packages/flutter/lib/src/material/search.dart - external/github.com/flutter/flutter - Git at Google

 // 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/foundation.dart';
 import 'package:flutter/widgets.dart';

 import 'app_bar.dart';
 import 'colors.dart';
 import 'debug.dart';
 import 'input_border.dart';
 import 'input_decorator.dart';
 import 'material_localizations.dart';
 import 'scaffold.dart';
 import 'text_field.dart';
 import 'theme.dart';

 /// Shows a full screen search page and returns the search result selected by
 /// the user when the page is closed.
 ///
 /// The search page consists of an app bar with a search field and a body which
 /// can either show suggested search queries or the search results.
 ///
 /// The appearance of the search page is determined by the provided
 /// `delegate`. The initial query string is given by `query`, which defaults
 /// to the empty string. When `query` is set to null, `delegate.query` will
 /// be used as the initial query.
 ///
 /// This method returns the selected search result, which can be set in the
 /// [SearchDelegate.close] call. If the search page is closed with the system
 /// back button, it returns null.
 ///
 /// A given [SearchDelegate] can only be associated with one active [showSearch]
 /// call. Call [SearchDelegate.close] before re-using the same delegate instance
 /// for another [showSearch] call.
 ///
 /// The transition to the search page triggered by this method looks best if the
 /// screen triggering the transition contains an [AppBar] at the top and the
 /// transition is called from an [IconButton] that's part of [AppBar.actions].
 /// The animation provided by [SearchDelegate.transitionAnimation] can be used
 /// to trigger additional animations in the underlying page while the search
 /// page fades in or out. This is commonly used to animate an [AnimatedIcon] in
 /// the [AppBar.leading] position e.g. from the hamburger menu to the back arrow
 /// used to exit the search page.
 ///
 /// ## Handling emojis and other complex characters
 /// {@macro flutter.widgets.editableText.complexCharacters}
 ///
 /// See also:
 ///
 ///  * [SearchDelegate] to define the content of the search page.
 Future<T> showSearch<T>({
   required BuildContext context,
   required SearchDelegate<T> delegate,
   String? query = '',
 }) {
   assert(delegate != null);
   assert(context != null);
   delegate.query = query ?? delegate.query;
   delegate._currentBody = _SearchBody.suggestions;
   return Navigator.of(context)!.push(_SearchPageRoute<T>(
     delegate: delegate,
   ));
 }

 /// Delegate for [showSearch] to define the content of the search page.
 ///
 /// The search page always shows an [AppBar] at the top where users can
 /// enter their search queries. The buttons shown before and after the search
 /// query text field can be customized via [SearchDelegate.buildLeading] and
 /// [SearchDelegate.buildActions].
 ///
 /// The body below the [AppBar] can either show suggested queries (returned by
 /// [SearchDelegate.buildSuggestions]) or - once the user submits a search  - the
 /// results of the search as returned by [SearchDelegate.buildResults].
 ///
 /// [SearchDelegate.query] always contains the current query entered by the user
 /// and should be used to build the suggestions and results.
 ///
 /// The results can be brought on screen by calling [SearchDelegate.showResults]
 /// and you can go back to showing the suggestions by calling
 /// [SearchDelegate.showSuggestions].
 ///
 /// Once the user has selected a search result, [SearchDelegate.close] should be
 /// called to remove the search page from the top of the navigation stack and
 /// to notify the caller of [showSearch] about the selected search result.
 ///
 /// A given [SearchDelegate] can only be associated with one active [showSearch]
 /// call. Call [SearchDelegate.close] before re-using the same delegate instance
 /// for another [showSearch] call.
 ///
 /// ## Handling emojis and other complex characters
 /// {@macro flutter.widgets.editableText.complexCharacters}
 abstract class SearchDelegate<T> {

   /// Constructor to be called by subclasses which may specify [searchFieldLabel], [keyboardType] and/or
   /// [textInputAction].
   ///
   /// {@tool snippet}
   /// ```dart
   /// class CustomSearchHintDelegate extends SearchDelegate {
   ///   CustomSearchHintDelegate({
   ///     String hintText,
   ///   }) : super(
   ///     searchFieldLabel: hintText,
   ///     keyboardType: TextInputType.text,
   ///     textInputAction: TextInputAction.search,
   ///   );
   ///
   ///   @override
   ///   Widget buildLeading(BuildContext context) => Text("leading");
   ///
   ///   @override
   ///   Widget buildSuggestions(BuildContext context) => Text("suggestions");
   ///
   ///   @override
   ///   Widget buildResults(BuildContext context) => Text('results');
   ///
   ///   @override
   ///   List<Widget> buildActions(BuildContext context) => [];
   /// }
   /// ```
   /// {@end-tool}
   SearchDelegate({
     this.searchFieldLabel,
     this.searchFieldStyle,
     this.keyboardType,
     this.textInputAction = TextInputAction.search,
   });

