颤动：打开更改的深色主题和浅色主题

Question

我想在boolean改变时改变主题，我已经改变了boolean的值但是为什么主题没有改变

Before Switched

After Switched

输出打印

false
true
true
false
false
true

布尔值已经改变，但主题没有改变

这是我的语法，有什么解决方案或替代方案吗？

ma​​in.dart

import 'global.dart' as global;

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      ....
      theme: global.modetheme
          ? ThemeData(primaryColor: Colors.white)
          : ThemeData.dark(),
      ....
    );
  }
}

global.dart

library myproject.global;

bool modetheme = false;

drawer.dart

import 'global.dart' as global;

SwitchListTile(
  value: global.modetheme,
    onChanged: (bool value) {
      setState(() {
        global.modetheme = value;
        print(global.modetheme);
         });
       },
     )