packages/flutter/lib/src/cupertino/bottom_tab_bar.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 'dart:ui' show ImageFilter;

 import 'package:flutter/widgets.dart';

 import 'colors.dart';
 import 'localizations.dart';
 import 'theme.dart';

 // Standard iOS 10 tab bar height.
 const double _kTabBarHeight = 50.0;

 const Color _kDefaultTabBarBorderColor = CupertinoDynamicColor.withBrightness(
   color: Color(0x4C000000),
   darkColor: Color(0x29000000),
 );
 const Color _kDefaultTabBarInactiveColor = CupertinoColors.inactiveGray;

 /// An iOS-styled bottom navigation tab bar.
 ///
 /// Displays multiple tabs using [BottomNavigationBarItem] with one tab being
 /// active, the first tab by default.
 ///
 /// This [StatelessWidget] doesn't store the active tab itself. You must
 /// listen to the [onTap] callbacks and call `setState` with a new [currentIndex]
 /// for the new selection to reflect. This can also be done automatically
 /// by wrapping this with a [CupertinoTabScaffold].
 ///
 /// Tab changes typically trigger a switch between [Navigator]s, each with its
 /// own navigation stack, per standard iOS design. This can be done by using
 /// [CupertinoTabView]s inside each tab builder in [CupertinoTabScaffold].
 ///
 /// If the given [backgroundColor]'s opacity is not 1.0 (which is the case by
 /// default), it will produce a blurring effect to the content behind it.
 ///
 /// When used as [CupertinoTabScaffold.tabBar], by default `CupertinoTabBar` has
 /// its text scale factor set to 1.0 and does not respond to text scale factor
 /// changes from the operating system, to match the native iOS behavior. To override
 /// this behavior, wrap each of the `navigationBar`'s components inside a [MediaQuery]
 /// with the desired [MediaQueryData.textScaleFactor] value. The text scale factor
 /// value from the operating system can be retrieved in many ways, such as querying
 /// [MediaQuery.textScaleFactorOf] against [CupertinoApp]'s [BuildContext].
 ///
 /// {@tool dartpad}
 /// This example shows a [CupertinoTabBar] placed in a [CupertinoTabScaffold].
 ///
 /// ** See code in examples/api/lib/cupertino/bottom_tab_bar/bottom_tab_bar.0.dart **
 /// {@end-tool}
 ///
 /// See also:
 ///
 ///  * [CupertinoTabScaffold], which hosts the [CupertinoTabBar] at the bottom.
 ///  * [BottomNavigationBarItem], an item in a [CupertinoTabBar].
 class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
   /// Creates a tab bar in the iOS style.
   const CupertinoTabBar({
     Key? key,
     required this.items,
     this.onTap,
     this.currentIndex = 0,
     this.backgroundColor,
     this.activeColor,
     this.inactiveColor = _kDefaultTabBarInactiveColor,
     this.iconSize = 30.0,
     this.border = const Border(
       top: BorderSide(
         color: _kDefaultTabBarBorderColor,
         width: 0.0, // 0.0 means one physical pixel
       ),
     ),
   }) : assert(items != null),
        assert(
          items.length >= 2,
          "Tabs need at least 2 items to conform to Apple's HIG",
        ),
        assert(currentIndex != null),
        assert(0 <= currentIndex && currentIndex < items.length),
        assert(iconSize != null),
        assert(inactiveColor != null),
        super(key: key);

   /// The interactive items laid out within the bottom navigation bar.
   ///
   /// Must not be null.
   final List<BottomNavigationBarItem> items;

   /// The callback that is called when a item is tapped.
   ///
   /// The widget creating the bottom navigation bar needs to keep track of the
   /// current index and call `setState` to rebuild it with the newly provided
   /// index.
   final ValueChanged<int>? onTap;

   /// The index into [items] of the current active item.
   ///
   /// Must not be null and must inclusively be between 0 and the number of tabs
   /// minus 1.
   final int currentIndex;