   /// Suggestions shown in the body of the search page while the user types a
   /// query into the search field.
   ///
   /// The delegate method is called whenever the content of [query] changes.
   /// The suggestions should be based on the current [query] string. If the query
   /// string is empty, it is good practice to show suggested queries based on
   /// past queries or the current context.
   ///
   /// Usually, this method will return a [ListView] with one [ListTile] per
   /// suggestion. When [ListTile.onTap] is called, [query] should be updated
   /// with the corresponding suggestion and the results page should be shown
   /// by calling [showResults].
   Widget buildSuggestions(BuildContext context);

   /// The results shown after the user submits a search from the search page.
   ///
   /// The current value of [query] can be used to determine what the user
   /// searched for.
   ///
   /// This method might be applied more than once to the same query.
   /// If your [buildResults] method is computationally expensive, you may want
   /// to cache the search results for one or more queries.
   ///
   /// Typically, this method returns a [ListView] with the search results.
   /// When the user taps on a particular search result, [close] should be called
   /// with the selected result as argument. This will close the search page and
   /// communicate the result back to the initial caller of [showSearch].
   Widget buildResults(BuildContext context);

   /// A widget to display before the current query in the [AppBar].
   ///
   /// Typically an [IconButton] configured with a [BackButtonIcon] that exits
   /// the search with [close]. One can also use an [AnimatedIcon] driven by
   /// [transitionAnimation], which animates from e.g. a hamburger menu to the
   /// back button as the search overlay fades in.
   ///
   /// Returns null if no widget should be shown.
   ///
   /// See also:
   ///
   ///  * [AppBar.leading], the intended use for the return value of this method.
   Widget buildLeading(BuildContext context);

   /// Widgets to display after the search query in the [AppBar].
   ///
   /// If the [query] is not empty, this should typically contain a button to
   /// clear the query and show the suggestions again (via [showSuggestions]) if
   /// the results are currently shown.
   ///
   /// Returns null if no widget should be shown.
   ///
   /// See also:
   ///
   ///  * [AppBar.actions], the intended use for the return value of this method.
   List<Widget> buildActions(BuildContext context);

   /// The theme used to style the [AppBar].
   ///
   /// By default, a white theme is used.
   ///
   /// See also:
   ///
   ///  * [AppBar.backgroundColor], which is set to [ThemeData.primaryColor].
   ///  * [AppBar.iconTheme], which is set to [ThemeData.primaryIconTheme].
   ///  * [AppBar.textTheme], which is set to [ThemeData.primaryTextTheme].
   ///  * [AppBar.brightness], which is set to [ThemeData.primaryColorBrightness].
   ThemeData appBarTheme(BuildContext context) {
     assert(context != null);
     final ThemeData theme = Theme.of(context)!;
     assert(theme != null);
     return theme.copyWith(
       primaryColor: Colors.white,
       primaryIconTheme: theme.primaryIconTheme.copyWith(color: Colors.grey),
       primaryColorBrightness: Brightness.light,
       primaryTextTheme: theme.textTheme,
     );
   }

   /// The current query string shown in the [AppBar].
   ///
   /// The user manipulates this string via the keyboard.
   ///
   /// If the user taps on a suggestion provided by [buildSuggestions] this
   /// string should be updated to that suggestion via the setter.
   String get query => _queryTextController.text;
   set query(String value) {
     assert(query != null);
     _queryTextController.text = value;
   }

   /// Transition from the suggestions returned by [buildSuggestions] to the
   /// [query] results returned by [buildResults].
   ///
   /// If the user taps on a suggestion provided by [buildSuggestions] the
   /// screen should typically transition to the page showing the search
   /// results for the suggested query. This transition can be triggered
   /// by calling this method.
   ///
   /// See also:
   ///
   ///  * [showSuggestions] to show the search suggestions again.
   void showResults(BuildContext context) {
     _focusNode?.unfocus();
     _currentBody = _SearchBody.results;
   }

