Added configurable border width and disable flag for the shadow on tapping (helpful if you want a flat button and the elevation is 0)

example/android/build.gradle

@@ -26,6 +26,6 @@ subprojects {
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }

lib/src/group_button_base.dart

@@ -123,8 +123,10 @@ class GroupButton<T> extends StatelessWidget {
       selectedBorderColor: options.selectedBorderColor,
       unselectedBorderColor: options.unselectedBorderColor,
       borderRadius: options.borderRadius,
+      borderWidth: options.borderWidth,
       selectedShadow: options.selectedShadow,
       unselectedShadow: options.unselectedShadow,
+      tappingShadowColor: options.tappingShadowColor,
       buttonWidth: options.buttonWidth,
       buttonHeight: options.buttonHeight,
       mainGroupAlignment: options.mainGroupAlignment,

lib/src/group_button_body.dart

@@ -27,8 +27,10 @@ class GroupButtonBody<T> extends StatefulWidget {
     this.selectedColor,
     this.unselectedColor,
     this.borderRadius = BorderRadius.zero,
+    this.borderWidth,
     this.selectedShadow = const [],
     this.unselectedShadow = const [],
+    this.tappingShadowColor,
     this.buttonWidth,
     this.buttonHeight,
     this.mainGroupAlignment = MainGroupAlignment.center,
@@ -59,8 +61,10 @@ class GroupButtonBody<T> extends StatefulWidget {
   final Color? selectedBorderColor;
   final Color? unselectedBorderColor;
   final BorderRadius? borderRadius;
+  final double? borderWidth;
   final List<BoxShadow> selectedShadow;
   final List<BoxShadow> unselectedShadow;
+  final Color? tappingShadowColor;
   final double? buttonWidth;
   final double? buttonHeight;
   final GroupingType? groupingType;
@@ -166,10 +170,8 @@ class _GroupButtonBodyState<T> extends State<GroupButtonBody<T>> {
         );
       } else {
         button = GroupButtonItem(
-          text: widget.buttonIndexedTextBuilder
-                  ?.call(_isSelected(i), i, context) ??
-              widget.buttonTextBuilder
-                  ?.call(_isSelected(i), widget.buttons[i], context) ??
+          text: widget.buttonIndexedTextBuilder?.call(_isSelected(i), i, context) ??
+              widget.buttonTextBuilder?.call(_isSelected(i), widget.buttons[i], context) ??
               widget.buttons[i].toString(),
           onPressed: _controller.disabledIndexes.contains(i)
               ? () => _controller.onDisablePressed?.call(i)
@@ -186,8 +188,10 @@ class _GroupButtonBodyState<T> extends State<GroupButtonBody<T>> {
           selectedBorderColor: widget.selectedBorderColor,
           unselectedBorderColor: widget.unselectedBorderColor,
           borderRadius: widget.borderRadius,
+          borderWidth: widget.borderWidth,
           selectedShadow: widget.selectedShadow,
           unselectedShadow: widget.unselectedShadow,
+          tappingShadowColor: widget.tappingShadowColor,
           height: widget.buttonHeight,
           width: widget.buttonWidth,
           textAlign: widget.textAlign,
@@ -199,9 +203,7 @@ class _GroupButtonBodyState<T> extends State<GroupButtonBody<T>> {
 
       /// Padding adding
       /// when groupingType is row or column
-      if (widget.spacing > 0.0 &&
-          widget.buttonIndexedBuilder == null &&
-          widget.buttonBuilder == null) {
+      if (widget.spacing > 0.0 && widget.buttonIndexedBuilder == null && widget.buttonBuilder == null) {
         if (widget.groupingType == GroupingType.row) {
           button = Padding(
             padding: EdgeInsets.symmetric(horizontal: widget.spacing),
@@ -230,18 +232,14 @@ class _GroupButtonBodyState<T> extends State<GroupButtonBody<T>> {
     } else {
       final maxSelected = widget.maxSelected;
       final selectedIndexesCount = _controller.selectedIndexes.length;
-      if (maxSelected != null &&
-          selectedIndexesCount >= maxSelected &&
-          !_controller.selectedIndexes.contains(i)) {
+      if (maxSelected != null && selectedIndexesCount >= maxSelected && !_controller.selectedIndexes.contains(i)) {
         return;
       }
       _controller.toggleIndexes([i]);
     }
   }
 