   /// The background color of the tab bar. If it contains transparency, the
   /// tab bar will automatically produce a blurring effect to the content
   /// behind it.
   ///
   /// Defaults to [CupertinoTheme]'s `barBackgroundColor` when null.
   final Color? backgroundColor;

   /// The foreground color of the icon and title for the [BottomNavigationBarItem]
   /// of the selected tab.
   ///
   /// Defaults to [CupertinoTheme]'s `primaryColor` if null.
   final Color? activeColor;

   /// The foreground color of the icon and title for the [BottomNavigationBarItem]s
   /// in the unselected state.
   ///
   /// Defaults to a [CupertinoDynamicColor] that matches the disabled foreground
   /// color of the native `UITabBar` component. Cannot be null.
   final Color inactiveColor;

   /// The size of all of the [BottomNavigationBarItem] icons.
   ///
   /// This value is used to configure the [IconTheme] for the navigation bar.
   /// When a [BottomNavigationBarItem.icon] widget is not an [Icon] the widget
   /// should configure itself to match the icon theme's size and color.
   ///
   /// Must not be null.
   final double iconSize;

   /// The border of the [CupertinoTabBar].
   ///
   /// The default value is a one physical pixel top border with grey color.
   final Border? border;

   @override
   Size get preferredSize => const Size.fromHeight(_kTabBarHeight);

   /// Indicates whether the tab bar is fully opaque or can have contents behind
   /// it show through it.
   bool opaque(BuildContext context) {
     final Color backgroundColor =
         this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor;
     return CupertinoDynamicColor.resolve(backgroundColor, context).alpha == 0xFF;
   }

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMediaQuery(context));
     final double bottomPadding = MediaQuery.of(context).padding.bottom;

     final Color backgroundColor = CupertinoDynamicColor.resolve(
       this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor,
       context,
     );

     BorderSide resolveBorderSide(BorderSide side) {
       return side == BorderSide.none
         ? side
         : side.copyWith(color: CupertinoDynamicColor.resolve(side.color, context));
     }

     // Return the border as is when it's a subclass.
     final Border? resolvedBorder = border == null || border.runtimeType != Border
       ? border
       : Border(
         top: resolveBorderSide(border!.top),
         left: resolveBorderSide(border!.left),
         bottom: resolveBorderSide(border!.bottom),
         right: resolveBorderSide(border!.right),
       );

     final Color inactive = CupertinoDynamicColor.resolve(inactiveColor, context);
     Widget result = DecoratedBox(
       decoration: BoxDecoration(
         border: resolvedBorder,
         color: backgroundColor,
       ),
       child: SizedBox(
         height: _kTabBarHeight + bottomPadding,
         child: IconTheme.merge( // Default with the inactive state.
           data: IconThemeData(color: inactive, size: iconSize),
           child: DefaultTextStyle( // Default with the inactive state.
             style: CupertinoTheme.of(context).textTheme.tabLabelTextStyle.copyWith(color: inactive),
             child: Padding(
               padding: EdgeInsets.only(bottom: bottomPadding),
               child: Semantics(
                 explicitChildNodes: true,
                 child: Row(
                   // Align bottom since we want the labels to be aligned.
                   crossAxisAlignment: CrossAxisAlignment.end,
                   children: _buildTabItems(context),
                 ),
               ),
             ),
           ),
         ),
       ),
     );

     if (!opaque(context)) {
       // For non-opaque backgrounds, apply a blur effect.
       result = ClipRect(
         child: BackdropFilter(
           filter: ImageFilter.blur(sigmaX: 10.0, sigmaY: 10.0),
           child: result,
         ),
       );
     }

     return result;
   }

   List<Widget> _buildTabItems(BuildContext context) {
     final List<Widget> result = <Widget>[];
     final CupertinoLocalizations localizations = CupertinoLocalizations.of(context);