   /// Transition from showing the results returned by [buildResults] to showing
   /// the suggestions returned by [buildSuggestions].
   ///
   /// Calling this method will also put the input focus back into the search
   /// field of the [AppBar].
   ///
   /// If the results are currently shown this method can be used to go back
   /// to showing the search suggestions.
   ///
   /// See also:
   ///
   ///  * [showResults] to show the search results.
   void showSuggestions(BuildContext context) {
     assert(_focusNode != null, '_focusNode must be set by route before showSuggestions is called.');
     _focusNode!.requestFocus();
     _currentBody = _SearchBody.suggestions;
   }

   /// Closes the search page and returns to the underlying route.
   ///
   /// The value provided for `result` is used as the return value of the call
   /// to [showSearch] that launched the search initially.
   void close(BuildContext context, T result) {
     _currentBody = null;
     _focusNode?.unfocus();
     Navigator.of(context)!
       ..popUntil((Route<dynamic> route) => route == _route)
       ..pop(result);
   }

   /// The hint text that is shown in the search field when it is empty.
   ///
   /// If this value is set to null, the value of
   /// `MaterialLocalizations.of(context).searchFieldLabel` will be used instead.
   final String? searchFieldLabel;

   /// The style of the [searchFieldLabel].
   ///
   /// If this value is set to null, the value of the ambient [Theme]'s
   /// [InputDecorationTheme.hintStyle] will be used instead.
   final TextStyle? searchFieldStyle;

   /// The type of action button to use for the keyboard.
   ///
   /// Defaults to the default value specified in [TextField].
   final TextInputType? keyboardType;

   /// The text input action configuring the soft keyboard to a particular action
   /// button.
   ///
   /// Defaults to [TextInputAction.search].
   final TextInputAction textInputAction;

   /// [Animation] triggered when the search pages fades in or out.
   ///
   /// This animation is commonly used to animate [AnimatedIcon]s of
   /// [IconButton]s returned by [buildLeading] or [buildActions]. It can also be
   /// used to animate [IconButton]s contained within the route below the search
   /// page.
   Animation<double> get transitionAnimation => _proxyAnimation;

   // The focus node to use for manipulating focus on the search page. This is
   // managed, owned, and set by the _SearchPageRoute using this delegate.
   FocusNode? _focusNode;

   final TextEditingController _queryTextController = TextEditingController();

   final ProxyAnimation _proxyAnimation = ProxyAnimation(kAlwaysDismissedAnimation);

   final ValueNotifier<_SearchBody?> _currentBodyNotifier = ValueNotifier<_SearchBody?>(null);

   _SearchBody? get _currentBody => _currentBodyNotifier.value;
   set _currentBody(_SearchBody? value) {
     _currentBodyNotifier.value = value;
   }

   _SearchPageRoute<T>? _route;
 }

 /// Describes the body that is currently shown under the [AppBar] in the
 /// search page.
 enum _SearchBody {
   /// Suggested queries are shown in the body.
   ///
   /// The suggested queries are generated by [SearchDelegate.buildSuggestions].
   suggestions,

   /// Search results are currently shown in the body.
   ///
   /// The search results are generated by [SearchDelegate.buildResults].
   results,
 }

 class _SearchPageRoute<T> extends PageRoute<T> {
   _SearchPageRoute({
     required this.delegate,
   }) : assert(delegate != null) {
     assert(
       delegate._route == null,
       'The ${delegate.runtimeType} instance is currently used by another active '
       'search. Please close that search by calling close() on the SearchDelegate '
       'before opening another search with the same delegate instance.',
     );
     delegate._route = this;
   }

   final SearchDelegate<T> delegate;

   @override
   Color? get barrierColor => null;

   @override
   String? get barrierLabel => null;

   @override
   Duration get transitionDuration => const Duration(milliseconds: 300);

   @override
   bool get maintainState => false;

   @override
   Widget buildTransitions(
     BuildContext context,
     Animation<double> animation,
     Animation<double> secondaryAnimation,
     Widget child,
   ) {
     return FadeTransition(
       opacity: animation,
       child: child,
     );
   }

   @override
   Animation<double> createAnimation() {
     final Animation<double> animation = super.createAnimation();
     delegate._proxyAnimation.parent = animation;
     return animation;
   }

   @override
   Widget buildPage(
     BuildContext context,
     Animation<double> animation,
     Animation<double> secondaryAnimation,
   ) {
     return _SearchPage<T>(
       delegate: delegate,
       animation: animation,
     );
   }

   @override
   void didComplete(T result) {
     super.didComplete(result);
     assert(delegate._route == this);
     delegate._route = null;
     delegate._currentBody = null;
   }
 }

 class _SearchPage<T> extends StatefulWidget {
   const _SearchPage({
     required this.delegate,
     required this.animation,
   });

   final SearchDelegate<T> delegate;
   final Animation<double> animation;

