Question

我正在使用提供程序包进行状态管理，我不知道此问题是否是由于提供程序造成的，还是我在这里丢失了一些东西，我感谢能发现我的错误的人，

这是我的ChangeNotifier类


class Db extends ChangeNotifier {

  bool _fetchingData = false;
  User _user;

  User get getCurrentUser{
    return _user;
  }

  set setUser(User user){
    print('db_class.dart 15: Setting the user');
    _user = user;
  }

  void setFetchingData(bool state){
    _fetchingData = state;
    notifyListeners();
  }

  bool get isFetching{
    return _fetchingData;
  }

}

请关注这个吸气剂

User get getCurrentUser{
    return _user;
  }

使用此类的createUser方法创建该用户后，我应该获得该用户的实例

class Auth extends Db {

  Future<IdTokenResult> signIn(String email, String password) {...}

  Future<IdTokenResult> signUp(String email, String password) {...}

  Future<void> signOut() {...}

  static bool isTokenExpired(DateTime dateTime) {{...}



  void createUser(IdTokenResult idToken) {
    print('auth.dart 53: creatUser method is called');
    User user;

    switch (idToken.claims['claim']) {
      case 'Admin':
        setUser = Admin(
            uid: idToken.claims['user_id'],
            email: idToken.claims['email'],
            token: idToken.claims['token'],
            claim: ClaimsType.Admin,
            phoneNumber: idToken.claims['phone_number']);
        break;
      case 'ShopOwner':
        setUser = ShopOwner(
            uid: idToken.claims['user_id'],
            email: idToken.claims['email'],
            token: idToken.claims['token'],
            claim: ClaimsType.ShopOwner,
            shopName: idToken.claims['name'],
            phoneNumber: idToken.claims['phone_number'],
            //ToDo: get first name and last
            firstName: 'amjed',
            lastName: 'al anqoodi',
            ownerPhotoUrl: idToken.claims['photoUrl']);

        break;
      default:
        setUser = Customer(
            uid: idToken.claims['user_id'],
            email: idToken.claims['email'],
            token: idToken.claims['token'],
            phoneNumber: idToken.claims['phone_number'],
            userDisplayName: 'test',
            userRealName: 'amjed san',
            userFamilyName: 'al anqoodi',
            country: 'oman',
            city: 'nizwa',
            village: 'marfa daris');
        break;
    }
    print('auth.dart 94: ${getCurrentUser.email}');
//    print('auth.dart 75: ${user.email}');

  }
}

问题是，当我在添加产品页面中调用getter getCurrentUser时，我得到一个空值，为什么？

class AddProductPage extends StatefulWidget {

  @override
  _AddProductPageState createState() => _AddProductPageState();
}

class _AddProductPageState extends State<AddProductPage> {

  List<Asset> images = List<Asset>();
  String _error;
  TextEditingController productNameController = TextEditingController();
  TextEditingController priceController = TextEditingController();

  @override
  void initState() {
    super.initState();
  }

  Widget buildGridView() {...}

  Future<void> loadAssets() async {...}



  @override
  Widget build(BuildContext context){
    var db = Provider.of<Db>(context);
    return Padding(
      padding: const EdgeInsets.all(15.0),
      child: Center(
        child: Column(
          children: <Widget>[
            Text('Shop Owner Page'),
            TextField(
              controller: productNameController,
              decoration: InputDecoration(
                  hintText: 'Product Name'
              ),
            ),
            TextField(
              controller: priceController,
              decoration: InputDecoration(
                  hintText: 'Product Price'
              ),
            ),
            Center(child: Text('Error: $_error')),
            RaisedButton(
              child: Text("Pick images"),
              onPressed: loadAssets,
            ),
            Expanded(
              child: buildGridView(),
            ),
            RaisedButton(
              child: Text('Add The Product'),
              onPressed: () async{
                if(db.getCurrentUser == null){
                  print('add_product 103: user is null');
                }else{
                  print('add_product 105: user is not null');
                }
                print('add_product 107: ${db.getCurrentUser.email}');
                print('add_product 108: ${(db.getCurrentUser as ShopOwner).shopName}');
//                ShopsManagement shopsManagement = ShopsManagement();
//                await shopsManagement.addProduct(claim: (auth.getCurrentUser as ShopOwner).claim, shopName: (auth.getCurrentUser as ShopOwner).shopName , productName: productNameController.text, price: double.parse(priceController.text), assets: images);
              },
            ),
          ],
        ),
      ),
    );
  }
}

问题就在这里，当我调用onPress方法时，我在“ db.getCurrentUser”上得到的是空值，

RaisedButton( child: Text('Add The Product'), onPressed: () async{ if(db.getCurrentUser == null){ print('add_product 103: user is null'); }else{ print('add_product 105: user is not null'); } print('add_product 107: ${db.getCurrentUser.email}'); print('add_product 108: ${(db.getCurrentUser as ShopOwner).shopName}'); // ShopsManagement shopsManagement = ShopsManagement(); // await shopsManagement.addProduct(claim: (auth.getCurrentUser as ShopOwner).claim, shopName: (auth.getCurrentUser as ShopOwner).shopName , productName: productNameController.text, price: double.parse(priceController.text), assets: images); }, ),

Answer 1

我认为您必须在_user = user;方法的这一行setUser之后调用notifyListeners。

为什么我会得到一个空值？

1 个答案: