ButtonTheme.of().colorScheme defers to Theme (#22880)

ButtonThemeData no longer requires a colorScheme. If colorScheme is null, ButtonTheme.of() will initialize it from the current Theme.

examples/flutter_gallery/lib/demo/material/cards_demo.dart

@@ -129,7 +129,6 @@ class TravelDestinationItem extends StatelessWidget {
               ),
               // share, explore buttons
               ButtonTheme.bar(
-                colorScheme: theme.colorScheme,
                 child: ButtonBar(
                   alignment: MainAxisAlignment.start,
                   children: <Widget>[

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

@@ -80,7 +80,7 @@ class ButtonTheme extends InheritedWidget {
     Color disabledColor,
     Color highlightColor,
     Color splashColor,
-    ColorScheme colorScheme = const ColorScheme.light(),
+    ColorScheme colorScheme,
     MaterialTapTargetSize materialTapTargetSize,
     Widget child,
   }) : assert(textTheme != null),
@@ -88,7 +88,6 @@ class ButtonTheme extends InheritedWidget {
        assert(height != null && height >= 0.0),
        assert(alignedDropdown != null),
        assert(layoutBehavior != null),
-       assert(colorScheme != null),
        data = ButtonThemeData(
          textTheme: textTheme,
          minWidth: minWidth,
@@ -142,14 +141,13 @@ class ButtonTheme extends InheritedWidget {
     Color disabledColor,
     Color highlightColor,
     Color splashColor,
-    ColorScheme colorScheme = const ColorScheme.light(),
+    ColorScheme colorScheme,
     Widget child,
     ButtonBarLayoutBehavior layoutBehavior = ButtonBarLayoutBehavior.padded,
   }) : assert(textTheme != null),
        assert(minWidth != null && minWidth >= 0.0),
        assert(height != null && height >= 0.0),
        assert(alignedDropdown != null),
-       assert(colorScheme != null),
        data = ButtonThemeData(
          textTheme: textTheme,
          minWidth: minWidth,
@@ -177,8 +175,19 @@ class ButtonTheme extends InheritedWidget {
   /// ButtonThemeData theme = ButtonTheme.of(context);
   /// ```
   static ButtonThemeData of(BuildContext context) {
-    final ButtonTheme result = context.inheritFromWidgetOfExactType(ButtonTheme);
-    return result?.data ?? Theme.of(context).buttonTheme;
+    final ButtonTheme inheritedButtonTheme = context.inheritFromWidgetOfExactType(ButtonTheme);
+    ButtonThemeData buttonTheme = inheritedButtonTheme?.data;
+    if (buttonTheme?.colorScheme == null) { // if buttonTheme or buttonTheme.colorScheme is null
+      final ThemeData theme = Theme.of(context);
+      buttonTheme ??= theme.buttonTheme;
+      if (buttonTheme.colorScheme == null) {
+        buttonTheme = buttonTheme.copyWith(
+          colorScheme: theme.buttonTheme.colorScheme ?? theme.colorScheme,
+        );
+        assert(buttonTheme.colorScheme != null);
+      }
+    }
+    return buttonTheme;
   }
 
