[Material] Fix BottomNavTheme.showSelectedLabels bug (#67342)

packages/flutter/lib/src/material/bottom_navigation_bar.dart

@@ -140,7 +140,7 @@ class BottomNavigationBar extends StatefulWidget {
   /// Creates a bottom navigation bar which is typically used as a
   /// [Scaffold]'s [Scaffold.bottomNavigationBar] argument.
   ///
-  /// The length of [items] must be at least two and each item's icon and title
+  /// The length of [items] must be at least two and each item's icon and label
   /// must not be null.
   ///
   /// If [type] is null then [BottomNavigationBarType.fixed] is used when there
@@ -164,10 +164,14 @@ class BottomNavigationBar extends StatefulWidget {
   /// former is preferred, [fixedColor] only exists for the sake of
   /// backwards compatibility.
   ///
-  /// The [showSelectedLabels] argument must be non-null.
+  /// If [showSelectedLabels] is `null`, [BottomNavigationBarThemeData.showSelectedLabels]
+  /// is used. If [BottomNavigationBarThemeData.showSelectedLabels]  is null,
+  /// then [showSelectedLabels] defaults to `true`.
   ///
-  /// The [showUnselectedLabels] argument defaults to `true` if [type] is
-  /// [BottomNavigationBarType.fixed] and `false` if [type] is
+  /// If [showUnselectedLabels] is `null`, [BottomNavigationBarThemeData.showUnselectedLabels]
+  /// is used. If [BottomNavigationBarThemeData.showSelectedLabels] is null,
+  /// then [showUnselectedLabels] defaults to `true` when [type] is
+  /// [BottomNavigationBarType.fixed] and `false` when [type] is
   /// [BottomNavigationBarType.shifting].
   BottomNavigationBar({
     Key? key,
@@ -187,7 +191,7 @@ class BottomNavigationBar extends StatefulWidget {
     this.unselectedFontSize = 12.0,
     this.selectedLabelStyle,
     this.unselectedLabelStyle,
-    this.showSelectedLabels = true,
+    this.showSelectedLabels,
     this.showUnselectedLabels,
     this.mouseCursor,
   }) : assert(items != null),
@@ -206,7 +210,6 @@ class BottomNavigationBar extends StatefulWidget {
        ),
        assert(selectedFontSize != null && selectedFontSize >= 0.0),
        assert(unselectedFontSize != null && unselectedFontSize >= 0.0),
-       assert(showSelectedLabels != null),
        selectedItemColor = selectedItemColor ?? fixedColor,
        super(key: key);
 
@@ -286,7 +289,7 @@ class BottomNavigationBar extends StatefulWidget {
   ///
   /// It this field is provided, it must contain non-null [IconThemeData.size]
   /// and [IconThemeData.color] properties. Also, if this field is supplied,
-  /// [unselectedIconTheme] must be provided.
+  /// [selectedIconTheme] must be provided.
   final IconThemeData? unselectedIconTheme;
 
   /// The [TextStyle] of the [BottomNavigationBarItem] labels when they are
@@ -318,7 +321,7 @@ class BottomNavigationBar extends StatefulWidget {
   final bool? showUnselectedLabels;
 
   /// Whether the labels are shown for the selected [BottomNavigationBarItem].
-  final bool showSelectedLabels;
+  final bool? showSelectedLabels;
 
   /// The cursor for a mouse pointer when it enters or is hovering over the
   /// tiles.
@@ -346,8 +349,8 @@ class _BottomNavigationTile extends StatelessWidget {
     required this.unselectedLabelStyle,
     required this.selectedIconTheme,
     required this.unselectedIconTheme,
-    this.showSelectedLabels,
-    this.showUnselectedLabels,
+    required this.showSelectedLabels,
+    required this.showUnselectedLabels,
     this.indexLabel,
     required this.mouseCursor,
     }) : assert(type != null),
@@ -371,8 +374,8 @@ class _BottomNavigationTile extends StatelessWidget {
   final TextStyle selectedLabelStyle;
   final TextStyle unselectedLabelStyle;
   final String? indexLabel;
-  final bool? showSelectedLabels;
-  final bool? showUnselectedLabels;
+  final bool showSelectedLabels;
+  final bool showUnselectedLabels;
   final MouseCursor mouseCursor;
 
