Question

我正在尝试从 firestore 显示用户的爱好列表，我从那里获取值，因为它在控制台中打印但无法显示。

错误：-

    The getter 'hobbies' was called on null.
    Receiver: null
    Tried calling: hobbies

创建账户数据是模型类：-

   Future<CreateAccountData> getUser() async {
   final User user = auth.currentUser;
  return _reference.doc(user.uid).get().then((m) =>   CreateAccountData.fromDocument(m));
    }

以这种方式获取数据并在控制台中打印出来：-

 List hobbies;

 void initState() {
 super.initState();
 getUser().then((value) {
  if (!mounted) return;
  setState(() {
    
      accountData = value;
      
      hobbies = value.hobbies;
      print("hobbies"+ hobbies.toString());


  });
});
}

错误将我带到我评论的那一行：-

           child:GridView.builder(
                   physics: BouncingScrollPhysics(),
                   scrollDirection: Axis.horizontal,
                   shrinkWrap: true,
                   itemCount: accountData.hobbies.length, // Error take me to hobbies.
                        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2, childAspectRatio: 5, crossAxisSpacing: 5,),
                        itemBuilder: (BuildContext context, int index){
                          
                          return Padding(
                            padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
                            child: Text(accountData.hobbies[index]),
                          );
                        }
                    ),

关于更新到此的建议（包含在未来的构建器中）：-

         child: FutureBuilder(
                      future: getUser(),
                      builder: (context, snapshot){
                        if(snapshot.connectionState == ConnectionState.waiting){
                          return Center(
                            child: CircularProgressIndicator(),
                          );
                        } if(snapshot.data.docs.isEmpty){
                          return Align(
                            alignment: FractionalOffset.centerLeft,
                            child: Text("Add what you love to do.....",textAlign: TextAlign.left,style: TextStyle(fontSize: 17),),
                          );
                        }
                          return GridView.builder(
                              physics: BouncingScrollPhysics(),
                              scrollDirection: Axis.horizontal,
                              shrinkWrap: true,
                              itemCount: accountData?.hobbies?.length ?? 0,
                              gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                                crossAxisCount: 2,
                                childAspectRatio: 5,
                                crossAxisSpacing: 5,),
                              itemBuilder: (BuildContext context,
                                  int index) {
                                 return Padding(
                                  padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
                                  child: Text(accountData.hobbies[index]),
                                );
                              }
                          );
                        },
                    ),

现在收到 NoSuchMethodError 错误：-

      Class 'CreateAccountData' has no instance getter 'docs'.
      Receiver: Instance of 'CreateAccountData'
      Tried calling: docs

Answer 1

如果您已创建变量并为其赋值，但它仍然显示 getter 'value' was called on null，尝试Run 或Restart 您的应用而不是Hot Reload。因为 Hot Reload 不会调用 initstate()（变量分配它们的值），它只会被 Restarting 应用调用。

Answer 2

检查爱好为空

chmod

Answer 3

在 flutter 2.0 中，我们有空安全。我们需要检查值是否为空或不使用 !在变量后标记。我会在几分钟内发布代码，因为我在学校rn

Answer 4

将 mi.HTMLBody 包裹在 GridView.builder 中，将 FutureBuilder 作为 getUser() 传递。

future

getter 被调用为 null

4 个答案: