我也在这个问题上绊脚石，最终FutureBuilder为此使用了一个。看看我的路线：

final routes = {
  '/': (BuildContext context) => FutureBuilder<AuthState>(
    // This is my async call to sharedPrefs
    future: AuthProvider.of(context).authState$.skipWhile((_) => _ == null).first,
    builder: (BuildContext context, AsyncSnapshot<AuthState> snapshot) {
      switch(snapshot.connectionState) {
        case ConnectionState.done:
          // When the future is done I show either the LoginScreen 
          // or the requested Screen depending on AuthState
          return snapshot.data == AuthState.SIGNED_IN ? JobsScreen() : LoginScreen()
        default:
          // I return an empty Container as long as the Future is not resolved
          return Container();
      }
    },
  ),
};

如果要跨多个路径重用代码，则可以扩展FutureBuilder。