packages/flutter/lib/src/material/expansion_panel.dart - mirrors/flutter - Git at Google

 // Copyright 2016 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/rendering.dart';
 import 'package:flutter/widgets.dart';

 import 'expand_icon.dart';
 import 'mergeable_material.dart';
 import 'theme.dart';

 const double _kPanelHeaderCollapsedHeight = 48.0;
 const double _kPanelHeaderExpandedHeight = 64.0;

 class _SaltedKey<S, V> extends LocalKey {
   const _SaltedKey(this.salt, this.value);

   final S salt;
   final V value;

   @override
   bool operator ==(dynamic other) {
     if (other.runtimeType != runtimeType)
       return false;
     final _SaltedKey<S, V> typedOther = other;
     return salt == typedOther.salt
         && value == typedOther.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 [ExpansionPanelList] is given by
 /// [panelIndex].
 typedef void ExpansionPanelCallback(int panelIndex, bool isExpanded);

 /// Signature for the callback that's called when the header of the
 /// [ExpansionPanel] needs to rebuild.
 typedef Widget ExpansionPanelHeaderBuilder(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
 /// [ExpansionPanelList].
 ///
 /// See also:
 ///
 ///  * [ExpansionPanelList]
 ///  * <https://material.google.com/components/expansion-panels.html>
 class ExpansionPanel {
   /// Creates an expansion panel to be used as a child for [ExpansionPanelList].
   ///
   /// The [headerBuilder], [body], and [isExpanded] arguments must not be null.
   ExpansionPanel({
     @required this.headerBuilder,
     @required this.body,
     this.isExpanded = false
   }) : assert(headerBuilder != null),
        assert(body != null),
        assert(isExpanded != 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;

 }

 /// An expansion panel that allows for radio-like functionality.
 ///
 /// A unique identifier [value] must be assigned to each panel.
 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,
   }) : assert(value != null),
        super(body: body, headerBuilder: headerBuilder);

   /// 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.
 ///
 /// See also:
 ///
 ///  * [ExpansionPanel]
 ///  * <https://material.google.com/components/expansion-panels.html>
 class ExpansionPanelList 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 ExpansionPanelList({
     Key key,
     this.children = const <ExpansionPanel>[],
     this.expansionCallback,
     this.animationDuration = kThemeAnimationDuration,
   }) : assert(children != null),
        assert(animationDuration != null),
        _allowOnlyOnePanelOpen = false,
        this.initialOpenPanelValue = null,
        super(key: key);

   /// 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].
   const ExpansionPanelList.radio({
     Key key,
     List<ExpansionPanelRadio> children = const <ExpansionPanelRadio>[],
     this.expansionCallback,
     this.animationDuration = kThemeAnimationDuration,
     this.initialOpenPanelValue,
   }) : children = children, // ignore: prefer_initializing_formals
        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
   /// to-be-expanded panel in the list and whether the panel is currently
   /// expanded or not.
   ///
   /// 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;

   @override
   State<StatefulWidget> createState() => new _ExpansionPanelListState();
 }

 class _ExpansionPanelListState extends State<ExpansionPanelList> {
   ExpansionPanelRadio _currentOpenPanel;

   @override
   void initState() {
     super.initState();
     if (widget._allowOnlyOnePanelOpen) {
       assert(_allIdentifiersUnique(), 'All object identifiers are not unique!');
       for (ExpansionPanelRadio child in widget.children) {
         if (widget.initialOpenPanelValue != null &&
             child.value == widget.initialOpenPanelValue)
           _currentOpenPanel = child;
       }
     }
   }

   @override
   void didUpdateWidget(ExpansionPanelList oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (widget._allowOnlyOnePanelOpen) {
       assert(_allIdentifiersUnique(), 'All object identifiers are not unique!');
       for (ExpansionPanelRadio newChild in widget.children) {
         if (widget.initialOpenPanelValue != null &&
             newChild.value == widget.initialOpenPanelValue)
           _currentOpenPanel = newChild;
       }
     } else if(oldWidget._allowOnlyOnePanelOpen) {
       _currentOpenPanel = null;
     }
   }

   bool _allIdentifiersUnique() {
     final Map<Object, bool> identifierMap = <Object, bool>{};
     for (ExpansionPanelRadio child in widget.children) {
       identifierMap[child.value] = true;
     }
     return identifierMap.length == widget.children.length;
   }

   bool _isChildExpanded(int index) {
     if (widget._allowOnlyOnePanelOpen) {
       final ExpansionPanelRadio radioWidget = widget.children[index];
       return _currentOpenPanel?.value == radioWidget.value;
     }
     return widget.children[index].isExpanded;
   }

   void _handlePressed(bool isExpanded, int index) {
     if (widget.expansionCallback != null)
       widget.expansionCallback(index, isExpanded);

     if (widget._allowOnlyOnePanelOpen) {
       final ExpansionPanelRadio pressedChild = widget.children[index];

       for (int childIndex = 0; childIndex < widget.children.length; childIndex += 1) {
         final ExpansionPanelRadio child = widget.children[childIndex];
         if (widget.expansionCallback != null &&
             childIndex != index &&
             child.value == _currentOpenPanel?.value)
           widget.expansionCallback(childIndex, false);
       }
       _currentOpenPanel = isExpanded ? null : pressedChild;
     }
     setState((){});
   }

