错误状态：更新 firebase 包后 DocumentSnapshotPlatform 中不存在字段

Question

我更新了以下软件包：

• firebase_core：从 ^0.5.0+1 到 ^1.2.0
• cloud_firestore：从 0.14.1+3 到 ^2.2.0
• firebase_auth：从 ^0.18.0+1 到 ^1.2.0

更新软件包后，我收到以下错误：

═══════ Exception caught by widgets library ═══════════════════════════════════
The following StateError was thrown building StreamBuilder<QuerySnapshot<Object?>>(dirty, state: _StreamBuilderBaseState<QuerySnapshot<Object?>, AsyncSnapshot<QuerySnapshot<Object?>>>#77e63):
Bad state: field does not exist within the DocumentSnapshotPlatform

The relevant error-causing widget was
StreamBuilder<QuerySnapshot<Object?>>
lib/screens/app_home.dart:183
When the exception was thrown, this was the stack
#0      DocumentSnapshotPlatform.get._findKeyValueInMap
package:cloud_firestore_platform_interface/…/platform_interface/platform_interface_document_snapshot.dart:86
#1      DocumentSnapshotPlatform.get._findComponent
package:cloud_firestore_platform_interface/…/platform_interface/platform_interface_document_snapshot.dart:104
#2      DocumentSnapshotPlatform.get
package:cloud_firestore_platform_interface/…/platform_interface/platform_interface_document_snapshot.dart:120
#3      _JsonDocumentSnapshot.get
package:cloud_firestore/src/document_snapshot.dart:92
#4      _JsonDocumentSnapshot.[]
package:cloud_firestore/src/document_snapshot.dart:96
...
════════════════════════════════════════════════════════════════════════════════

下面是flutter doctor的输出：

flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.3, on macOS 11.3.1 20E241 darwin-x64, locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.56.2)
[✓] Connected device (3 available)

• No issues found!

以下是与错误相关的代码：

final coursesCollection = FirebaseFirestore.instance.collection('courses').limit(10).where('courseLive', isEqualTo: true);
.
.
.
    return StreamBuilder<QuerySnapshot>(
      stream: coursesCollection.snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return Center(
            child: CircularProgressIndicator(
              backgroundColor: kAccentColor,
            ),
          );
        }
        final courseSnapshot = snapshot.data.docs;
        List<CourseTile> courseTiles = [];
        CourseData course;
        for (var courseData in courseSnapshot) {
          course = CourseData.fromDocumentSnapshot(snapshot: courseData);
          final courseDocID = course.courseDocID; 
          final courseID = course.courseID; 
          final courseTitle = course.courseTitle; 
          final courseDescription = course.courseDescription; 
          final courseSubTitle = course.courseSubTitle; 
          final courseBadge = course.courseBadge; 
          final courseLevel = course.courseLevel; 
          final coursePaid = course.coursePaid; 
          final courseImage = course.courseImage;
          final courseBgColor = hexToColor(course.courseBackgroundColor); 
          final courseBgColor1 = hexToColor(course.courseBgColor1); 
          final courseBgColor2 = hexToColor(course.courseBgColor2); 
          final courseFgColor = hexToColor(course.courseFgColor); 
          final courseDeliveryFormat = course.courseDeliveryFormat;
          final courseLive = course.courseLive;

          final courseTile = CourseTile(
            cardBackgroundColor: courseBgColor,
            bgColor1: courseBgColor1,
            bgColor2: courseBgColor2,
            fgColor: courseFgColor,
            cardImage: courseImage,
            titleText: courseTitle,
            titleTextColor: courseFgColor,
            subTitleText: courseSubTitle,
            courseID: courseID,
            courseDocID: courseDocID,
          );

          courseTiles.add(courseTile);
         }
         return Expanded(
          child: ListView(
            children: courseTiles,
          ),
        );
      },
    );

