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// 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';
/// 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.
/// ## Sample code
/// This widget shows a checkbox that, when checked, slows down all animations
/// (including the animation of the checkbox itself getting checked!).
/// ```dart
/// new CheckboxListTile(
/// title: const Text('Animate Slowly'),
/// value: timeDilation != 1.0,
/// onChanged: (bool value) {
/// setState(() { timeDilation = value ? 20.0 : 1.0; });
/// },
/// secondary: const Icon(Icons.hourglass_empty),
/// )
/// ```
/// This sample requires that you also import 'package:flutter/scheduler.dart',
/// so that you can reference [timeDilation].
/// 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.isThreeLine = false,
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
/// new CheckboxListTile(
/// value: _throwShotAway,
/// onChanged: (bool newValue) {
/// setState(() {
/// _throwShotAway = newValue;
/// });
/// },
/// title: new 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;
Widget build(BuildContext context) {
final Widget control = new Checkbox(
value: value,
onChanged: onChanged,
activeColor: activeColor,
materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
Widget leading, trailing;
switch (controlAffinity) {
case ListTileControlAffinity.leading:
leading = control;
trailing = secondary;
case ListTileControlAffinity.trailing:
case ListTileControlAffinity.platform:
leading = secondary;
trailing = control;
return new MergeSemantics(
child: ListTileTheme.merge(
selectedColor: activeColor ?? Theme.of(context).accentColor,
child: new ListTile(
leading: leading,
title: title,
subtitle: subtitle,
trailing: trailing,
isThreeLine: isThreeLine,
dense: dense,
enabled: onChanged != null,
onTap: onChanged != null ? () { onChanged(!value); } : null,
selected: selected,