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added MaterialStateColor support to TabBarTheme.labelColor (#109541)
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@werainkhatri
werainkhatri authored Feb 15, 2023
1 parent d29668d commit 378668d
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6 changes: 6 additions & 0 deletions packages/flutter/lib/src/material/tab_bar_theme.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,12 @@ class TabBarTheme with Diagnosticable {
final Color? dividerColor;

/// Overrides the default value for [TabBar.labelColor].
///
/// If [labelColor] is a [MaterialStateColor], then the effective color will
/// depend on the [MaterialState.selected] state, i.e. if the [Tab] is
/// selected or not. In case of unselected state, this [MaterialStateColor]'s
/// resolved color will be used even if [TabBar.unselectedLabelColor] or
/// [unselectedLabelColor] is non-null.
final Color? labelColor;

/// Overrides the default value for [TabBar.labelPadding].
Expand Down
131 changes: 96 additions & 35 deletions packages/flutter/lib/src/material/tabs.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ class Tab extends StatelessWidget implements PreferredSizeWidget {
class _TabStyle extends AnimatedWidget {
const _TabStyle({
required Animation<double> animation,
required this.selected,
required this.isSelected,
required this.labelColor,
required this.unselectedLabelColor,
required this.labelStyle,
Expand All @@ -176,18 +176,58 @@ class _TabStyle extends AnimatedWidget {

final TextStyle? labelStyle;
final TextStyle? unselectedLabelStyle;
final bool selected;
final bool isSelected;
final Color? labelColor;
final Color? unselectedLabelColor;
final Widget child;

MaterialStateColor _resolveWithLabelColor(BuildContext context) {
final ThemeData themeData = Theme.of(context);
final TabBarTheme tabBarTheme = TabBarTheme.of(context);
final TabBarTheme defaults = themeData.useMaterial3 ? _TabsDefaultsM3(context) : _TabsDefaultsM2(context);
final Animation<double> animation = listenable as Animation<double>;

// labelStyle.color (and tabBarTheme.labelStyle.color) is not considered
// as it'll be a breaking change without a possible migration plan. for
// details: https://github.com/flutter/flutter/pull/109541#issuecomment-1294241417
Color selectedColor = labelColor
?? tabBarTheme.labelColor
?? defaults.labelColor!;

final Color unselectedColor;

if (selectedColor is MaterialStateColor) {
unselectedColor = selectedColor.resolve(const <MaterialState>{});
selectedColor = selectedColor.resolve(const <MaterialState>{MaterialState.selected});
} else {
// unselectedLabelColor and tabBarTheme.unselectedLabelColor are ignored
// when labelColor is a MaterialStateColor.
unselectedColor = unselectedLabelColor
?? tabBarTheme.unselectedLabelColor
?? (themeData.useMaterial3
? defaults.unselectedLabelColor!
: selectedColor.withAlpha(0xB2)); // 70% alpha
}

return MaterialStateColor.resolveWith((Set<MaterialState> states) {
if (states.contains(MaterialState.selected)) {
return Color.lerp(selectedColor, unselectedColor, animation.value)!;
}
return Color.lerp(unselectedColor, selectedColor, animation.value)!;
});
}

@override
Widget build(BuildContext context) {
final ThemeData themeData = Theme.of(context);
final TabBarTheme tabBarTheme = TabBarTheme.of(context);
final TabBarTheme defaults = themeData.useMaterial3 ? _TabsDefaultsM3(context) : _TabsDefaultsM2(context);
final Animation<double> animation = listenable as Animation<double>;

final Set<MaterialState> states = isSelected
? const <MaterialState>{MaterialState.selected}
: const <MaterialState>{};

// To enable TextStyle.lerp(style1, style2, value), both styles must have
// the same value of inherit. Force that to be inherit=true here.
final TextStyle defaultStyle = (labelStyle
Expand All @@ -199,21 +239,10 @@ class _TabStyle extends AnimatedWidget {
?? labelStyle
?? defaults.unselectedLabelStyle!
).copyWith(inherit: true);
final TextStyle textStyle = selected
final TextStyle textStyle = isSelected
? TextStyle.lerp(defaultStyle, defaultUnselectedStyle, animation.value)!
: TextStyle.lerp(defaultUnselectedStyle, defaultStyle, animation.value)!;

final Color selectedColor = labelColor
?? tabBarTheme.labelColor
?? defaults.labelColor!;
final Color unselectedColor = unselectedLabelColor
?? tabBarTheme.unselectedLabelColor
?? (themeData.useMaterial3
? defaults.unselectedLabelColor!
: selectedColor.withAlpha(0xB2)); // 70% alpha
final Color color = selected
? Color.lerp(selectedColor, unselectedColor, animation.value)!
: Color.lerp(unselectedColor, selectedColor, animation.value)!;
final Color color = _resolveWithLabelColor(context).resolve(states);

return DefaultTextStyle(
style: textStyle.copyWith(color: color),
Expand Down Expand Up @@ -738,7 +767,8 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
///
/// If [automaticIndicatorColorAdjustment] is true,
/// then the [indicatorColor] will be automatically adjusted to [Colors.white]
/// when the [indicatorColor] is same as [Material.color] of the [Material] parent widget.
/// when the [indicatorColor] is same as [Material.color] of the [Material]
/// parent widget.
final bool automaticIndicatorColorAdjustment;