   @override
@@ -194,7 +203,9 @@ class ButtonThemeData extends Diagnosticable {
   /// Create a button theme object that can be used with [ButtonTheme]
   /// or [ThemeData].
   ///
-  /// The [textTheme], [minWidth], and [height] parameters must not be null.
+  /// The [textTheme], [minWidth], [height], [alignedDropDown], and
+  /// [layoutBehavior] parameters must not be null. The [minWidth] and
+  /// [height] parameters must greater than or equal to zero.
   ///
   /// The ButtonTheme's methods that have a [MaterialButton] parameter and
   /// have a name with a `get` prefix are used by [RaisedButton],
@@ -211,14 +222,13 @@ class ButtonThemeData extends Diagnosticable {
     Color disabledColor,
     Color highlightColor,
     Color splashColor,
-    this.colorScheme = const ColorScheme.light(),
+    this.colorScheme,
     MaterialTapTargetSize materialTapTargetSize,
   }) : assert(textTheme != null),
        assert(minWidth != null && minWidth >= 0.0),
        assert(height != null && height >= 0.0),
        assert(alignedDropdown != null),
        assert(layoutBehavior != null),
-       assert(colorScheme != null),
        _buttonColor = buttonColor,
        _disabledColor = disabledColor,
        _highlightColor = highlightColor,
@@ -719,6 +729,7 @@ class ButtonThemeData extends Diagnosticable {
   /// replaced with the non-null parameter values.
   ButtonThemeData copyWith({
     ButtonTextTheme textTheme,
+    ButtonBarLayoutBehavior layoutBehavior,
     double minWidth,
     double height,
     EdgeInsetsGeometry padding,
@@ -733,6 +744,7 @@ class ButtonThemeData extends Diagnosticable {
   }) {
     return ButtonThemeData(
       textTheme: textTheme ?? this.textTheme,
+      layoutBehavior: layoutBehavior ?? this.layoutBehavior,
       minWidth: minWidth ?? this.minWidth,
       height: height ?? this.height,
       padding: padding ?? this.padding,

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

@@ -952,7 +952,6 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
       ),
     );
     final Widget actions = ButtonTheme.bar(
-      colorScheme: theme.buttonTheme.colorScheme,
       child: ButtonBar(
         children: <Widget>[
           FlatButton(

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

@@ -274,7 +274,6 @@ class AlertDialog extends StatelessWidget {
 
     if (actions != null) {
       children.add(ButtonTheme.bar(
-        colorScheme: Theme.of(context).colorScheme,
         child: ButtonBar(
           children: actions,
         ),

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

@@ -400,7 +400,6 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
                   opacity: 0.54
                 ),
                 child: ButtonTheme.bar(
-                  colorScheme: themeData.colorScheme,
                   child: Ink(
                     height: 64.0,
                     color: _selectedRowCount > 0 ? themeData.secondaryHeaderColor : null,

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

@@ -1605,7 +1605,6 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
           ),
           child: SafeArea(
             child: ButtonTheme.bar(
-              colorScheme: themeData.colorScheme,
               child: SafeArea(
                 top: false,
                 child: ButtonBar(

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

@@ -213,7 +213,6 @@ class SnackBar extends StatelessWidget {
     ];
     if (action != null) {
       children.add(ButtonTheme.bar(
-        colorScheme: theme.colorScheme,
         padding: const EdgeInsets.symmetric(horizontal: _kSnackBarPadding),
         textTheme: ButtonTextTheme.accent,
         child: action,

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

@@ -1541,7 +1541,6 @@ class _TimePickerDialogState extends State<_TimePickerDialog> {
     );
 
     final Widget actions = ButtonTheme.bar(
-      colorScheme: theme.colorScheme,
       child: ButtonBar(
         children: <Widget>[
           FlatButton(

packages/flutter/test/material/button_bar_test.dart

@@ -64,4 +64,56 @@ void main() {
     final Finder buttonBar = find.byType(ButtonBar);
     expect(tester.getBottomRight(buttonBar).dy - tester.getTopRight(buttonBar).dy, 26.0);
   });
+
+  testWidgets('ButtonBar FlatButton inherits Theme accentColor', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/22789
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(accentColor: const Color(1)),
+        home: Builder(
+          builder: (BuildContext context) {
+            return Center(
+              child: ButtonTheme.bar(
+                child: ButtonBar(
+                  children: <Widget>[
+                    FlatButton(
+                      child: const Text('button'),
+                      onPressed: () {
+                        showDialog<void>(
+                          context: context,
+                          builder: (BuildContext context) {
+                            return AlertDialog( // puts its actions in a ButtonBar
+                              actions: <Widget>[
+                                FlatButton(
+                                  onPressed: () { },
+                                  child: const Text('enabled'),
+                                ),
+                              ],
+                            );
+                          },
+                        );
+                      },
+                    ),
+                  ],
+                ),
+              ),
+            );
+          },
+        ),
+      ),
+    );
+
+    expect(tester.widget<RawMaterialButton>(find.byType(RawMaterialButton)).textStyle.color, const Color(1));
+
+    // Show the dialog
+    await tester.tap(find.text('button'));
+    await tester.pumpAndSettle();
+
+    final Finder dialogButton = find.ancestor(
+      of: find.text('enabled'),
+      matching: find.byType(RawMaterialButton),
+    );
+    expect(tester.widget<RawMaterialButton>(dialogButton).textStyle.color, const Color(1));
+  });
 }

