Flutter：如何在CupertinoTabBar中显示徽章并根据用户输入更新值

Question

我有一个带有CupertinoTabScaffold，CupertinoTabBar和一系列BottomNavigationBarItem的CupertinoApp。我设法在BottomNavigationBarItem（购物篮标签）之一中添加了徽章。看到下面的图片以及我的代码

import numpy as np

def microcar(expected, actual):
    horizontal_expected = expected[0,1]*expected[0,2]*np.cos(expected[0,0])
    vertical_expected = expected[0,1]*expected[0,2]*np.sin(expected[0,0])

    horizontal_actual = actual[0,1]*actual[0,2]*np.cos(actual[0,0])
    vertical_actual = actual[0,1]*actual[0,2]*np.sin(actual[0,0])

    distance_expected = expected[0,1]*expected[0,2]
    distance_actual = actual[0,1]*actual[0,2]


    return horizontal_expected, vertical_expected, horizontal_actual, vertical_actual, distance_expected, distance_actual

现在，我想基于在另一个标签之一中触发的事件来更新徽章文本。我将徽章的值存储为单例（class _HomeScreenState extends State<HomeScreen> { @override Widget build(BuildContext context) { return CupertinoTabScaffold( tabBar: CupertinoTabBar( backgroundColor: kColorPrimaryLight, items: [ BottomNavigationBarItem( icon: Icon(CupertinoIcons.search), title: Text('Discover'), ), BottomNavigationBarItem( icon: Icon(CupertinoIcons.person_solid), title: Text('Account'), ), BottomNavigationBarItem( icon: Icon(CupertinoIcons.book_solid), title: Text('Stories'), ), BottomNavigationBarItem( icon: Badge( badgeContent: Text( appData.basketList.length.toString(), style: kDescriptionTextStyle, ), child: Icon(CupertinoIcons.shopping_cart)), title: Text('Basket'), ), ], ), ），此信息可用于所有屏幕。每次触发该事件时，appData.basketList.length.toString（）都会更改，但我的徽章不会更改。仅当我热装时它才会改变...所以这是我的问题：如何更新徽章的文字？

谢谢！