我确实验证了 Firestore 文档中存在的字段，它们确实匹配。还尝试将包恢复到以前的版本，但它仍然中断。

不确定，需要采取什么措施来解决此问题。

任何帮助将不胜感激。

非常感谢您提前抽出时间。

应用维克多建议的解决方案后

Bad state: field does not exist 错误已消失。但是，我仍然收到以下错误。

════════ Exception caught by widgets library ═══════════════════════════════════
The following _TypeError was thrown building StreamBuilder<QuerySnapshot<Object?>>(dirty, state: _StreamBuilderBaseState<QuerySnapshot<Object?>, AsyncSnapshot<QuerySnapshot<Object?>>>#ef5a5):
type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'DocumentSnapshot<Object>'

The relevant error-causing widget was
StreamBuilder<QuerySnapshot<Object?>>
lib/screens/app_home.dart:183
When the exception was thrown, this was the stack
#0      CourseStream.build.<anonymous closure>
lib/screens/app_home.dart:200
#1      StreamBuilder.build
package:flutter/…/widgets/async.dart:545
#2      _StreamBuilderBaseState.build
package:flutter/…/widgets/async.dart:124
#3      StatefulElement.build
package:flutter/…/widgets/framework.dart:4612
#4      ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4495
...
════════════════════════════════════════════════════════════════════════════════

下面是CourseData 类中的方法，它解析从文档快照接收到的数据。

CourseData.fromDocumentSnapshot({DocumentSnapshot snapshot}) {
    courseDocID = snapshot.id;
    courseID = snapshot['courseID'];
    courseTitle = snapshot['courseTitle'];
    courseSubTitle = snapshot['courseSubTitle'];
    courseDescription = snapshot['courseDescription'];
    courseLevel = snapshot['courseLevel'];
    courseBadge = snapshot['courseType'];
    coursePaid = snapshot['coursePaid'];
    courseCategories = snapshot['courseCategories'];
    courseImage = snapshot['courseImage'];
    courseBackgroundColor = snapshot['courseBackgroundColor'];
    courseForegroundColor = snapshot['courseForegroundColor'];
    courseBgColor1 = snapshot['courseBgColor1'];
    courseBgColor2 = snapshot['courseBgColor2'];
    courseFgColor = snapshot['courseFgColor'];
    courseDeliveryFormat = snapshot['courseDeliveryFormat'];
    courseLive = snapshot['courseLive'];
  }

Answer 1

为了从您的DocumentSnapshot 获取数据，您需要在快照上调用.data()。

DocumentSnapshotPlatform

包含从一个 Firestore 数据库中的文档。

可以通过调用data()或者调用get()来获取数据 一个特定的字段。

DocumentSnapshotPlatform class

解决方案：

您可以保持原样：

    course = CourseData.fromDocumentSnapshot(snapshot: courseData);

并将 CourseData 代码更新为以下代码块：

    CourseData.fromDocumentSnapshot({DocumentSnapshot snapshot}) {
    Map<String, dynamic> snapshotData = snapshot.data();
    courseDocID = snapshot.id;
    courseID = snapshotData['courseID'];
    courseTitle = snapshotData['courseTitle'];
    courseSubTitle = snapshotData['courseSubTitle'];
    courseDescription = snapshotData['courseDescription'];
    courseLevel = snapshotData['courseLevel'];
    courseBadge = snapshotData['courseType'];
    coursePaid = snapshotData['coursePaid'];
    courseCategories = snapshotData['courseCategories'];
    courseImage = snapshotData['courseImage'];
    courseBackgroundColor = snapshotData['courseBackgroundColor'];
    courseForegroundColor = snapshotData['courseForegroundColor'];
    courseBgColor1 = snapshotData['courseBgColor1'];
    courseBgColor2 = snapshotData['courseBgColor2'];
    courseFgColor = snapshotData['courseFgColor'];
    courseDeliveryFormat = snapshotData['courseDeliveryFormat'];
    courseLive = snapshotData['courseLive'];
  }