Dart：未为类型 'Object? Function()' 定义运算符“[]”。尝试定义运算符 '[]'

Question

我正在创建一个 Flutter 应用程序，但在实施 Firebase 时卡住了。

    enter  return Container(
        child: StreamBuilder<QuerySnapshot>(
            stream: quizStream.snapshots(),
            builder: (context, snapshot) {
              return snapshot.data != null
                  ? Container()
                  : ListView.builder(
                      itemCount: snapshot.data!.docs.length,
                      itemBuilder: (context, index) {
                        return QuizTile(
                          ImgUrl: snapshot.data!.docs[index].data()["imgdesc"] ,
                        );
                      });
            }));
  }

ImgUrl: snapshot.data!.docs[index].data()["imgdesc"]

这是我遇到错误的行，它告诉我：

the operator '[]' isn't defined for the type 'Object? Function()'. Try defining the operator '[]'.

Answer 1

您需要将其转换为 Map<String,dynamic>

ImgUrl: snapshot.data!.docs[index].data() as Map<String,dynamic>["imgdesc"],

或者使用这个：

ImgUrl: snapshot.data!.docs[index].get('imgdesc'),

Dart：未为类型 'Object? Function()' 定义运算符“[]”。尝试定义运算符 '[]'

Dart: The operator '[]' isn't defined for the type 'Object? Function()'. Try defining the operator '[]'

dart

flutter