   bool _isSelected(int i) {
-    return widget.isRadio
-        ? _controller.selectedIndex == i
-        : _controller.selectedIndexes.contains(i);
+    return widget.isRadio ? _controller.selectedIndex == i : _controller.selectedIndexes.contains(i);
   }
 }

lib/src/group_button_item.dart

@@ -14,8 +14,10 @@ class GroupButtonItem extends StatelessWidget {
     this.selectedColor,
     this.unselectedColor,
     this.borderRadius,
+    this.borderWidth,
     this.selectedShadow,
     this.unselectedShadow,
+    this.tappingShadowColor,
     this.height,
     this.width,
     this.textAlign,
@@ -35,8 +37,10 @@ class GroupButtonItem extends StatelessWidget {
   final Color? selectedBorderColor;
   final Color? unselectedBorderColor;
   final BorderRadius? borderRadius;
+  final double? borderWidth;
   final List<BoxShadow>? selectedShadow;
   final List<BoxShadow>? unselectedShadow;
+  final Color? tappingShadowColor;
   final double? height;
   final double? width;
   final TextAlign? textAlign;
@@ -64,6 +68,8 @@ class GroupButtonItem extends StatelessWidget {
           ? unselectedBorderColor
           : null;
 
+  double get _borderWidth => borderWidth ?? 1.0;
+
   @override
   Widget build(BuildContext context) {
     return Container(
@@ -87,6 +93,7 @@ class GroupButtonItem extends StatelessWidget {
     return ElevatedButton(
       onPressed: onPressed,
       style: ElevatedButton.styleFrom(
+        shadowColor: tappingShadowColor ?? _getBackgroundColor(theme),
         elevation: elevation ?? 0.0,
         backgroundColor: _getBackgroundColor(theme),
         shape: _buildShape(),
@@ -136,7 +143,7 @@ class GroupButtonItem extends StatelessWidget {
 
   BorderSide buildBorderSide(Color? color) {
     if (color != null) {
-      return BorderSide(color: color);
+      return BorderSide(color: color, width: _borderWidth);
     }
     return BorderSide.none;
   }

lib/src/options/defaults.dart

@@ -24,3 +24,6 @@ const defaultUnselectedTextStyle = TextStyle(
   fontSize: 14,
   color: Colors.black,
 );
+
+@protected
+const defaultTappingShadowColor = Color.fromARGB(18, 18, 18, 20);

lib/src/options/group_button_options.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-
 import 'package:group_button/group_button.dart';
 import 'package:group_button/src/options/defaults.dart';
 
@@ -17,8 +16,10 @@ class GroupButtonOptions {
     this.selectedBorderColor,
     this.unselectedBorderColor,
     this.borderRadius,
+    this.borderWidth,
     this.selectedShadow = defaultShadow,
     this.unselectedShadow = defaultShadow,
+    this.tappingShadowColor = defaultTappingShadowColor,
     this.buttonHeight,
     this.buttonWidth,
     this.mainGroupAlignment = MainGroupAlignment.center,
@@ -74,12 +75,18 @@ class GroupButtonOptions {
   /// How much the button will be rounded
   final BorderRadius? borderRadius;
 
+  /// The width of the button's border
+  final double? borderWidth;
+
   /// list of selected button(s) [BoxShadow]
   final List<BoxShadow> selectedShadow;
 
   /// list of unselected buttons [BoxShadow]
   final List<BoxShadow> unselectedShadow;
 
+  /// shadow [Color] shown when performing an onTap()
+  final Color? tappingShadowColor;
+
   /// Height of Group button
   final double? buttonHeight;