我已经在我的应用程序中创建了一个底部导航菜单，我想创建一个动画圆形菜单时，我点击交易按钮。

当我单击"交易“时，我希望它像这样弹出

这是我当前的bottomNav代码

bottomNavigationBar: BottomNavigationBar(
    items: const <BottomNavigationBarItem>[
      BottomNavigationBarItem(
        icon: Icon(Icons.home),
        label: 'Home',
      ),
      BottomNavigationBarItem(
        icon: Icon(Icons.swap_horiz),
        label: 'Transact',
      ),
      BottomNavigationBarItem(
        icon: Icon(Icons.settings),
        label: 'Settings',
      ),
    ],
    currentIndex: _selectedIndex,
    selectedItemColor: MyColors.greenSuccess,
    onTap: _onItemTapped,
  ),

//function when item is tapped
void _onItemTapped(int index) {
setState(() {
  _selectedIndex = index;
});

//check which item is selected
if(index == 0){
  //go home
}
else if(index == 1){
  //open trans menu here

}
else{
  // go to settings

}
}