   @override
   Widget build(BuildContext context) {
     final List<MergeableMaterialItem> items = <MergeableMaterialItem>[];
     const EdgeInsets kExpandedEdgeInsets = EdgeInsets.symmetric(
       vertical: _kPanelHeaderExpandedHeight - _kPanelHeaderCollapsedHeight
     );

     for (int index = 0; index < widget.children.length; index += 1) {
       if (_isChildExpanded(index) && index != 0 && !_isChildExpanded(index - 1))
         items.add(new MaterialGap(key: new _SaltedKey<BuildContext, int>(context, index * 2 - 1)));

       final ExpansionPanel child = widget.children[index];
       final Row header = new Row(
         children: <Widget>[
           new Expanded(
             child: new AnimatedContainer(
               duration: widget.animationDuration,
               curve: Curves.fastOutSlowIn,
               margin: _isChildExpanded(index) ? kExpandedEdgeInsets : EdgeInsets.zero,
               child: new ConstrainedBox(
                 constraints: const BoxConstraints(minHeight: _kPanelHeaderCollapsedHeight),
                 child: child.headerBuilder(
                   context,
                   _isChildExpanded(index),
                 ),
               ),
             ),
           ),
           new Container(
             margin: const EdgeInsetsDirectional.only(end: 8.0),
             child: new ExpandIcon(
               isExpanded: _isChildExpanded(index),
               padding: const EdgeInsets.all(16.0),
               onPressed: (bool isExpanded) => _handlePressed(isExpanded, index),
             ),
           ),
         ],
       );

       items.add(
         new MaterialSlice(
           key: new _SaltedKey<BuildContext, int>(context, index * 2),
           child: new Column(
             children: <Widget>[
               new MergeSemantics(child: header),
               new AnimatedCrossFade(
                 firstChild: new 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(new MaterialGap(key: new _SaltedKey<BuildContext, int>(context, index * 2 + 1)));
     }

     return new MergeableMaterial(
       hasDividers: true,
       children: items,
     );
   }
 }
	// Copyright 2016 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/rendering.dart';
	import 'package:flutter/widgets.dart';

	import 'expand_icon.dart';
	import 'mergeable_material.dart';
	import 'theme.dart';

	const double _kPanelHeaderCollapsedHeight = 48.0;
	const double _kPanelHeaderExpandedHeight = 64.0;

	class _SaltedKey<S, V> extends LocalKey {
	const _SaltedKey(this.salt, this.value);

	final S salt;
	final V value;

	@override
	bool operator ==(dynamic other) {
	if (other.runtimeType != runtimeType)
	return false;
	final _SaltedKey<S, V> typedOther = other;
	return salt == typedOther.salt
	&& value == typedOther.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 [ExpansionPanelList] is given by
	/// [panelIndex].
	typedef void ExpansionPanelCallback(int panelIndex, bool isExpanded);

	/// Signature for the callback that's called when the header of the
	/// [ExpansionPanel] needs to rebuild.
	typedef Widget ExpansionPanelHeaderBuilder(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
	/// [ExpansionPanelList].
	///
	/// See also:
	///
	/// * [ExpansionPanelList]
	/// * <https://material.google.com/components/expansion-panels.html>
	class ExpansionPanel {
	/// Creates an expansion panel to be used as a child for [ExpansionPanelList].
	///
	/// The [headerBuilder], [body], and [isExpanded] arguments must not be null.
	ExpansionPanel({
	@required this.headerBuilder,
	@required this.body,
	this.isExpanded = false
	}) : assert(headerBuilder != null),
	assert(body != null),
	assert(isExpanded != 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;

	}

	/// An expansion panel that allows for radio-like functionality.
	///
	/// A unique identifier [value] must be assigned to each panel.
	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,
	}) : assert(value != null),
	super(body: body, headerBuilder: headerBuilder);

	/// 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.
	///
	/// See also:
	///
	/// * [ExpansionPanel]
	/// * <https://material.google.com/components/expansion-panels.html>
	class ExpansionPanelList 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 ExpansionPanelList({
	Key key,
	this.children = const <ExpansionPanel>[],
	this.expansionCallback,
	this.animationDuration = kThemeAnimationDuration,
	}) : assert(children != null),
	assert(animationDuration != null),
	_allowOnlyOnePanelOpen = false,
	this.initialOpenPanelValue = null,
	super(key: key);

