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// 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/widgets.dart';
import 'list_tile.dart';
import 'radio.dart';
import 'theme.dart';
import 'theme_data.dart';
// Examples can assume:
// void setState(VoidCallback fn) { }
/// A [ListTile] with a [Radio]. In other words, a radio button with a label.
///
/// The entire list tile is interactive: tapping anywhere in the tile selects
/// the radio button.
///
/// The [value], [groupValue], [onChanged], and [activeColor] properties of this
/// widget are identical to the similarly-named properties on the [Radio]
/// widget. The type parameter `T` serves the same purpose as that of the
/// [Radio] class' type parameter.
///
/// The [title], [subtitle], [isThreeLine], and [dense] properties are like
/// those of the same name on [ListTile].
///
/// The [selected] property on this widget is similar to the [ListTile.selected]
/// property, but the color used is that described by [activeColor], if any,
/// defaulting to the accent color of the current [Theme]. No effort is made to
/// coordinate the [selected] state and the [checked] state; to have the list
/// tile appear selected when the radio button is the selected radio button, set
/// [selected] to true when [value] matches [groupValue].
///
/// The radio button is shown on the left by default in left-to-right languages
/// (i.e. the leading edge). This can be changed using [controlAffinity]. The
/// [secondary] widget is placed on the opposite side. This maps to the
/// [ListTile.leading] and [ListTile.trailing] properties of [ListTile].
///
/// To show the [RadioListTile] as disabled, pass null as the [onChanged]
/// callback.
///
/// {@tool dartpad --template=stateful_widget_scaffold}
///
/// ![RadioListTile sample](https://flutter.github.io/assets-for-api-docs/assets/material/radio_list_tile.png)
///
/// This widget shows a pair of radio buttons that control the `_character`
/// field. The field is of the type `SingingCharacter`, an enum.
///
/// ```dart preamble
/// enum SingingCharacter { lafayette, jefferson }
/// ```
/// ```dart
/// SingingCharacter _character = SingingCharacter.lafayette;
///
/// @override
/// Widget build(BuildContext context) {
/// return Column(
/// children: <Widget>[
/// RadioListTile<SingingCharacter>(
/// title: const Text('Lafayette'),
/// value: SingingCharacter.lafayette,
/// groupValue: _character,
/// onChanged: (SingingCharacter value) { setState(() { _character = value; }); },
/// ),
/// RadioListTile<SingingCharacter>(
/// title: const Text('Thomas Jefferson'),
/// value: SingingCharacter.jefferson,
/// groupValue: _character,
/// onChanged: (SingingCharacter value) { setState(() { _character = value; }); },
/// ),
/// ],
/// );
/// }
/// ```
/// {@end-tool}
///
/// ## Semantics in RadioListTile
///
/// Since the entirety of the RadioListTile is interactive, it should represent
/// itself as a single interactive entity.
///
/// To do so, a RadioListTile widget wraps its children with a [MergeSemantics]
/// widget. [MergeSemantics] will attempt to merge its descendant [Semantics]
/// nodes into one node in the semantics tree. Therefore, RadioListTile will
/// throw an error if any of its children requires its own [Semantics] node.
///
/// For example, you cannot nest a [RichText] widget as a descendant of
/// RadioListTile. [RichText] has an embedded gesture recognizer that
/// requires its own [Semantics] node, which directly conflicts with
/// RadioListTile's desire to merge all its descendants' semantic nodes
/// into one. Therefore, it may be necessary to create a custom radio tile
/// widget to accommodate similar use cases.
///
/// {@tool dartpad --template=stateful_widget_scaffold}
///
/// ![Radio list tile semantics sample](https://flutter.github.io/assets-for-api-docs/assets/material/radio_list_tile_semantics.png)
///
/// Here is an example of a custom labeled radio widget, called
/// LinkedLabelRadio, that includes an interactive [RichText] widget that
/// handles tap gestures.
