如何将授权令牌从存储传递到 flutter 中的 header

Question

嘿伙计们，我有这个问题，使用flutter_secure_storage从flutter中的存储中获取的令牌传递给header，但它不起作用，如果我将令牌分配给Z46F3EA056CAA3126B91F3F70BEEA0中的不同密钥，则它会抛出错误6B91F3F70BEEA0 Null 不是 'Map<dynamic, dynamic>' 类型的子类型

我用于存储和检索令牌的代码

 Future setToken(String token)async{
   await _storage.write(key: 'Bearer', value: token);
}
  Future<String?>get_bearer_key() async{
     String? token = await _storage.read(key: 'Bearer');
     return token;
  }

我将令牌传递给 header 的代码

 String? key = await get_bearer_key();

      try{

        Map<String,String> requestHeader = new Map();
        requestHeader['Content-type'] = 'application/json';
        requestHeader['Accept'] = 'application/json';
        requestHeader['Authorization'] = '$key';
        requestHeader['Request-Channel'] = 'mobile';

      if(activation_code == null){
        return setState(() {
          error = "missing credentials";
        });
      }

      var url = Uri.parse('$baseUrl/users/activate-account');
      final body = jsonEncode({
        "activation_code": activation_code,
      });

     Response reponse = await put(url,body:body,
          headers: requestHeader
      );

      Map data = jsonDecode(reponse.body);
      print(data);