   @override
   State<StatefulWidget> createState() => _SearchPageState<T>();
 }

 class _SearchPageState<T> extends State<_SearchPage<T>> {
   // This node is owned, but not hosted by, the search page. Hosting is done by
   // the text field.
   FocusNode focusNode = FocusNode();

   @override
   void initState() {
     super.initState();
     widget.delegate._queryTextController.addListener(_onQueryChanged);
     widget.animation.addStatusListener(_onAnimationStatusChanged);
     widget.delegate._currentBodyNotifier.addListener(_onSearchBodyChanged);
     focusNode.addListener(_onFocusChanged);
     widget.delegate._focusNode = focusNode;
   }

   @override
   void dispose() {
     super.dispose();
     widget.delegate._queryTextController.removeListener(_onQueryChanged);
     widget.animation.removeStatusListener(_onAnimationStatusChanged);
     widget.delegate._currentBodyNotifier.removeListener(_onSearchBodyChanged);
     widget.delegate._focusNode = null;
     focusNode.dispose();
   }

   void _onAnimationStatusChanged(AnimationStatus status) {
     if (status != AnimationStatus.completed) {
       return;
     }
     widget.animation.removeStatusListener(_onAnimationStatusChanged);
     if (widget.delegate._currentBody == _SearchBody.suggestions) {
       focusNode.requestFocus();
     }
   }

   @override
   void didUpdateWidget(_SearchPage<T> oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (widget.delegate != oldWidget.delegate) {
       oldWidget.delegate._queryTextController.removeListener(_onQueryChanged);
       widget.delegate._queryTextController.addListener(_onQueryChanged);
       oldWidget.delegate._currentBodyNotifier.removeListener(_onSearchBodyChanged);
       widget.delegate._currentBodyNotifier.addListener(_onSearchBodyChanged);
       oldWidget.delegate._focusNode = null;
       widget.delegate._focusNode = focusNode;
     }
   }

   void _onFocusChanged() {
     if (focusNode.hasFocus && widget.delegate._currentBody != _SearchBody.suggestions) {
       widget.delegate.showSuggestions(context);
     }
   }

   void _onQueryChanged() {
     setState(() {
       // rebuild ourselves because query changed.
     });
   }

   void _onSearchBodyChanged() {
     setState(() {
       // rebuild ourselves because search body changed.
     });
   }

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterialLocalizations(context));
     final ThemeData theme = widget.delegate.appBarTheme(context);
     final String searchFieldLabel = widget.delegate.searchFieldLabel
       ?? MaterialLocalizations.of(context)!.searchFieldLabel;
     final TextStyle? searchFieldStyle = widget.delegate.searchFieldStyle
       ?? theme.inputDecorationTheme.hintStyle;
     Widget? body;
     switch(widget.delegate._currentBody) {
       case _SearchBody.suggestions:
         body = KeyedSubtree(
           key: const ValueKey<_SearchBody>(_SearchBody.suggestions),
           child: widget.delegate.buildSuggestions(context),
         );
         break;
       case _SearchBody.results:
         body = KeyedSubtree(
           key: const ValueKey<_SearchBody>(_SearchBody.results),
           child: widget.delegate.buildResults(context),
         );
         break;
       case null:
         break;
     }
     final String routeName;
     switch (theme.platform) {
       case TargetPlatform.iOS:
       case TargetPlatform.macOS:
         routeName = '';
         break;
       case TargetPlatform.android:
       case TargetPlatform.fuchsia:
       case TargetPlatform.linux:
       case TargetPlatform.windows:
         routeName = searchFieldLabel;
     }

     return Semantics(
       explicitChildNodes: true,
       scopesRoute: true,
       namesRoute: true,
       label: routeName,
       child: Scaffold(
         appBar: AppBar(
           backgroundColor: theme.primaryColor,
           iconTheme: theme.primaryIconTheme,
           textTheme: theme.primaryTextTheme,
           brightness: theme.primaryColorBrightness,
           leading: widget.delegate.buildLeading(context),
           title: TextField(
             controller: widget.delegate._queryTextController,
             focusNode: focusNode,
             style: theme.textTheme.headline6,
             textInputAction: widget.delegate.textInputAction,
             keyboardType: widget.delegate.keyboardType,
             onSubmitted: (String _) {
               widget.delegate.showResults(context);
             },
             decoration: InputDecoration(
               border: InputBorder.none,
               hintText: searchFieldLabel,
               hintStyle: searchFieldStyle,
             ),
           ),
           actions: widget.delegate.buildActions(context),
         ),
         body: AnimatedSwitcher(
           duration: const Duration(milliseconds: 300),
           child: body,
         ),
       ),
     );
   }
 }
	// 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/foundation.dart';
	import 'package:flutter/widgets.dart';

	import 'app_bar.dart';
	import 'colors.dart';
	import 'debug.dart';
	import 'input_border.dart';
	import 'input_decorator.dart';
	import 'material_localizations.dart';
	import 'scaffold.dart';
	import 'text_field.dart';
	import 'theme.dart';

