever one of the expand/collapse buttons
/// is pressed. The arguments passed to the callback are the index of the
/// pressed panel and whether the panel is currently expanded or not.
///
/// If ExpansionPanelList.radio is used, the callback may be called a
/// second time if a different panel was previously open. The arguments
/// passed to the second callback are the index of the panel that will close
/// and false, marking that it will be closed.
///
/// For ExpansionPanelList, the callback needs to setState when it's notified
/// about the closing/opening panel. On the other hand, the callback for
/// ExpansionPanelList.radio is simply meant to inform the parent widget of
/// changes, as the radio panels' open/close states are managed internally.
///
/// This callback is useful in order to keep track of the expanded/collapsed
/// panels in a parent widget that may need to react to these changes.
final ExpansionPanelCallback? expansionCallback;
/// The duration of the expansion animation.
final Duration animationDuration;
// Whether multiple panels can be open simultaneously
final bool _allowOnlyOnePanelOpen;
/// The value of the panel that initially begins open. (This value is
/// only used when initializing with the [ExpansionPanelList.radio]
/// constructor.)
final Object? initialOpenPanelValue;
/// The padding that surrounds the panel header when expanded.
///
/// By default, 16px of space is added to the header vertically (above and below)
/// during expansion.
final EdgeInsets expandedHeaderPadding;
/// Defines color for the divider when [ExpansionPanel.isExpanded] is false.
///
/// If `dividerColor` is null, then [DividerThemeData.color] is used. If that
/// is null, then [ThemeData.dividerColor] is used.
final Color? dividerColor;
/// Defines elevation for the [ExpansionPanel] while it's expanded.
///
/// This uses [kElevationToShadow] to simulate shadows, it does not use
/// [Material]'s arbitrary elevation feature.
///
/// The following values can be used to define the elevation: 0, 1, 2, 3, 4, 6,
/// 8, 9, 12, 16, 24.
///
/// By default, the value of elevation is 2.
final int elevation;
@override
State<StatefulWidget> createState() => _ColoredExpansionPanelListState();
}
class _ColoredExpansionPanelListState extends State<ColoredExpansionPanelList> {
ExpansionPanelRadio? _currentOpenPanel;
@override
void initState() {
super.initState();
if (widget._allowOnlyOnePanelOpen) {
assert(_allIdentifiersUnique(), 'All ExpansionPanelRadio identifier values must be unique.');
if (widget.initialOpenPanelValue != null) {
_currentOpenPanel =
searchPanelByValue(widget.children.cast<ExpansionPanelRadio>(), widget.initialOpenPanelValue);
}
}
}
@override
void didUpdateWidget(ColoredExpansionPanelList oldWidget) {
super.didUpdateWidget(oldWidget);
if (widget._allowOnlyOnePanelOpen) {
assert(_allIdentifiersUnique(), 'All ExpansionPanelRadio identifier values must be unique.');
// If the previous widget was non-radio ExpansionPanelList, initialize the
// open panel to widget.initialOpenPanelValue
if (!oldWidget._allowOnlyOnePanelOpen) {
_currentOpenPanel =
searchPanelByValue(widget.children.cast<ExpansionPanelRadio>(), widget.initialOpenPanelValue);
}
} else {
_currentOpenPanel = null;
}
}
bool _allIdentifiersUnique() {
final Map<Object, bool> identifierMap = <Object, bool>{};
for (final ExpansionPanelRadio child in widget.children.cast<ExpansionPanelRadio>()) {
identifierMap[child.value] = true;
}
return identifierMap.length == widget.children.length;
}
bool _isChildExpanded(int index) {
if (widget._allowOnlyOnePanelOpen) {
final ExpansionPanelRadio radioWidget = widget.children[index] as ExpansionPanelRadio;
return _currentOpenPanel?.value == radioWidget.value;
}
return widget.children[index].isExpanded;
}
void _handlePressed(bool isExpanded, int index) {
widget.expansionCallback?.call(index, isExpanded);
if (widget._allowOnlyOnePanelOpen) {
final ExpansionPanelRadio pressedChild = widget.children[index] as ExpansionPanelRadio;
// If another ExpansionPanelRadio was already open, apply its
// expansionCallback (if any) to false, because it's closing.