///
/// ```dart imports
/// import 'package:flutter/gestures.dart';
/// ```
/// ```dart preamble
/// class LinkedLabelRadio extends StatelessWidget {
/// const LinkedLabelRadio({
/// this.label,
/// this.padding,
/// this.groupValue,
/// this.value,
/// this.onChanged,
/// });
///
/// final String label;
/// final EdgeInsets padding;
/// final bool groupValue;
/// final bool value;
/// final Function onChanged;
///
/// @override
/// Widget build(BuildContext context) {
/// return Padding(
/// padding: padding,
/// child: Row(
/// children: <Widget>[
/// Radio<bool>(
/// groupValue: groupValue,
/// value: value,
/// onChanged: (bool newValue) {
/// onChanged(newValue);
/// }
/// ),
/// RichText(
/// text: TextSpan(
/// text: label,
/// style: TextStyle(
/// color: Colors.blueAccent,
/// decoration: TextDecoration.underline,
/// ),
/// recognizer: TapGestureRecognizer()
/// ..onTap = () {
/// print('Label has been tapped.');
/// },
/// ),
/// ),
/// ],
/// ),
/// );
/// }
/// }
/// ```
/// ```dart
/// bool _isRadioSelected = false;
///
/// @override
/// Widget build(BuildContext context) {
/// return Scaffold(
/// body: Column(
/// mainAxisAlignment: MainAxisAlignment.center,
/// children: <Widget>[
/// LinkedLabelRadio(
/// label: 'First tappable label text',
/// padding: EdgeInsets.symmetric(horizontal: 5.0),
/// value: true,
/// groupValue: _isRadioSelected,
/// onChanged: (bool newValue) {
/// setState(() {
/// _isRadioSelected = newValue;
/// });
/// },
/// ),
/// LinkedLabelRadio(
/// label: 'Second tappable label text',
/// padding: EdgeInsets.symmetric(horizontal: 5.0),
/// value: false,
/// groupValue: _isRadioSelected,
/// onChanged: (bool newValue) {
/// setState(() {
/// _isRadioSelected = newValue;
/// });
/// },
/// ),
/// ],
/// ),
/// );
/// }
/// ```
/// {@end-tool}
///
/// ## RadioListTile isn't exactly what I want
///
/// If the way RadioListTile pads and positions its elements isn't quite what
/// you're looking for, you can create custom labeled radio widgets by
/// combining [Radio] with other widgets, such as [Text], [Padding] and
/// [InkWell].
///
/// {@tool dartpad --template=stateful_widget_scaffold}
///
/// ![Custom radio list tile sample](https://flutter.github.io/assets-for-api-docs/assets/material/radio_list_tile_custom.png)
///
/// Here is an example of a custom LabeledRadio widget, but you can easily
/// make your own configurable widget.
///
/// ```dart preamble
/// class LabeledRadio extends StatelessWidget {
/// const LabeledRadio({
/// this.label,
/// this.padding,
/// this.groupValue,
/// this.value,
/// this.onChanged,
/// });
///
/// final String label;
/// final EdgeInsets padding;
/// final bool groupValue;
/// final bool value;
/// final Function onChanged;
///
/// @override
/// Widget build(BuildContext context) {
/// return InkWell(
/// onTap: () {
/// if (value != groupValue)
/// onChanged(value);
/// },
/// child: Padding(
/// padding: padding,
/// child: Row(
/// children: <Widget>[
/// Radio<bool>(
/// groupValue: groupValue,
/// value: value,
/// onChanged: (bool newValue) {
/// onChanged(newValue);
/// },
/// ),
/// Text(label),
/// ],
/// ),
/// ),
/// );
/// }
/// }
/// ```
/// ```dart
/// bool _isRadioSelected = false;
///
/// @override
/// Widget build(BuildContext context) {
/// return Scaffold(
/// body: Column(
/// mainAxisAlignment: MainAxisAlignment.center,
/// children: <LabeledRadio>[
/// LabeledRadio(
/// label: 'This is the first label text',
/// padding: const EdgeInsets.symmetric(horizontal: 5.0),
/// value: true,
/// groupValue: _isRadioSelected,
/// onChanged: (bool newValue) {
/// setState(() {
/// _isRadioSelected = newValue;
/// });
/// },
/// ),
/// LabeledRadio(
/// label: 'This is the second label text',
/// padding: const EdgeInsets.symmetric(horizontal: 5.0),
/// value: false,
/// groupValue: _isRadioSelected,
/// onChanged: (bool newValue) {
/// setState(() {
/// _isRadioSelected = newValue;
/// });
/// },
/// ),
/// ],
/// ),
/// );
/// }
/// ```
/// {@end-tool}
///
/// See also:
///
/// * [ListTileTheme], which can be used to affect the style of list tiles,
/// including radio list tiles.
/// * [CheckboxListTile], a similar widget for checkboxes.
/// * [SwitchListTile], a similar widget for switches.