	/// Shows a full screen search page and returns the search result selected by
	/// the user when the page is closed.
	///
	/// The search page consists of an app bar with a search field and a body which
	/// can either show suggested search queries or the search results.
	///
	/// The appearance of the search page is determined by the provided
	/// `delegate`. The initial query string is given by `query`, which defaults
	/// to the empty string. When `query` is set to null, `delegate.query` will
	/// be used as the initial query.
	///
	/// This method returns the selected search result, which can be set in the
	/// [SearchDelegate.close] call. If the search page is closed with the system
	/// back button, it returns null.
	///
	/// A given [SearchDelegate] can only be associated with one active [showSearch]
	/// call. Call [SearchDelegate.close] before re-using the same delegate instance
	/// for another [showSearch] call.
	///
	/// The transition to the search page triggered by this method looks best if the
	/// screen triggering the transition contains an [AppBar] at the top and the
	/// transition is called from an [IconButton] that's part of [AppBar.actions].
	/// The animation provided by [SearchDelegate.transitionAnimation] can be used
	/// to trigger additional animations in the underlying page while the search
	/// page fades in or out. This is commonly used to animate an [AnimatedIcon] in
	/// the [AppBar.leading] position e.g. from the hamburger menu to the back arrow
	/// used to exit the search page.
	///
	/// ## Handling emojis and other complex characters
	/// {@macro flutter.widgets.editableText.complexCharacters}
	///
	/// See also:
	///
	/// * [SearchDelegate] to define the content of the search page.
	Future<T> showSearch<T>({
	required BuildContext context,
	required SearchDelegate<T> delegate,
	String? query = '',
	}) {
	assert(delegate != null);
	assert(context != null);
	delegate.query = query ?? delegate.query;
	delegate._currentBody = _SearchBody.suggestions;
	return Navigator.of(context)!.push(_SearchPageRoute<T>(
	delegate: delegate,
	));
	}

	/// Delegate for [showSearch] to define the content of the search page.
	///
	/// The search page always shows an [AppBar] at the top where users can
	/// enter their search queries. The buttons shown before and after the search
	/// query text field can be customized via [SearchDelegate.buildLeading] and
	/// [SearchDelegate.buildActions].
	///
	/// The body below the [AppBar] can either show suggested queries (returned by
	/// [SearchDelegate.buildSuggestions]) or - once the user submits a search - the
	/// results of the search as returned by [SearchDelegate.buildResults].
	///
	/// [SearchDelegate.query] always contains the current query entered by the user
	/// and should be used to build the suggestions and results.
	///
	/// The results can be brought on screen by calling [SearchDelegate.showResults]
	/// and you can go back to showing the suggestions by calling
	/// [SearchDelegate.showSuggestions].
	///
	/// Once the user has selected a search result, [SearchDelegate.close] should be
	/// called to remove the search page from the top of the navigation stack and
	/// to notify the caller of [showSearch] about the selected search result.
	///
	/// A given [SearchDelegate] can only be associated with one active [showSearch]
	/// call. Call [SearchDelegate.close] before re-using the same delegate instance
	/// for another [showSearch] call.
	///
	/// ## Handling emojis and other complex characters
	/// {@macro flutter.widgets.editableText.complexCharacters}
	abstract class SearchDelegate<T> {

	/// Constructor to be called by subclasses which may specify [searchFieldLabel], [keyboardType] and/or
	/// [textInputAction].
	///
	/// {@tool snippet}
	/// ```dart
	/// class CustomSearchHintDelegate extends SearchDelegate {
	/// CustomSearchHintDelegate({
	/// String hintText,
	/// }) : super(
	/// searchFieldLabel: hintText,
	/// keyboardType: TextInputType.text,
	/// textInputAction: TextInputAction.search,
	/// );
	///
	/// @override
	/// Widget buildLeading(BuildContext context) => Text("leading");
	///
	/// @override
	/// Widget buildSuggestions(BuildContext context) => Text("suggestions");
	///
	/// @override
	/// Widget buildResults(BuildContext context) => Text('results');
	///
	/// @override
	/// List<Widget> buildActions(BuildContext context) => [];
	/// }
	/// ```
	/// {@end-tool}
	SearchDelegate({
	this.searchFieldLabel,
	this.searchFieldStyle,
	this.keyboardType,
	this.textInputAction = TextInputAction.search,
	});