for (int childIndex = 0; childIndex < widget.children.length; childIndex += 1) {
final ExpansionPanelRadio child = widget.children[childIndex] as ExpansionPanelRadio;
if (widget.expansionCallback != null &&
childIndex != index &&
child.value == _currentOpenPanel?.value)
widget.expansionCallback!(childIndex, false);
}
setState(() {
_currentOpenPanel = isExpanded ? null : pressedChild;
});
}
}
ExpansionPanelRadio? searchPanelByValue(List<ExpansionPanelRadio> panels, Object? value) {
for (final ExpansionPanelRadio panel in panels) {
if (panel.value == value)
return panel;
}
return null;
}
@override
Widget build(BuildContext context) {
assert(kElevationToShadow.containsKey(widget.elevation),
'Invalid value for elevation. See the kElevationToShadow constant for'
' possible elevation values.',
);
final List<MergeableMaterialItem> items = <MergeableMaterialItem>[];
for (int index = 0; index < widget.children.length; index += 1) {
if (_isChildExpanded(index) && index != 0 && !_isChildExpanded(index - 1))
items.add(MaterialGap(key: _SaltedKey<BuildContext, int>(context, index * 2 - 1)));
final ExpansionPanel child = widget.children[index];
final Widget headerWidget = child.headerBuilder(
context,
_isChildExpanded(index),
);
Widget expandIconContainer = Container(
margin: const EdgeInsetsDirectional.only(end: 8.0),
child: ExpandIcon(
color: widget.color,
disabledColor: widget.disabledColor,
expandedColor: widget.expandedColor,
isExpanded: _isChildExpanded(index),
padding: const EdgeInsets.all(16.0),
onPressed: !child.canTapOnHeader
? (bool isExpanded) => _handlePressed(isExpanded, index)
: null,
),
);
if (!child.canTapOnHeader) {
final MaterialLocalizations localizations = MaterialLocalizations.of(context);
expandIconContainer = Semantics(
label: _isChildExpanded(index)? localizations.expandedIconTapHint : localizations.collapsedIconTapHint,
container: true,
child: expandIconContainer,
);
}
Widget header = Row(
children: <Widget>[
Expanded(
child: AnimatedContainer(
duration: widget.animationDuration,
curve: Curves.fastOutSlowIn,
margin: _isChildExpanded(index) ? widget.expandedHeaderPadding : EdgeInsets.zero,
child: ConstrainedBox(
constraints: const BoxConstraints(minHeight: _kPanelHeaderCollapsedHeight),
child: headerWidget,
),
),
),
expandIconContainer,
],
);
if (child.canTapOnHeader) {
header = MergeSemantics(
child: InkWell(
onTap: () => _handlePressed(_isChildExpanded(index), index),
child: header,
),
);
}
items.add(
MaterialSlice(
key: _SaltedKey<BuildContext, int>(context, index * 2),
color: child.backgroundColor,
child: Column(
children: <Widget>[
header,
AnimatedCrossFade(
firstChild: Container(height: 0.0),
secondChild: child.body,
firstCurve: const Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
secondCurve: const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
sizeCurve: Curves.fastOutSlowIn,
crossFadeState: _isChildExpanded(index) ? CrossFadeState.showSecond : CrossFadeState.showFirst,
duration: widget.animationDuration,
),
],
),
),
);
if (_isChildExpanded(index) && index != widget.children.length - 1)
items.add(MaterialGap(key: _SaltedKey<BuildContext, int>(context, index * 2 + 1)));
}
return MergeableMaterial(
hasDividers: true,
dividerColor: widget.dividerColor,
elevation: widget.elevation,
children: items,
);
}
}
//以下代码与颤振框架中的代码相同
//只需添加'color，disabledColor，expandedColor'，即可对'ExpandedIcon'进行个性化设置`
//弗利特作者版权所有。保留所有权利。
//此源代码的使用受BSD样式许可证的约束，该许可证可以
//在许可证文件中找到。
进口“包装：颤振/材料.省道”；
导入“package:flatter/widgets.dart”；
常数double\u kPanelHeaderCollapsedHeight=KminiInteractiveDimension；
常量EdgeInsets\u kPanelHeaderExpandedDefaultPadding=EdgeInsets.symmetric(
垂直高度：64.0-kPanelHeaderCollapsed高度，
);
类_SaltedKey扩展了LocalKey{
常量SaltedKey（this.salt，this.value）；
最终的S盐；
最终V值；
@凌驾
布尔运算符==（对象其他）{
if（other.runtimeType！=runtimeType）
返回false；
返回另一个是SaltedKey
&&其他.盐==盐
&&other.value==值；
}
@凌驾
int get hashCode=>hashValues（runtimeType、salt、value）；
@凌驾
字符串toString（）{
最后一个字符串saltString=S==String？”：“”；
最终字符串值String=V==String？”：“”；
返回“[$saltString$valueString]”；
}
}
///调用[ExpansionPanel]时调用的回调的签名
///膨胀或崩溃。
///
///[ColoredExpansionPanelList]中面板的位置如下所示：
///[专题小组索引]。
typedef ExpansionPanelCallback=void函数（int-panelIndex，bool-isExpanded）；
///当
///[ExpansionPanel]需要重建。
typedef ExpansionPanelHeaderBuilder=小部件函数（BuildContext上下文，bool isExpanded）；
///材料扩展面板。它有一个标题和一个主体，可以是
///展开或折叠。面板主体仅在打开时可见
///扩大。
///
///扩展面板仅用于儿童
///[ColoredExpansionPanelList]。
///
///有关示例实现，请参见[ColoredExpansionPanelList]。
///
///另见：
///
///*[彩色扩展小组成员]
/// *
类扩展面板{
///创建要用作[ColoredExpansionPanelList]子级的扩展面板。
///有关如何使用此小部件的示例，请参见[ColoredExpansionPanelList]。
///
///[headerBuilder]、[body]和[isExpanded]参数不能为null。
扩展面板({
需要这个。headerBuilder，
需要这个机构，
this.isExpanded=false，
this.canTapOnHeader=false，
这个背景色，
})：assert（headerBuilder！=null），
断言（body！=null），
断言（isExpanded！=null），
断言（canTapOnHeader！=null）；
///构建扩展面板标题的小部件生成器。
最终扩展面板headerBuilder headerBuilder；
///标题下方显示的扩展面板主体。
///
///此小部件仅在面板展开时可见。
最终窗口小部件主体；
///面板是否展开。
///
///默认为false。
最终目标已扩展；
///轻敲面板标题是否会将其展开/折叠。
///
///默认为false。
最终布尔坎塔波黑德；
///定义面板的背景色。
///
///默认为[ThemeData.cardColor]。
最终颜色？背景色；
}
///一个扩展面板，允许类似无线电的功能。
///这意味着在任何给定的时间，最多有一个[ExpansionPanelRadio]
///可以继续扩大。
///
///必须为每个面板分配唯一标识符[值]。
///此标识符允许[ColoredExpansionPanelList]确定
///应该扩展哪个[ExpansionPanelRadio]实例。
///
///有关示例实现，请参见[ExpansionPanelList.radio]。
类ExpansionPanelRadio扩展了ExpansionPanel{
///允许无线电功能的扩展面板