test.dart

class AppConfig{
  bool is_login ;
  String username;
  AppConfig({this.is_login, this.username});
}
class MyApp{
  static AppConfig appconfig = new AppConfig(is_login: false, username: "guest");
  static updateConfig(AppConfig aconfig){
    appconfig = aconfig;
  }
}

void main(){
  AppConfig bconfig = new AppConfig(username: "张晓亚",is_login: true);
  MyApp.updateConfig(bconfig);
  print(MyApp.appconfig.is_login);
  print(MyApp.appconfig.username);
  print(true);
}