	/// Suggestions shown in the body of the search page while the user types a
	/// query into the search field.
	///
	/// The delegate method is called whenever the content of [query] changes.
	/// The suggestions should be based on the current [query] string. If the query
	/// string is empty, it is good practice to show suggested queries based on
	/// past queries or the current context.
	///
	/// Usually, this method will return a [ListView] with one [ListTile] per
	/// suggestion. When [ListTile.onTap] is called, [query] should be updated
	/// with the corresponding suggestion and the results page should be shown
	/// by calling [showResults].
	Widget buildSuggestions(BuildContext context);

	/// The results shown after the user submits a search from the search page.
	///
	/// The current value of [query] can be used to determine what the user
	/// searched for.
	///
	/// This method might be applied more than once to the same query.
	/// If your [buildResults] method is computationally expensive, you may want
	/// to cache the search results for one or more queries.
	///
	/// Typically, this method returns a [ListView] with the search results.
	/// When the user taps on a particular search result, [close] should be called
	/// with the selected result as argument. This will close the search page and
	/// communicate the result back to the initial caller of [showSearch].
	Widget buildResults(BuildContext context);

	/// A widget to display before the current query in the [AppBar].
	///
	/// Typically an [IconButton] configured with a [BackButtonIcon] that exits
	/// the search with [close]. One can also use an [AnimatedIcon] driven by
	/// [transitionAnimation], which animates from e.g. a hamburger menu to the
	/// back button as the search overlay fades in.
	///
	/// Returns null if no widget should be shown.
	///
	/// See also:
	///
	/// * [AppBar.leading], the intended use for the return value of this method.
	Widget buildLeading(BuildContext context);

	/// Widgets to display after the search query in the [AppBar].
	///
	/// If the [query] is not empty, this should typically contain a button to
	/// clear the query and show the suggestions again (via [showSuggestions]) if
	/// the results are currently shown.
	///
	/// Returns null if no widget should be shown.
	///
	/// See also:
	///
	/// * [AppBar.actions], the intended use for the return value of this method.
	List<Widget> buildActions(BuildContext context);

	/// The theme used to style the [AppBar].
	///
	/// By default, a white theme is used.
	///
	/// See also:
	///
	/// * [AppBar.backgroundColor], which is set to [ThemeData.primaryColor].
	/// * [AppBar.iconTheme], which is set to [ThemeData.primaryIconTheme].
	/// * [AppBar.textTheme], which is set to [ThemeData.primaryTextTheme].
	/// * [AppBar.brightness], which is set to [ThemeData.primaryColorBrightness].
	ThemeData appBarTheme(BuildContext context) {
	assert(context != null);
	final ThemeData theme = Theme.of(context)!;
	assert(theme != null);
	return theme.copyWith(
	primaryColor: Colors.white,
	primaryIconTheme: theme.primaryIconTheme.copyWith(color: Colors.grey),
	primaryColorBrightness: Brightness.light,
	primaryTextTheme: theme.textTheme,
	);
	}

	/// The current query string shown in the [AppBar].
	///
	/// The user manipulates this string via the keyboard.
	///
	/// If the user taps on a suggestion provided by [buildSuggestions] this
	/// string should be updated to that suggestion via the setter.
	String get query => _queryTextController.text;
	set query(String value) {
	assert(query != null);
	_queryTextController.text = value;
	}

	/// Transition from the suggestions returned by [buildSuggestions] to the
	/// [query] results returned by [buildResults].
	///
	/// If the user taps on a suggestion provided by [buildSuggestions] the
	/// screen should typically transition to the page showing the search
	/// results for the suggested query. This transition can be triggered
	/// by calling this method.
	///
	/// See also:
	///
	/// * [showSuggestions] to show the search suggestions again.
	void showResults(BuildContext context) {
	_focusNode?.unfocus();
	_currentBody = _SearchBody.results;
	}

	/// Transition from showing the results returned by [buildResults] to showing
	/// the suggestions returned by [buildSuggestions].
	///
	/// Calling this method will also put the input focus back into the search
	/// field of the [AppBar].
	///
	/// If the results are currently shown this method can be used to go back
	/// to showing the search suggestions.
	///
	/// See also:
	///
	/// * [showResults] to show the search results.
	void showSuggestions(BuildContext context) {
	assert(_focusNode != null, '_focusNode must be set by route before showSuggestions is called.');
	_focusNode!.requestFocus();
	_currentBody = _SearchBody.suggestions;
	}