   @override
@@ -383,16 +386,10 @@ class _BottomNavigationTile extends StatelessWidget {
     // (which is an integer) by a large number.
     final int size;
 
-    final BottomNavigationBarThemeData bottomTheme = BottomNavigationBarTheme.of(context);
-
     final double selectedFontSize = selectedLabelStyle.fontSize!;
 
-    final double selectedIconSize = selectedIconTheme?.size
-      ?? bottomTheme.selectedIconTheme?.size
-      ?? iconSize;
-    final double unselectedIconSize = unselectedIconTheme?.size
-      ?? bottomTheme.unselectedIconTheme?.size
-      ?? iconSize;
+    final double selectedIconSize = selectedIconTheme?.size ?? iconSize;
+    final double unselectedIconSize = unselectedIconTheme?.size ?? iconSize;
 
     // The amount that the selected icon is bigger than the unselected icons,
     // (or zero if the selected icon is not bigger than the unselected icons).
@@ -418,9 +415,9 @@ class _BottomNavigationTile extends StatelessWidget {
     // | text
     // |      <-- Padding equal to 1/2 text height + 1/2 unselectedIconDiff.
     // =======
-    final double bottomPadding;
-    final double topPadding;
-    if (showSelectedLabels! && !showUnselectedLabels!) {
+    double bottomPadding;
+    double topPadding;
+    if (showSelectedLabels && !showUnselectedLabels) {
       bottomPadding = Tween<double>(
         begin: selectedIconDiff / 2.0,
         end: selectedFontSize / 2.0 - unselectedIconDiff / 2.0,
@@ -429,7 +426,7 @@ class _BottomNavigationTile extends StatelessWidget {
         begin: selectedFontSize + selectedIconDiff / 2.0,
         end: selectedFontSize / 2.0 - unselectedIconDiff / 2.0,
       ).evaluate(animation);
-    } else if (!showSelectedLabels! && !showUnselectedLabels!) {
+    } else if (!showSelectedLabels && !showUnselectedLabels) {
       bottomPadding = Tween<double>(
         begin: selectedIconDiff / 2.0,
         end: unselectedIconDiff / 2.0,
@@ -474,8 +471,8 @@ class _BottomNavigationTile extends StatelessWidget {
               iconSize: iconSize,
               selected: selected,
               item: item,
-              selectedIconTheme: selectedIconTheme ?? bottomTheme.selectedIconTheme,
-              unselectedIconTheme: unselectedIconTheme ?? bottomTheme.unselectedIconTheme,
+              selectedIconTheme: selectedIconTheme,
+              unselectedIconTheme: unselectedIconTheme,
             ),
             _Label(
               colorTween: colorTween!,
@@ -483,8 +480,8 @@ class _BottomNavigationTile extends StatelessWidget {
               item: item,
               selectedLabelStyle: selectedLabelStyle,
               unselectedLabelStyle: unselectedLabelStyle,
-              showSelectedLabels: showSelectedLabels ?? bottomTheme.showUnselectedLabels!,
-              showUnselectedLabels: showUnselectedLabels ?? bottomTheme.showUnselectedLabels!,
+              showSelectedLabels: showSelectedLabels,
+              showUnselectedLabels: showUnselectedLabels,
             ),
           ],
         ),
@@ -894,7 +891,7 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
         colorTween: colorTween,
         flex: _evaluateFlex(_animations[i]),
         selected: i == widget.currentIndex,
-        showSelectedLabels: widget.showSelectedLabels,
+        showSelectedLabels: widget.showSelectedLabels ?? bottomTheme.showSelectedLabels ?? true,
         showUnselectedLabels: widget.showUnselectedLabels ?? bottomTheme.showUnselectedLabels ?? _defaultShowUnselected,
         indexLabel: localizations.tabLabel(tabIndex: i + 1, tabCount: widget.items.length),
         mouseCursor: effectiveMouseCursor,

packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart

@@ -58,12 +58,20 @@ class BottomNavigationBarThemeData with Diagnosticable {
   /// The size, opacity, and color of the icon in the currently selected
   /// [BottomNavigationBarItem.icon].
   ///
+  /// If [BottomNavigationBar.selectedIconTheme] is non-null on the widget,
+  /// the whole [IconThemeData] from the widget will be used over this
+  /// [selectedIconTheme].
+  ///
   /// See [BottomNavigationBar.selectedIconTheme].
   final IconThemeData? selectedIconTheme;
 