     for (int index = 0; index < items.length; index += 1) {
       final bool active = index == currentIndex;
       result.add(
         _wrapActiveItem(
           context,
           Expanded(
             child: Semantics(
               selected: active,
               hint: localizations.tabSemanticsLabel(
                 tabIndex: index + 1,
                 tabCount: items.length,
               ),
               child: GestureDetector(
                 behavior: HitTestBehavior.opaque,
                 onTap: onTap == null ? null : () { onTap!(index); },
                 child: Padding(
                   padding: const EdgeInsets.only(bottom: 4.0),
                   child: Column(
                     mainAxisAlignment: MainAxisAlignment.end,
                     children: _buildSingleTabItem(items[index], active),
                   ),
                 ),
               ),
             ),
           ),
           active: active,
         ),
       );
     }

     return result;
   }

   List<Widget> _buildSingleTabItem(BottomNavigationBarItem item, bool active) {
     return <Widget>[
       Expanded(
         child: Center(child: active ? item.activeIcon : item.icon),
       ),
       if (item.label != null) Text(item.label!),
     ];
   }

   /// Change the active tab item's icon and title colors to active.
   Widget _wrapActiveItem(BuildContext context, Widget item, { required bool active }) {
     if (!active)
       return item;

     final Color activeColor = CupertinoDynamicColor.resolve(
       this.activeColor ?? CupertinoTheme.of(context).primaryColor,
       context,
     );
     return IconTheme.merge(
       data: IconThemeData(color: activeColor),
       child: DefaultTextStyle.merge(
         style: TextStyle(color: activeColor),
         child: item,
       ),
     );
   }

   /// Create a clone of the current [CupertinoTabBar] but with provided
   /// parameters overridden.
   CupertinoTabBar copyWith({
     Key? key,
     List<BottomNavigationBarItem>? items,
     Color? backgroundColor,
     Color? activeColor,
     Color? inactiveColor,
     double? iconSize,
     Border? border,
     int? currentIndex,
     ValueChanged<int>? onTap,
   }) {
     return CupertinoTabBar(
       key: key ?? this.key,
       items: items ?? this.items,
       backgroundColor: backgroundColor ?? this.backgroundColor,
       activeColor: activeColor ?? this.activeColor,
       inactiveColor: inactiveColor ?? this.inactiveColor,
       iconSize: iconSize ?? this.iconSize,
       border: border ?? this.border,
       currentIndex: currentIndex ?? this.currentIndex,
       onTap: onTap ?? this.onTap,
     );
   }
 }
	// 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 'dart:ui' show ImageFilter;

	import 'package:flutter/widgets.dart';

	import 'colors.dart';
	import 'localizations.dart';
	import 'theme.dart';

	// Standard iOS 10 tab bar height.
	const double _kTabBarHeight = 50.0;

	const Color _kDefaultTabBarBorderColor = CupertinoDynamicColor.withBrightness(
	color: Color(0x4C000000),
	darkColor: Color(0x29000000),
	);
	const Color _kDefaultTabBarInactiveColor = CupertinoColors.inactiveGray;

	/// An iOS-styled bottom navigation tab bar.
	///
	/// Displays multiple tabs using [BottomNavigationBarItem] with one tab being
	/// active, the first tab by default.
	///
	/// This [StatelessWidget] doesn't store the active tab itself. You must
	/// listen to the [onTap] callbacks and call `setState` with a new [currentIndex]
	/// for the new selection to reflect. This can also be done automatically
	/// by wrapping this with a [CupertinoTabScaffold].
	///
	/// Tab changes typically trigger a switch between [Navigator]s, each with its
	/// own navigation stack, per standard iOS design. This can be done by using
	/// [CupertinoTabView]s inside each tab builder in [CupertinoTabScaffold].
	///
	/// If the given [backgroundColor]'s opacity is not 1.0 (which is the case by
	/// default), it will produce a blurring effect to the content behind it.
	///
	/// When used as [CupertinoTabScaffold.tabBar], by default `CupertinoTabBar` has
	/// its text scale factor set to 1.0 and does not respond to text scale factor
	/// changes from the operating system, to match the native iOS behavior. To override
	/// this behavior, wrap each of the `navigationBar`'s components inside a [MediaQuery]
	/// with the desired [MediaQueryData.textScaleFactor] value. The text scale factor
	/// value from the operating system can be retrieved in many ways, such as querying
	/// [MediaQuery.textScaleFactorOf] against [CupertinoApp]'s [BuildContext].
	///
	/// {@tool dartpad}
	/// This example shows a [CupertinoTabBar] placed in a [CupertinoTabScaffold].
	///
	/// See code in examples/api/lib/cupertino/bottom_tab_bar/bottom_tab_bar.0.dart
	/// {@end-tool}
	///
	/// See also:
	///
	/// * [CupertinoTabScaffold], which hosts the [CupertinoTabBar] at the bottom.
	/// * [BottomNavigationBarItem], an item in a [CupertinoTabBar].
	class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
	/// Creates a tab bar in the iOS style.
	const CupertinoTabBar({
	Key? key,
	required this.items,
	this.onTap,
	this.currentIndex = 0,
	this.backgroundColor,
	this.activeColor,
	this.inactiveColor = _kDefaultTabBarInactiveColor,
	this.iconSize = 30.0,
	this.border = const Border(
	top: BorderSide(
	color: _kDefaultTabBarBorderColor,
	width: 0.0, // 0.0 means one physical pixel
	),
	),
	}) : assert(items != null),
	assert(
	items.length >= 2,
	"Tabs need at least 2 items to conform to Apple's HIG",
	),
	assert(currentIndex != null),
	assert(0 <= currentIndex && currentIndex < items.length),
	assert(iconSize != null),
	assert(inactiveColor != null),
	super(key: key);