	/// Closes the search page and returns to the underlying route.
	///
	/// The value provided for `result` is used as the return value of the call
	/// to [showSearch] that launched the search initially.
	void close(BuildContext context, T result) {
	_currentBody = null;
	_focusNode?.unfocus();
	Navigator.of(context)!
	..popUntil((Route<dynamic> route) => route == _route)
	..pop(result);
	}

	/// The hint text that is shown in the search field when it is empty.
	///
	/// If this value is set to null, the value of
	/// `MaterialLocalizations.of(context).searchFieldLabel` will be used instead.
	final String? searchFieldLabel;

	/// The style of the [searchFieldLabel].
	///
	/// If this value is set to null, the value of the ambient [Theme]'s
	/// [InputDecorationTheme.hintStyle] will be used instead.
	final TextStyle? searchFieldStyle;

	/// The type of action button to use for the keyboard.
	///
	/// Defaults to the default value specified in [TextField].
	final TextInputType? keyboardType;

	/// The text input action configuring the soft keyboard to a particular action
	/// button.
	///
	/// Defaults to [TextInputAction.search].
	final TextInputAction textInputAction;

	/// [Animation] triggered when the search pages fades in or out.
	///
	/// This animation is commonly used to animate [AnimatedIcon]s of
	/// [IconButton]s returned by [buildLeading] or [buildActions]. It can also be
	/// used to animate [IconButton]s contained within the route below the search
	/// page.
	Animation<double> get transitionAnimation => _proxyAnimation;

	// The focus node to use for manipulating focus on the search page. This is
	// managed, owned, and set by the _SearchPageRoute using this delegate.
	FocusNode? _focusNode;

	final TextEditingController _queryTextController = TextEditingController();

	final ProxyAnimation _proxyAnimation = ProxyAnimation(kAlwaysDismissedAnimation);

	final ValueNotifier<_SearchBody?> _currentBodyNotifier = ValueNotifier<_SearchBody?>(null);

	_SearchBody? get _currentBody => _currentBodyNotifier.value;
	set _currentBody(_SearchBody? value) {
	_currentBodyNotifier.value = value;
	}

	_SearchPageRoute<T>? _route;
	}

	/// Describes the body that is currently shown under the [AppBar] in the
	/// search page.
	enum _SearchBody {
	/// Suggested queries are shown in the body.
	///
	/// The suggested queries are generated by [SearchDelegate.buildSuggestions].
	suggestions,

	/// Search results are currently shown in the body.
	///
	/// The search results are generated by [SearchDelegate.buildResults].
	results,
	}

	class _SearchPageRoute<T> extends PageRoute<T> {
	_SearchPageRoute({
	required this.delegate,
	}) : assert(delegate != null) {
	assert(
	delegate._route == null,
	'The ${delegate.runtimeType} instance is currently used by another active '
	'search. Please close that search by calling close() on the SearchDelegate '
	'before opening another search with the same delegate instance.',
	);
	delegate._route = this;
	}

	final SearchDelegate<T> delegate;

	@override
	Color? get barrierColor => null;

	@override
	String? get barrierLabel => null;

	@override
	Duration get transitionDuration => const Duration(milliseconds: 300);

	@override
	bool get maintainState => false;

	@override
	Widget buildTransitions(
	BuildContext context,
	Animation<double> animation,
	Animation<double> secondaryAnimation,
	Widget child,
	) {
	return FadeTransition(
	opacity: animation,
	child: child,
	);
	}

	@override
	Animation<double> createAnimation() {
	final Animation<double> animation = super.createAnimation();
	delegate._proxyAnimation.parent = animation;
	return animation;
	}

	@override
	Widget buildPage(
	BuildContext context,
	Animation<double> animation,
	Animation<double> secondaryAnimation,
	) {
	return _SearchPage<T>(
	delegate: delegate,
	animation: animation,
	);
	}

	@override
	void didComplete(T result) {
	super.didComplete(result);
	assert(delegate._route == this);
	delegate._route = null;
	delegate._currentBody = null;
	}
	}

	class _SearchPage<T> extends StatefulWidget {
	const _SearchPage({
	required this.delegate,
	required this.animation,
	});

	final SearchDelegate<T> delegate;
	final Animation<double> animation;

	@override
	State<StatefulWidget> createState() => _SearchPageState<T>();
	}

	class _SearchPageState<T> extends State<_SearchPage<T>> {
	// This node is owned, but not hosted by, the search page. Hosting is done by
	// the text field.
	FocusNode focusNode = FocusNode();

