如何使墨迹效果填充BottomNavigationBarItem中的所有空间

dependencies:
  flutter:
    sdk: flutter
  flutter_material_color_picker: ^1.0.0

class MyBottomNavigationBar extends StatefulWidget {
  @override
  _MyBottomNavigationBarState createState() => _MyBottomNavigationBarState();
}

class _MyBottomNavigationBarState extends State<MyBottomNavigationBar> {
  int _currentIndex = 0;

  @override
  Widget build(BuildContext context) {
    return BottomNavigationBar(
      currentIndex: _currentIndex,
      onTap: (index) {
        setState(() {
          _currentIndex = index;
        });
      },
      items: [
        BottomNavigationBarItem(
          icon: Icon(Icons.home),
          label: 'Home',
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.search),
          label: 'Search',
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.person),
          label: 'Profile',
        ),
      ],
    );
  }
}

class _MyBottomNavigationBarState extends State<MyBottomNavigationBar> {
  int _currentIndex = 0;

  @override
  Widget build(BuildContext context) {
    return BottomNavigationBar(
      currentIndex: _currentIndex,
      onTap: (index) {
        setState(() {
          _currentIndex = index;
        });
      },
      items: [
        _buildBottomNavigationBarItem(
          icon: Icons.home,
          label: 'Home',
          index: 0,
        ),
        _buildBottomNavigationBarItem(
          icon: Icons.search,
          label: 'Search',
          index: 1,
        ),
        _buildBottomNavigationBarItem(
          icon: Icons.person,
          label: 'Profile',
          index: 2,
        ),
      ],
    );
  }

  BottomNavigationBarItem _buildBottomNavigationBarItem({
    IconData icon,
    String label,
    int index,
  }) {
    return BottomNavigationBarItem(
      icon: InkWell(
        onTap: () {
          setState(() {
            _currentIndex = index;
          });
        },
        child: Ink(
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(20),
            color: _currentIndex == index ? Colors.blue : Colors.transparent,
          ),
          child: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Icon(
              icon,
              color: _currentIndex == index ? Colors.white : Colors.black,
            ),
          ),
        ),
      ),
      label: label,
    );
  }
}