	/// The interactive items laid out within the bottom navigation bar.
	///
	/// Must not be null.
	final List<BottomNavigationBarItem> items;

	/// The callback that is called when a item is tapped.
	///
	/// The widget creating the bottom navigation bar needs to keep track of the
	/// current index and call `setState` to rebuild it with the newly provided
	/// index.
	final ValueChanged<int>? onTap;

	/// The index into [items] of the current active item.
	///
	/// Must not be null and must inclusively be between 0 and the number of tabs
	/// minus 1.
	final int currentIndex;

	/// The background color of the tab bar. If it contains transparency, the
	/// tab bar will automatically produce a blurring effect to the content
	/// behind it.
	///
	/// Defaults to [CupertinoTheme]'s `barBackgroundColor` when null.
	final Color? backgroundColor;

	/// The foreground color of the icon and title for the [BottomNavigationBarItem]
	/// of the selected tab.
	///
	/// Defaults to [CupertinoTheme]'s `primaryColor` if null.
	final Color? activeColor;

	/// The foreground color of the icon and title for the [BottomNavigationBarItem]s
	/// in the unselected state.
	///
	/// Defaults to a [CupertinoDynamicColor] that matches the disabled foreground
	/// color of the native `UITabBar` component. Cannot be null.
	final Color inactiveColor;

	/// The size of all of the [BottomNavigationBarItem] icons.
	///
	/// This value is used to configure the [IconTheme] for the navigation bar.
	/// When a [BottomNavigationBarItem.icon] widget is not an [Icon] the widget
	/// should configure itself to match the icon theme's size and color.
	///
	/// Must not be null.
	final double iconSize;

	/// The border of the [CupertinoTabBar].
	///
	/// The default value is a one physical pixel top border with grey color.
	final Border? border;

	@override
	Size get preferredSize => const Size.fromHeight(_kTabBarHeight);

	/// Indicates whether the tab bar is fully opaque or can have contents behind
	/// it show through it.
	bool opaque(BuildContext context) {
	final Color backgroundColor =
	this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor;
	return CupertinoDynamicColor.resolve(backgroundColor, context).alpha == 0xFF;
	}

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMediaQuery(context));
	final double bottomPadding = MediaQuery.of(context).padding.bottom;

	final Color backgroundColor = CupertinoDynamicColor.resolve(
	this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor,
	context,
	);

	BorderSide resolveBorderSide(BorderSide side) {
	return side == BorderSide.none
	? side
	: side.copyWith(color: CupertinoDynamicColor.resolve(side.color, context));
	}

