Active color opacity level & gradient option

lib/bottom_navy_bar.dart

@@ -9,7 +9,6 @@ import 'package:flutter/widgets.dart';
 /// Update [selectedIndex] to change the selected item.
 /// [selectedIndex] is required and must not be null.
 class BottomNavyBar extends StatelessWidget {
-
   BottomNavyBar({
     Key? key,
     this.selectedIndex = 0,
@@ -23,8 +22,8 @@ class BottomNavyBar extends StatelessWidget {
     required this.items,
     required this.onItemSelected,
     this.curve = Curves.linear,
-  }) : assert(items.length >= 2 && items.length <= 5),
-       super(key: key);
+  })  : assert(items.length >= 2 && items.length <= 5),
+        super(key: key);
 
   /// The selected item is index. Changing this property will change and animate
   /// the item being selected. Defaults to zero.
@@ -125,10 +124,17 @@ class _ItemWidget extends StatelessWidget {
     required this.itemCornerRadius,
     required this.iconSize,
     this.curve = Curves.linear,
-  })  : super(key: key);
+  }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
+
+    List<double>? stops;
+    if (item.activeBackgroundColorGradient != null) {
+      int gradientLength = item.activeBackgroundColorGradient!.length;
+      stops = List<double>.generate(gradientLength, (index) => index / (gradientLength - 1));
+    }
+
     return Semantics(
       container: true,
       selected: isSelected,
@@ -138,8 +144,17 @@ class _ItemWidget extends StatelessWidget {
         duration: animationDuration,
         curve: curve,
         decoration: BoxDecoration(
-          color:
-              isSelected ? item.activeColor.withOpacity(0.2) : backgroundColor,
+          gradient: isSelected && item.activeBackgroundColorGradient != null && item.activeBackgroundColorGradient!.length > 0
+              ? LinearGradient(
+                  colors: item.activeBackgroundColorGradient!,
+                  stops: stops,
+                  begin: Alignment.topCenter,
+                  end: Alignment.bottomCenter,
+                )
+              : null,
+          color: isSelected
+              ? item.activeColor?.withOpacity(item.activeColorOpacityLevel)
+              : backgroundColor,
           borderRadius: BorderRadius.circular(itemCornerRadius),
         ),
         child: SingleChildScrollView(
@@ -157,7 +172,7 @@ class _ItemWidget extends StatelessWidget {
                   data: IconThemeData(
                     size: iconSize,
                     color: isSelected
-                        ? item.activeColor.withOpacity(1)
+                        ? item.activeColor?.withOpacity(1)
                         : item.inactiveColor == null
                             ? item.activeColor
                             : item.inactiveColor,
@@ -190,14 +205,15 @@ class _ItemWidget extends StatelessWidget {
 
 /// The [BottomNavyBar.items] definition.
 class BottomNavyBarItem {
-
   BottomNavyBarItem({
     required this.icon,
     required this.title,
-    this.activeColor = Colors.blue,
+    this.activeColor,
     this.textAlign,
     this.inactiveColor,
-  });
+    this.activeColorOpacityLevel = 0.2,
+    this.activeBackgroundColorGradient,
+  })   : assert(activeColor == null || activeBackgroundColorGradient == null);
 
   /// Defines this item's icon which is placed in the right side of the [title].
   final Widget icon;
@@ -207,14 +223,19 @@ class BottomNavyBarItem {
 
   /// The [icon] and [title] color defined when this item is selected. Defaults
   /// to [Colors.blue].
-  final Color activeColor;
+  final Color? activeColor;
 
   /// The [icon] and [title] color defined when this item is not selected.
   final Color? inactiveColor;
 
+  /// Used to configure active background opacity, if not set, it defaults to 0.2.
+  final double activeColorOpacityLevel;
+
+  /// Color gradient for background
+  final List<Color>? activeBackgroundColorGradient;
+
   /// The alignment for the [title].
   ///
   /// This will take effect only if [title] it a [Text] widget.
   final TextAlign? textAlign;
-
 }

test/bottom_navy_bar_test.dart

@@ -134,4 +134,33 @@ void main() {
     expect((containerFinder.decoration as BoxDecoration).boxShadow!.length, 1);
     expect((containerFinder.decoration as BoxDecoration).boxShadow!.first.blurRadius, 2);
   });
+
+  testWidgets('throws assertion error if both activeColor and activeBackgroundColorGradient are set', (WidgetTester tester) async {
+    expect(() async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            floatingActionButton: BottomNavyBar(
+              onItemSelected: onItemSelected,
+              items: <BottomNavyBarItem>[
+                BottomNavyBarItem(
+                  icon: Icon(Icons.apps),
+                  title: Text('Item 1'),
+                  activeBackgroundColorGradient: [Colors.pink, Colors.deepPurple, Colors.blue.shade900],
+                  activeColor: Colors.yellow,
+                  textAlign: TextAlign.center,
+                ),
+                BottomNavyBarItem(
+                  icon: Icon(Icons.people),
+                  title: Text('Item 2'),
+                  activeBackgroundColorGradient: [Colors.red, Colors.orange, Colors.yellow, Colors.green, Colors.blue, Colors.purple],
+                  textAlign: TextAlign.center,
+                ),
+              ],
+            ),
+          ),
+        ),
+      );
+    }, throwsAssertionError);
+  });
 }