// Copyright 2017 The Chromium 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 'checkbox.dart'; import 'list_tile.dart'; import 'theme.dart'; import 'theme_data.dart'; // Examples can assume: // void setState(VoidCallback fn) { } /// A [ListTile] with a [Checkbox]. In other words, a checkbox with a label. /// /// The entire list tile is interactive: tapping anywhere in the tile toggles /// the checkbox. /// /// The [value], [onChanged], and [activeColor] properties of this widget are /// identical to the similarly-named properties on the [Checkbox] widget. /// /// 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 [value] state; to have the list tile /// appear selected when the checkbox is checked, pass the same value to both. /// /// The checkbox is shown on the right by default in left-to-right languages /// (i.e. the trailing 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 [CheckboxListTile] as disabled, pass null as the [onChanged] /// callback. /// /// {@tool snippet --template=stateful_widget_scaffold} /// /// ![CheckboxListTile sample](https://flutter.github.io/assets-for-api-docs/assets/material/checkbox_list_tile.png) /// /// This widget shows a checkbox that, when checked, slows down all animations /// (including the animation of the checkbox itself getting checked!). /// /// This sample requires that you also import 'package:flutter/scheduler.dart', /// so that you can reference [timeDilation]. /// /// ```dart imports /// import 'package:flutter/scheduler.dart' show timeDilation; /// ``` /// ```dart /// @override /// Widget build(BuildContext context) { /// return Center( /// child: CheckboxListTile( /// title: const Text('Animate Slowly'), /// value: timeDilation != 1.0, /// onChanged: (bool value) { /// setState(() { timeDilation = value ? 10.0 : 1.0; }); /// }, /// secondary: const Icon(Icons.hourglass_empty), /// ), /// ); /// } /// ``` /// {@end-tool} /// /// ## Semantics in CheckboxListTile /// /// Since the entirety of the CheckboxListTile is interactive, it should represent /// itself as a single interactive entity. /// /// To do so, a CheckboxListTile 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, CheckboxListTile 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 /// CheckboxListTile. [RichText] has an embedded gesture recognizer that /// requires its own [Semantics] node, which directly conflicts with /// CheckboxListTile'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 snippet --template=stateful_widget_scaffold} /// /// ![Checkbox list tile semantics sample](https://flutter.github.io/assets-for-api-docs/assets/material/checkbox_list_tile_semantics.png) /// /// Here is an example of a custom labeled checkbox widget, called /// LinkedLabelCheckbox, that includes an interactive [RichText] widget that /// handles tap gestures. /// /// ```dart imports /// import 'package:flutter/gestures.dart'; /// ``` /// ```dart preamble /// class LinkedLabelCheckbox extends StatelessWidget { /// const LinkedLabelCheckbox({ /// this.label, /// this.padding, /// this.value, /// this.onChanged, /// }); /// /// final String label; /// final EdgeInsets padding; /// final bool value; /// final Function onChanged; /// /// @override /// Widget build(BuildContext context) { /// return Padding( /// padding: padding, /// child: Row( /// children: <Widget>[ /// Expanded( /// child: RichText( /// text: TextSpan( /// text: label, /// style: TextStyle( /// color: Colors.blueAccent, /// decoration: TextDecoration.underline, /// ), /// recognizer: TapGestureRecognizer() /// ..onTap = () { /// print('Label has been tapped.'); /// }, /// ), /// ), /// ), /// Checkbox( /// value: value, /// onChanged: (bool newValue) { /// onChanged(newValue); /// }, /// ), /// ], /// ), /// ); /// } /// } /// ``` /// ```dart /// bool _isSelected = false; /// /// @override /// Widget build(BuildContext context) { /// return Scaffold( /// body: Center( /// child: LinkedLabelCheckbox( /// label: 'Linked, tappable label text', /// padding: const EdgeInsets.symmetric(horizontal: 20.0), /// value: _isSelected, /// onChanged: (bool newValue) { /// setState(() { /// _isSelected = newValue; /// }); /// }, /// ), /// ), /// ); /// } /// ``` /// {@end-tool} /// /// ## CheckboxListTile isn't exactly what I want /// /// If the way CheckboxListTile pads and positions its elements isn't quite /// what you're looking for, you can create custom labeled checkbox widgets by /// combining [Checkbox] with other widgets, such as [Text], [Padding] and /// [InkWell]. /// /// {@tool snippet --template=stateful_widget_scaffold} /// /// ![Custom checkbox list tile sample](https://flutter.github.io/assets-for-api-docs/assets/material/checkbox_list_tile_custom.png) /// /// Here is an example of a custom LabeledCheckbox widget, but you can easily /// make your own configurable widget. /// /// ```dart preamble /// class LabeledCheckbox extends StatelessWidget { /// const LabeledCheckbox({ /// this.label, /// this.padding, /// this.value, /// this.onChanged, /// }); /// /// final String label; /// final EdgeInsets padding; /// final bool value; /// final Function onChanged; /// /// @override /// Widget build(BuildContext context) { /// return InkWell( /// onTap: () { /// onChanged(!value); /// }, /// child: Padding( /// padding: padding, /// child: Row( /// children: <Widget>[ /// Expanded(child: Text(label)), /// Checkbox( /// value: value, /// onChanged: (bool newValue) { /// onChanged(newValue); /// }, /// ), /// ], /// ), /// ), /// ); /// } /// } /// ``` /// ```dart /// bool _isSelected = false; /// /// @override /// Widget build(BuildContext context) { /// return Scaffold( /// body: Center( /// child: LabeledCheckbox( /// label: 'This is the label text', /// padding: const EdgeInsets.symmetric(horizontal: 20.0), /// value: _isSelected, /// onChanged: (bool newValue) { /// setState(() { /// _isSelected = newValue; /// }); /// }, /// ), /// ), /// ); /// } /// ``` /// {@end-tool} /// /// See also: /// /// * [ListTileTheme], which can be used to affect the style of list tiles, /// including checkbox list tiles. /// * [RadioListTile], a similar widget for radio buttons. /// * [SwitchListTile], a similar widget for switches. /// * [ListTile] and [Checkbox], the widgets from which this widget is made. class CheckboxListTile extends StatelessWidget { /// Creates a combination of a list tile and a checkbox. /// /// The checkbox tile itself does not maintain any state. Instead, when the /// state of the checkbox changes, the widget calls the [onChanged] callback. /// Most widgets that use a checkbox will listen for the [onChanged] callback /// and rebuild the checkbox tile with a new [value] to update the visual /// appearance of the checkbox. /// /// The following arguments are required: /// /// * [value], which determines whether the checkbox is checked, and must not /// be null. /// /// * [onChanged], which is called when the value of the checkbox should /// change. It can be set to null to disable the checkbox. const CheckboxListTile({ Key key, @required this.value, @required this.onChanged, this.activeColor, this.title, this.subtitle, this.isThreeLine = false, this.dense, this.secondary, this.selected = false, this.controlAffinity = ListTileControlAffinity.platform, }) : assert(value != null), assert(isThreeLine != null), assert(!isThreeLine || subtitle != null), assert(selected != null), assert(controlAffinity != null), super(key: key); /// Whether this checkbox is checked. /// /// This property must not be null. final bool value; /// Called when the value of the checkbox should change. /// /// The checkbox passes the new value to the callback but does not actually /// change state until the parent widget rebuilds the checkbox tile with the /// new value. /// /// If null, the checkbox will be displayed as disabled. /// /// 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 /// CheckboxListTile( /// value: _throwShotAway, /// onChanged: (bool newValue) { /// setState(() { /// _throwShotAway = newValue; /// }); /// }, /// title: Text('Throw away your shot'), /// ) /// ``` final ValueChanged<bool> onChanged; /// The color to use when this checkbox is checked. /// /// 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 checkbox. /// /// 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 /// [value] state. To have the list tile appear selected when the checkbox is /// checked, pass the same value to both. /// /// 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; @override Widget build(BuildContext context) { final Widget control = Checkbox( value: value, onChanged: onChanged, activeColor: activeColor, materialTapTargetSize: MaterialTapTargetSize.shrinkWrap, ); Widget leading, trailing; switch (controlAffinity) { case ListTileControlAffinity.leading: leading = control; trailing = secondary; break; case ListTileControlAffinity.trailing: case ListTileControlAffinity.platform: 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 ? () { onChanged(!value); } : null, selected: selected, ), ), ); } }