	/// 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].
	const ExpansionPanelList.radio({
	Key key,
	List<ExpansionPanelRadio> children = const <ExpansionPanelRadio>[],
	this.expansionCallback,
	this.animationDuration = kThemeAnimationDuration,
	this.initialOpenPanelValue,
	}) : children = children, // ignore: prefer_initializing_formals
	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
	/// to-be-expanded panel in the list and whether the panel is currently
	/// expanded or not.
	///
	/// 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;

	@override
	State<StatefulWidget> createState() => new _ExpansionPanelListState();
	}

	class _ExpansionPanelListState extends State<ExpansionPanelList> {
	ExpansionPanelRadio _currentOpenPanel;

	@override
	void initState() {
	super.initState();
	if (widget._allowOnlyOnePanelOpen) {
	assert(_allIdentifiersUnique(), 'All object identifiers are not unique!');
	for (ExpansionPanelRadio child in widget.children) {
	if (widget.initialOpenPanelValue != null &&
	child.value == widget.initialOpenPanelValue)
	_currentOpenPanel = child;
	}
	}
	}

	@override
	void didUpdateWidget(ExpansionPanelList oldWidget) {
	super.didUpdateWidget(oldWidget);
	if (widget._allowOnlyOnePanelOpen) {
	assert(_allIdentifiersUnique(), 'All object identifiers are not unique!');
	for (ExpansionPanelRadio newChild in widget.children) {
	if (widget.initialOpenPanelValue != null &&
	newChild.value == widget.initialOpenPanelValue)
	_currentOpenPanel = newChild;
	}
	} else if(oldWidget._allowOnlyOnePanelOpen) {
	_currentOpenPanel = null;
	}
	}

	bool _allIdentifiersUnique() {
	final Map<Object, bool> identifierMap = <Object, bool>{};
	for (ExpansionPanelRadio child in widget.children) {
	identifierMap[child.value] = true;
	}
	return identifierMap.length == widget.children.length;
	}

	bool _isChildExpanded(int index) {
	if (widget._allowOnlyOnePanelOpen) {
	final ExpansionPanelRadio radioWidget = widget.children[index];
	return _currentOpenPanel?.value == radioWidget.value;
	}
	return widget.children[index].isExpanded;
	}

	void _handlePressed(bool isExpanded, int index) {
	if (widget.expansionCallback != null)
	widget.expansionCallback(index, isExpanded);

	if (widget._allowOnlyOnePanelOpen) {
	final ExpansionPanelRadio pressedChild = widget.children[index];

	for (int childIndex = 0; childIndex < widget.children.length; childIndex += 1) {
	final ExpansionPanelRadio child = widget.children[childIndex];
	if (widget.expansionCallback != null &&
	childIndex != index &&
	child.value == _currentOpenPanel?.value)
	widget.expansionCallback(childIndex, false);
	}
	_currentOpenPanel = isExpanded ? null : pressedChild;
	}
	setState((){});
	}

	@override
	Widget build(BuildContext context) {
	final List<MergeableMaterialItem> items = <MergeableMaterialItem>[];
	const EdgeInsets kExpandedEdgeInsets = EdgeInsets.symmetric(
	vertical: _kPanelHeaderExpandedHeight - _kPanelHeaderCollapsedHeight
	);

	for (int index = 0; index < widget.children.length; index += 1) {
	if (_isChildExpanded(index) && index != 0 && !_isChildExpanded(index - 1))
	items.add(new MaterialGap(key: new _SaltedKey<BuildContext, int>(context, index * 2 - 1)));

	final ExpansionPanel child = widget.children[index];
	final Row header = new Row(
	children: <Widget>[
	new Expanded(
	child: new AnimatedContainer(
	duration: widget.animationDuration,
	curve: Curves.fastOutSlowIn,
	margin: _isChildExpanded(index) ? kExpandedEdgeInsets : EdgeInsets.zero,
	child: new ConstrainedBox(
	constraints: const BoxConstraints(minHeight: _kPanelHeaderCollapsedHeight),
	child: child.headerBuilder(
	context,
	_isChildExpanded(index),
	),
	),
	),
	),
	new Container(
	margin: const EdgeInsetsDirectional.only(end: 8.0),
	child: new ExpandIcon(
	isExpanded: _isChildExpanded(index),
	padding: const EdgeInsets.all(16.0),
	onPressed: (bool isExpanded) => _handlePressed(isExpanded, index),
	),
	),
	],
	);

	items.add(
	new MaterialSlice(
	key: new _SaltedKey<BuildContext, int>(context, index * 2),
	child: new Column(
	children: <Widget>[
	new MergeSemantics(child: header),
	new AnimatedCrossFade(
	firstChild: new 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(new MaterialGap(key: new _SaltedKey<BuildContext, int>(context, index * 2 + 1)));
	}

	return new MergeableMaterial(
	hasDividers: true,
	children: items,
	);
	}
	}