packages/flutter/test/material/button_theme_test.dart

@@ -36,9 +36,12 @@ void main() {
 
   testWidgets('ButtonTheme defaults', (WidgetTester tester) async {
     ButtonTextTheme textTheme;
+    ButtonBarLayoutBehavior layoutBehavior;
     BoxConstraints constraints;
     EdgeInsets padding;
     ShapeBorder shape;
+    bool alignedDropdown;
+    ColorScheme colorScheme;
 
     await tester.pumpWidget(
       ButtonTheme(
@@ -49,13 +52,16 @@ void main() {
             constraints = theme.constraints;
             padding = theme.padding;
             shape = theme.shape;
+            layoutBehavior = theme.layoutBehavior;
+            colorScheme = theme.colorScheme;
+            alignedDropdown = theme.alignedDropdown;
             return Container(
               alignment: Alignment.topLeft,
-              child: const Directionality(
+              child: Directionality(
                 textDirection: TextDirection.ltr,
                 child: FlatButton(
-                  onPressed: null,
-                  child: Text('b'), // intrinsic width < minimum width
+                  onPressed: () { },
+                  child: const Text('b'), // intrinsic width < minimum width
                 ),
               ),
             );
@@ -65,12 +71,14 @@ void main() {
     );
 
     expect(textTheme, ButtonTextTheme.normal);
+    expect(layoutBehavior, ButtonBarLayoutBehavior.padded);
     expect(constraints, const BoxConstraints(minWidth: 88.0, minHeight: 36.0));
     expect(padding, const EdgeInsets.symmetric(horizontal: 16.0));
     expect(shape, const RoundedRectangleBorder(
       borderRadius: BorderRadius.all(Radius.circular(2.0)),
     ));
-
+    expect(alignedDropdown, false);
+    expect(colorScheme, ThemeData.light().colorScheme);
     expect(tester.widget<Material>(find.byType(Material)).shape, shape);
     expect(tester.getSize(find.byType(Material)), const Size(88.0, 36.0));
   });
@@ -78,26 +86,33 @@ void main() {
   test('ButtonThemeData.copyWith', () {
     ButtonThemeData theme = const ButtonThemeData().copyWith();
     expect(theme.textTheme, ButtonTextTheme.normal);
+    expect(theme.layoutBehavior, ButtonBarLayoutBehavior.padded);
     expect(theme.constraints, const BoxConstraints(minWidth: 88.0, minHeight: 36.0));
     expect(theme.padding, const EdgeInsets.symmetric(horizontal: 16.0));
     expect(theme.shape, const RoundedRectangleBorder(
       borderRadius: BorderRadius.all(Radius.circular(2.0)),
     ));
     expect(theme.alignedDropdown, false);
+    expect(theme.colorScheme, null);
 
     theme = const ButtonThemeData().copyWith(
       textTheme: ButtonTextTheme.primary,
+      layoutBehavior: ButtonBarLayoutBehavior.constrained,
       minWidth: 100.0,
       height: 200.0,
       padding: EdgeInsets.zero,
       shape: const StadiumBorder(),
       alignedDropdown: true,
+      colorScheme: const ColorScheme.dark(),
+      materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
     );
     expect(theme.textTheme, ButtonTextTheme.primary);
+    expect(theme.layoutBehavior, ButtonBarLayoutBehavior.constrained);
     expect(theme.constraints, const BoxConstraints(minWidth: 100.0, minHeight: 200.0));
     expect(theme.padding, EdgeInsets.zero);
     expect(theme.shape, const StadiumBorder());
     expect(theme.alignedDropdown, true);
+    expect(theme.colorScheme, const ColorScheme.dark());
   });
 
   testWidgets('Theme buttonTheme defaults', (WidgetTester tester) async {