Flutter MultiProvider Classes构造函数问题 [英] Flutter MultiProvider Classes constructors issue

问题描述

我正在使用flutter创建购物应用程序，并使用Provider程序包进行状态管理.一切都很好，只是一个问题.我正在这样声明我的ChangeNotifierProviders.

I am creating a shopping app using flutter and using the Provider package for state management. Everything is working super fine just an issue. I am declaring my ChangeNotifierProviders like this.

void main() {
  runApp(MultiProvider(
    providers: <SingleChildWidget>[
      ChangeNotifierProvider(create: (_) => AuthStateManager.instance()),
      ChangeNotifierProvider(create: (_) => CartManager()),
      ChangeNotifierProvider(create: (_) => LocationManager()),
      ChangeNotifierProvider(create: (_) => BottomNavigationManager()),
      ChangeNotifierProvider(create: (_) => NotificationManager()),
    ],
    child: EvendorApp(),
  ));
}

所有课程都一样.

class NotificationManager with ChangeNotifier {
  NotificationManager() {
    print("Notification manager created");
  }
}

现在这些在状态管理方面运行良好，但是我想在其构造上执行一些代码，例如我想在其构造函数中运行代码，但是 AuthStateManager.instance()， BottomNavigationManager()和 CartManager()会在启动时执行代码，但在其余部分执行其他的 LocationManager()和 NotificationManager()不在执行代码，我不知道为什么会这样.我对所有班级都做同样的事情.

Now these are working fine in terms of state management, but I want to execute some code on their construction e.g. I wanna run code in their constructors, but AuthStateManager.instance() , BottomNavigationManager() and CartManager() are executing codes on start but rest of others LocationManager() and NotificationManager() are not executing code, I don't know why is this happening. I am doing the same for all classes.

推荐答案

我不确定这是否是答案，因为我从未使用过它，但是Provider软件包文档中确实说明了以下内容:

I am not sure if this is the answer as I never used it, but the Provider package documentation does states the following:

在使用提供程序的create/update回调时，值得注意的是，默认情况下此回调被延迟调用.这意味着，直到至少一次请求该值，才不会调用create/update回调.

When using the create/update callback of a provider, it is worth noting that this callback is called lazily by default. What this means is, until the value is requested at least once, the create/update callbacks won't be called.

如果是这种情况，那么解决方法是添加带有false值的lazy参数.像这样:

If it's the case here, then the solution would be to add the lazy parameter with a value of false. Something like so:

ChangeNotifierProvider(创建:(_)=> NotificationManager()，懒惰:false)

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