/// * [ListTile] and [Radio], the widgets from which this widget is made.
class RadioListTile<T> extends StatelessWidget {
/// Creates a combination of a list tile and a radio button.
///
/// The radio tile itself does not maintain any state. Instead, when the radio
/// button is selected, the widget calls the [onChanged] callback. Most
/// widgets that use a radio button will listen for the [onChanged] callback
/// and rebuild the radio tile with a new [groupValue] to update the visual
/// appearance of the radio button.
///
/// The following arguments are required:
///
/// * [value] and [groupValue] together determine whether the radio button is
/// selected.
/// * [onChanged] is called when the user selects this radio button.
const RadioListTile({
Key key,
@required this.value,
@required this.groupValue,
@required this.onChanged,
this.activeColor,
this.title,
this.subtitle,
this.isThreeLine = false,
this.dense,
this.secondary,
this.selected = false,
this.controlAffinity = ListTileControlAffinity.platform,
}) : assert(isThreeLine != null),
assert(!isThreeLine || subtitle != null),
assert(selected != null),
assert(controlAffinity != null),
super(key: key);
/// The value represented by this radio button.
final T value;
/// The currently selected value for this group of radio buttons.
///
/// This radio button is considered selected if its [value] matches the
/// [groupValue].
final T groupValue;
/// Called when the user selects this radio button.
///
/// The radio button passes [value] as a parameter to this callback. The radio
/// button does not actually change state until the parent widget rebuilds the
/// radio tile with the new [groupValue].
///
/// If null, the radio button will be displayed as disabled.
///
/// The provided callback will not be invoked if this radio button is already
/// selected.
///
/// The callback provided to [onChanged] should update the state of the parent
/// [StatefulWidget] using the [State.setState] method, so that the parent
/// gets rebuilt; for example:
///
/// ```dart
/// RadioListTile<SingingCharacter>(
/// title: const Text('Lafayette'),
/// value: SingingCharacter.lafayette,
/// groupValue: _character,
/// onChanged: (SingingCharacter newValue) {
/// setState(() {
/// _character = newValue;
/// });
/// },
/// )
/// ```
final ValueChanged<T> onChanged;
/// The color to use when this radio button is selected.
///
/// Defaults to accent color of the current [Theme].
final Color activeColor;
/// The primary content of the list tile.
///
/// Typically a [Text] widget.
final Widget title;
/// Additional content displayed below the title.
///
/// Typically a [Text] widget.
final Widget subtitle;
/// A widget to display on the opposite side of the tile from the radio button.
///
/// Typically an [Icon] widget.
final Widget secondary;
/// Whether this list tile is intended to display three lines of text.
///
/// If false, the list tile is treated as having one line if the subtitle is
/// null and treated as having two lines if the subtitle is non-null.
final bool isThreeLine;
/// Whether this list tile is part of a vertically dense list.
///
/// If this property is null then its value is based on [ListTileTheme.dense].
final bool dense;
/// Whether to render icons and text in the [activeColor].
///
/// No effort is made to automatically coordinate the [selected] state and the
/// [checked] state. To have the list tile appear selected when the radio
/// button is the selected radio button, set [selected] to true when [value]
/// matches [groupValue].
///
/// Normally, this property is left to its default value, false.
final bool selected;
/// Where to place the control relative to the text.
final ListTileControlAffinity controlAffinity;
/// Whether this radio button is checked.
///
/// To control this value, set [value] and [groupValue] appropriately.
bool get checked => value == groupValue;
@override
Widget build(BuildContext context) {
final Widget control = Radio<T>(
value: value,
groupValue: groupValue,
onChanged: onChanged,
activeColor: activeColor,
materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
);
Widget leading, trailing;
switch (controlAffinity) {
case ListTileControlAffinity.leading:
case ListTileControlAffinity.platform:
leading = control;
trailing = secondary;
break;
case ListTileControlAffinity.trailing:
leading = secondary;
trailing = control;
break;
}
return MergeSemantics(
child: ListTileTheme.merge(
selectedColor: activeColor ?? Theme.of(context).accentColor,
child: ListTile(
leading: leading,
title: title,
subtitle: subtitle,
trailing: trailing,
isThreeLine: isThreeLine,
dense: dense,
enabled: onChanged != null,
onTap: onChanged != null && !checked ? () { onChanged(value); } : null,
selected: selected,
),
),
);
}
}