如何在 runApp(MyApp()); 之前使用环境变量

Question

我需要传递一个环境变量才能像这样使用

import 'package:flutter/foundation.dart' show kIsWeb;  
.
.
.
void main() {
  // check if is running on Web
  if (kIsWeb) {
  final appId = String.fromEnvironment('FACEBOOK_APP_ID',
  defaultValue: 'somedefaultvalue');
    // initialiaze the facebook javascript SDK
    FacebookAuth.instance.webInitialize(
      appId: appId,//<-- YOUR APP_ID
      cookie: true,
      xfbml: true,
      version: "v9.0",
    );
  }
  runApp(MyApp());
}

我收到一个错误

string.fromenvironment can only be used as a constant constructor

有办法吗？

谢谢

Answer 1

你会从 'final' 改为 'const 吗？

import 'package:flutter/foundation.dart' show kIsWeb;  
.
.
.
void main() {
  // check if is running on Web
  if (kIsWeb) {
  const appId = String.fromEnvironment('FACEBOOK_APP_ID',
  defaultValue: 'somedefaultvalue');
    // initialiaze the facebook javascript SDK
    FacebookAuth.instance.webInitialize(
      appId: appId,//<-- YOUR APP_ID
      cookie: true,
      xfbml: true,
      version: "v9.0",
    );
  }
  runApp(MyApp());
}

如何在 runApp(MyApp()); 之前使用环境变量

How to use env variable before runApp(MyApp());

environment-variables

facebook-authentication

flutter