减少底部导航栏中的顶部和底部填充

Question

我想减少BottomNavigationBar的顶部和底部填充，但我想保持相同的图标高度和条形图高度为50像素：

bottomNavigationBar: SizedBox(
height: 50,
child: BottomNavigationBar(
showSelectedLabels: false,
showUnselectedLabels: false,
type: BottomNavigationBarType.fixed,
elevation: 5.0,
currentIndex: 0,
items: buildBottomBarItems(),
),
)

构建底部条形项目的方法：

List<BottomNavigationBarItem> buildBottomBarItems() {
List<BottomNavigationBarItem> _bottomBarItems = List();
List<String> _iconNames = ["home", "search", "plus", "heart"];
for (var i = 0; i < _iconNames.length; ++i) {
_bottomBarItems.add(
BottomNavigationBarItem(
icon: Container(
child: new Image.asset('assets/' + _iconNames[i] + '.png', width: 24, height: 24)
),
title: Text('')
)
);
}
}

(在当前情况下，存在4.0像素的溢出(。谢谢