	// Return the border as is when it's a subclass.
	final Border? resolvedBorder = border == null \|\| border.runtimeType != Border
	? border
	: Border(
	top: resolveBorderSide(border!.top),
	left: resolveBorderSide(border!.left),
	bottom: resolveBorderSide(border!.bottom),
	right: resolveBorderSide(border!.right),
	);

	final Color inactive = CupertinoDynamicColor.resolve(inactiveColor, context);
	Widget result = DecoratedBox(
	decoration: BoxDecoration(
	border: resolvedBorder,
	color: backgroundColor,
	),
	child: SizedBox(
	height: _kTabBarHeight + bottomPadding,
	child: IconTheme.merge( // Default with the inactive state.
	data: IconThemeData(color: inactive, size: iconSize),
	child: DefaultTextStyle( // Default with the inactive state.
	style: CupertinoTheme.of(context).textTheme.tabLabelTextStyle.copyWith(color: inactive),
	child: Padding(
	padding: EdgeInsets.only(bottom: bottomPadding),
	child: Semantics(
	explicitChildNodes: true,
	child: Row(
	// Align bottom since we want the labels to be aligned.
	crossAxisAlignment: CrossAxisAlignment.end,
	children: _buildTabItems(context),
	),
	),
	),
	),
	),
	),
	);

	if (!opaque(context)) {
	// For non-opaque backgrounds, apply a blur effect.
	result = ClipRect(
	child: BackdropFilter(
	filter: ImageFilter.blur(sigmaX: 10.0, sigmaY: 10.0),
	child: result,
	),
	);
	}

	return result;
	}

	List<Widget> _buildTabItems(BuildContext context) {
	final List<Widget> result = <Widget>[];
	final CupertinoLocalizations localizations = CupertinoLocalizations.of(context);

	for (int index = 0; index < items.length; index += 1) {
	final bool active = index == currentIndex;
	result.add(
	_wrapActiveItem(
	context,
	Expanded(
	child: Semantics(
	selected: active,
	hint: localizations.tabSemanticsLabel(
	tabIndex: index + 1,
	tabCount: items.length,
	),
	child: GestureDetector(
	behavior: HitTestBehavior.opaque,
	onTap: onTap == null ? null : () { onTap!(index); },
	child: Padding(
	padding: const EdgeInsets.only(bottom: 4.0),
	child: Column(
	mainAxisAlignment: MainAxisAlignment.end,
	children: _buildSingleTabItem(items[index], active),
	),
	),
	),
	),
	),
	active: active,
	),
	);
	}

	return result;
	}

	List<Widget> _buildSingleTabItem(BottomNavigationBarItem item, bool active) {
	return <Widget>[
	Expanded(
	child: Center(child: active ? item.activeIcon : item.icon),
	),
	if (item.label != null) Text(item.label!),
	];
	}

	/// Change the active tab item's icon and title colors to active.
	Widget _wrapActiveItem(BuildContext context, Widget item, { required bool active }) {
	if (!active)
	return item;

	final Color activeColor = CupertinoDynamicColor.resolve(
	this.activeColor ?? CupertinoTheme.of(context).primaryColor,
	context,
	);
	return IconTheme.merge(
	data: IconThemeData(color: activeColor),
	child: DefaultTextStyle.merge(
	style: TextStyle(color: activeColor),
	child: item,
	),
	);
	}

	/// Create a clone of the current [CupertinoTabBar] but with provided
	/// parameters overridden.
	CupertinoTabBar copyWith({
	Key? key,
	List<BottomNavigationBarItem>? items,
	Color? backgroundColor,
	Color? activeColor,
	Color? inactiveColor,
	double? iconSize,
	Border? border,
	int? currentIndex,
	ValueChanged<int>? onTap,
	}) {
	return CupertinoTabBar(
	key: key ?? this.key,
	items: items ?? this.items,
	backgroundColor: backgroundColor ?? this.backgroundColor,
	activeColor: activeColor ?? this.activeColor,
	inactiveColor: inactiveColor ?? this.inactiveColor,
	iconSize: iconSize ?? this.iconSize,
	border: border ?? this.border,
	currentIndex: currentIndex ?? this.currentIndex,
	onTap: onTap ?? this.onTap,
	);
	}
	}