	@override
	void initState() {
	super.initState();
	widget.delegate._queryTextController.addListener(_onQueryChanged);
	widget.animation.addStatusListener(_onAnimationStatusChanged);
	widget.delegate._currentBodyNotifier.addListener(_onSearchBodyChanged);
	focusNode.addListener(_onFocusChanged);
	widget.delegate._focusNode = focusNode;
	}

	@override
	void dispose() {
	super.dispose();
	widget.delegate._queryTextController.removeListener(_onQueryChanged);
	widget.animation.removeStatusListener(_onAnimationStatusChanged);
	widget.delegate._currentBodyNotifier.removeListener(_onSearchBodyChanged);
	widget.delegate._focusNode = null;
	focusNode.dispose();
	}

	void _onAnimationStatusChanged(AnimationStatus status) {
	if (status != AnimationStatus.completed) {
	return;
	}
	widget.animation.removeStatusListener(_onAnimationStatusChanged);
	if (widget.delegate._currentBody == _SearchBody.suggestions) {
	focusNode.requestFocus();
	}
	}

	@override
	void didUpdateWidget(_SearchPage<T> oldWidget) {
	super.didUpdateWidget(oldWidget);
	if (widget.delegate != oldWidget.delegate) {
	oldWidget.delegate._queryTextController.removeListener(_onQueryChanged);
	widget.delegate._queryTextController.addListener(_onQueryChanged);
	oldWidget.delegate._currentBodyNotifier.removeListener(_onSearchBodyChanged);
	widget.delegate._currentBodyNotifier.addListener(_onSearchBodyChanged);
	oldWidget.delegate._focusNode = null;
	widget.delegate._focusNode = focusNode;
	}
	}

	void _onFocusChanged() {
	if (focusNode.hasFocus && widget.delegate._currentBody != _SearchBody.suggestions) {
	widget.delegate.showSuggestions(context);
	}
	}

	void _onQueryChanged() {
	setState(() {
	// rebuild ourselves because query changed.
	});
	}

	void _onSearchBodyChanged() {
	setState(() {
	// rebuild ourselves because search body changed.
	});
	}

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMaterialLocalizations(context));
	final ThemeData theme = widget.delegate.appBarTheme(context);
	final String searchFieldLabel = widget.delegate.searchFieldLabel
	?? MaterialLocalizations.of(context)!.searchFieldLabel;
	final TextStyle? searchFieldStyle = widget.delegate.searchFieldStyle
	?? theme.inputDecorationTheme.hintStyle;
	Widget? body;
	switch(widget.delegate._currentBody) {
	case _SearchBody.suggestions:
	body = KeyedSubtree(
	key: const ValueKey<_SearchBody>(_SearchBody.suggestions),
	child: widget.delegate.buildSuggestions(context),
	);
	break;
	case _SearchBody.results:
	body = KeyedSubtree(
	key: const ValueKey<_SearchBody>(_SearchBody.results),
	child: widget.delegate.buildResults(context),
	);
	break;
	case null:
	break;
	}
	final String routeName;
	switch (theme.platform) {
	case TargetPlatform.iOS:
	case TargetPlatform.macOS:
	routeName = '';
	break;
	case TargetPlatform.android:
	case TargetPlatform.fuchsia:
	case TargetPlatform.linux:
	case TargetPlatform.windows:
	routeName = searchFieldLabel;
	}

	return Semantics(
	explicitChildNodes: true,
	scopesRoute: true,
	namesRoute: true,
	label: routeName,
	child: Scaffold(
	appBar: AppBar(
	backgroundColor: theme.primaryColor,
	iconTheme: theme.primaryIconTheme,
	textTheme: theme.primaryTextTheme,
	brightness: theme.primaryColorBrightness,
	leading: widget.delegate.buildLeading(context),
	title: TextField(
	controller: widget.delegate._queryTextController,
	focusNode: focusNode,
	style: theme.textTheme.headline6,
	textInputAction: widget.delegate.textInputAction,
	keyboardType: widget.delegate.keyboardType,
	onSubmitted: (String _) {
	widget.delegate.showResults(context);
	},
	decoration: InputDecoration(
	border: InputBorder.none,
	hintText: searchFieldLabel,
	hintStyle: searchFieldStyle,
	),
	),
	actions: widget.delegate.buildActions(context),
	),
	body: AnimatedSwitcher(
	duration: const Duration(milliseconds: 300),
	child: body,
	),
	),
	);
	}
	}