   /// The size, opacity, and color of the icon in the currently unselected
   /// [BottomNavigationBarItem.icon]s.
   ///
+  /// If [BottomNavigationBar.unselectedIconTheme] is non-null on the widget,
+  /// the whole [IconThemeData] from the widget will be used over this
+  /// [unselectedIconTheme].
+  ///
   /// See [BottomNavigationBar.unselectedIconTheme].
   final IconThemeData? unselectedIconTheme;
 

packages/flutter/test/material/bottom_navigation_bar_theme_test.dart

@@ -258,6 +258,119 @@ void main() {
     expect(_material(tester).elevation, equals(elevation));
     expect(_material(tester).color, equals(backgroundColor));
   });
+
+  testWidgets('BottomNavigationBarTheme can be used to hide all labels', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/66738.
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          bottomNavigationBarTheme: const BottomNavigationBarThemeData(
+            showSelectedLabels: false,
+            showUnselectedLabels: false,
+          ),
+        ),
+        home: Scaffold(
+          bottomNavigationBar: BottomNavigationBar(
+            items: const <BottomNavigationBarItem>[
+              BottomNavigationBarItem(
+                icon: Icon(Icons.ac_unit),
+                label: 'AC',
+              ),
+              BottomNavigationBarItem(
+                icon: Icon(Icons.access_alarm),
+                label: 'Alarm',
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+
+    final Finder findOpacity = find.descendant(
+      of: find.byType(BottomNavigationBar),
+      matching: find.byType(Opacity),
+    );
+
+    expect(findOpacity, findsNWidgets(2));
+    expect(tester.widget<Opacity>(findOpacity.at(0)).opacity, 0.0);
+    expect(tester.widget<Opacity>(findOpacity.at(1)).opacity, 0.0);
+  });
+
+  testWidgets('BottomNavigationBarTheme can be used to hide selected labels', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/66738.
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          bottomNavigationBarTheme: const BottomNavigationBarThemeData(
+            showSelectedLabels: false,
+            showUnselectedLabels: true,
+          ),
+        ),
+        home: Scaffold(
+          bottomNavigationBar: BottomNavigationBar(
+            items: const <BottomNavigationBarItem>[
+              BottomNavigationBarItem(
+                icon: Icon(Icons.ac_unit),
+                label: 'AC',
+              ),
+              BottomNavigationBarItem(
+                icon: Icon(Icons.access_alarm),
+                label: 'Alarm',
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+
+    final Finder findFadeTransition = find.descendant(
+      of: find.byType(BottomNavigationBar),
+      matching: find.byType(FadeTransition),
+    );
+
+    expect(findFadeTransition, findsNWidgets(2));
+    expect(tester.widget<FadeTransition>(findFadeTransition.at(0)).opacity.value, 0.0);
+    expect(tester.widget<FadeTransition>(findFadeTransition.at(1)).opacity.value, 1.0);
+  });
+
+  testWidgets('BottomNavigationBarTheme can be used to hide unselected labels', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          bottomNavigationBarTheme: const BottomNavigationBarThemeData(
+            showSelectedLabels: true,
+            showUnselectedLabels: false,
+          ),
+        ),
+        home: Scaffold(
+          bottomNavigationBar: BottomNavigationBar(
+            items: const <BottomNavigationBarItem>[
+              BottomNavigationBarItem(
+                icon: Icon(Icons.ac_unit),
+                label: 'AC',
+              ),
+              BottomNavigationBarItem(
+                icon: Icon(Icons.access_alarm),
+                label: 'Alarm',
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+
+    final Finder findFadeTransition = find.descendant(
+      of: find.byType(BottomNavigationBar),
+      matching: find.byType(FadeTransition),
+    );
+
+    expect(findFadeTransition, findsNWidgets(2));
+    expect(tester.widget<FadeTransition>(findFadeTransition.at(0)).opacity.value, 1.0);
+    expect(tester.widget<FadeTransition>(findFadeTransition.at(1)).opacity.value, 0.0);
+  });
 }
 
 TextStyle _iconStyle(WidgetTester tester, IconData icon) {