/// Defines how the selected tab indicator's size is computed.
Expand All @@ -762,23 +792,50 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {

/// The color of selected tab labels.
///
/// If [ThemeData.useMaterial3] is false, unselected tab labels are rendered with
/// the same color with 70% opacity unless [unselectedLabelColor] is non-null.
///
/// If this property is null and [ThemeData.useMaterial3] is true, [ColorScheme.primary]
/// will be used, otherwise the color of the [ThemeData.primaryTextTheme]'s
/// If null, then [TabBarTheme.labelColor] is used. If that is also null and
/// [ThemeData.useMaterial3] is true, [ColorScheme.primary] will be used,
/// otherwise the color of the [ThemeData.primaryTextTheme]'s
/// [TextTheme.bodyLarge] text color is used.
///
/// If [labelColor] (or, if null, [TabBarTheme.labelColor]) is a
/// [MaterialStateColor], then the effective tab color will depend on the
/// [MaterialState.selected] state, i.e. if the [Tab] is selected or not,
/// ignoring [unselectedLabelColor] even if it's non-null.
///
/// Note: [labelStyle]'s color and [TabBarTheme.labelStyle]'s color do not
/// affect the effective [labelColor].
///
/// See also:
///
/// * [unselectedLabelColor], for color of unselected tab labels.
final Color? labelColor;

/// The color of unselected tab labels.
///
/// If this property is null and [ThemeData.useMaterial3] is true, [ColorScheme.onSurfaceVariant]
/// will be used, otherwise unselected tab labels are rendered with the
/// [labelColor] with 70% opacity.
/// If [labelColor] (or, if null, [TabBarTheme.labelColor]) is a
/// [MaterialStateColor], then the unselected tabs are rendered with
/// that [MaterialStateColor]'s resolved color for unselected state, even if
/// [unselectedLabelColor] is non-null.
///
/// If null, then [TabBarTheme.unselectedLabelColor] is used. If that is also
/// null and [ThemeData.useMaterial3] is true, [ColorScheme.onSurfaceVariant]
/// will be used, otherwise unselected tab labels are rendered with
/// [labelColor] at 70% opacity.
///
/// Note: [unselectedLabelStyle]'s color and
/// [TabBarTheme.unselectedLabelStyle]'s color are ignored in
/// [unselectedLabelColor]'s precedence calculation.
///
/// See also:
///
/// * [labelColor], for color of selected tab labels.
final Color? unselectedLabelColor;

/// The text style of the selected tab labels.
///
/// This does not influence color of the tab labels even if [TextStyle.color]
/// is non-null. Refer [labelColor] to color selected tab labels instead.
///
/// If [unselectedLabelStyle] is null, then this text style will be used for
/// both selected and unselected label styles.
///
Expand All @@ -787,6 +844,18 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
/// [TextTheme.bodyLarge] definition is used.
final TextStyle? labelStyle;

/// The text style of the unselected tab labels.
///
/// This does not influence color of the tab labels even if [TextStyle.color]
/// is non-null. Refer [unselectedLabelColor] to color unselected tab labels
/// instead.
///
/// If this property is null and [ThemeData.useMaterial3] is true,
/// [TextTheme.titleSmall] will be used, otherwise then the [labelStyle] value
/// is used. If [labelStyle] is null, the text style of the
/// [ThemeData.primaryTextTheme]'s [TextTheme.bodyLarge] definition is used.
final TextStyle? unselectedLabelStyle;

/// The padding added to each of the tab labels.
///
/// If there are few tabs with both icon and text and few
Expand All @@ -796,14 +865,6 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
/// If this property is null, then kTabLabelPadding is used.
final EdgeInsetsGeometry? labelPadding;

/// The text style of the unselected tab labels.
///
/// If this property is null and [ThemeData.useMaterial3] is true, [TextTheme.titleSmall]
/// will be used, otherwise then the [labelStyle] value is used. If [labelStyle]
/// is null, the text style of the [ThemeData.primaryTextTheme]'s
/// [TextTheme.bodyLarge] definition is used.
final TextStyle? unselectedLabelStyle;

/// Defines the ink response focus, hover, and splash colors.
///
/// If non-null, it is resolved against one of [MaterialState.focused],
Expand Down Expand Up @@ -1209,10 +1270,10 @@ class _TabBarState extends State<TabBar> {
widget.onTap?.call(index);
}

Widget _buildStyledTab(Widget child, bool selected, Animation<double> animation) {
Widget _buildStyledTab(Widget child, bool isSelected, Animation<double> animation) {
return _TabStyle(
animation: animation,
selected: selected,
isSelected: isSelected,
labelColor: widget.labelColor,
unselectedLabelColor: widget.unselectedLabelColor,
labelStyle: widget.labelStyle,
Expand Down Expand Up @@ -1368,7 +1429,7 @@ class _TabBarState extends State<TabBar> {
painter: _indicatorPainter,
child: _TabStyle(
animation: kAlwaysDismissedAnimation,
selected: false,
isSelected: false,
labelColor: widget.labelColor,
unselectedLabelColor: widget.unselectedLabelColor,
labelStyle: widget.labelStyle,
Expand Down
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