发生 Flutter 运行时异常。 _TypeError（类型 'List<dynamic>' 不是类型 'String' 的子类型）

Question

当我尝试从 Firestore 获取数据时，会发生此异常。 _TypeError（类型“列表”不是“字符串”类型的子类型） 我找不到问题的原因。请帮忙。

class ActfMiddleWare {
      ///Fetches LocationData From Firestore and Save it in Store;
      locationIndexMiddleware() {
        return (Store<AppState> store, action, NextDispatcher next) async {
          if (action is GetLocationIndex) {
            Future<DocumentSnapshot<Map<String, dynamic>>> locationIndex =
                FirebaseFirestore.instance
                    .collection('locations')
                    .doc('locationIndex')
                    .get();
    
            await locationIndex.then((docSnapshot) {
              if (docSnapshot.data() != null) {
                List temp = docSnapshot.data()!['locations'];
    
                store.dispatch(SaveLocationIndex(payload: temp));
              }
            });
          }
          next(action);
        };
      }
    }

Answer 1

错误是您在列表中转换字符串数据。

检查数据库中的数据。

这是您需要将列表更改为字符串的修复方法。

String temp = docSnapshot.data()!['locations'];

这是完整的代码

class ActfMiddleWare {
      ///Fetches LocationData From Firestore and Save it in Store;
      locationIndexMiddleware() {
        return (Store<AppState> store, action, NextDispatcher next) async {
          if (action is GetLocationIndex) {
            Future<DocumentSnapshot<Map<String, dynamic>>> locationIndex =
                FirebaseFirestore.instance
                    .collection('locations')
                    .doc('locationIndex')
                    .get();
    
            await locationIndex.then((docSnapshot) {
              if (docSnapshot.data() != null) {
                String temp = docSnapshot.data()!['locations']; -->Here is the change
    
                store.dispatch(SaveLocationIndex(payload: temp));
              }
            });
          }
          next(action);
        };
      }
    }