Flutter & Stream：getter 'name' 在 null 上被调用

Question

我正在尝试从firebase获取数据。但我遇到了一个错误。请注意，尽管有一个错误，但我仍然得到了数据。为什么在我获取数据之前/之前出现错误？为什么？我该如何修复它？

主要代码：

final loginUser = Provider.of<AllUser>(context);
print('user data : ${loginUser.name}');

功能：

Stream<AllUser> get loginUserData {
DocumentReference reference = userCollection.document(uid);
final Stream<DocumentSnapshot> snapshots = reference.snapshots();
return snapshots.map(
(snapshot) => AllUser(
name: snapshot.data['name'] ?? '',
email: snapshot.data['email'] ?? '',
uid: snapshot.data['uid'] ?? '',
signInMethod: snapshot.data['signInMethod'] ?? '',
locale: snapshot.data['locale'] ?? '',
score: '2000'),
);
}

错误消息：

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building ProfileSetting(dirty, dependencies: [_InheritedProviderScope<SystemUser>, _InheritedProviderScope<AllUser>, MediaQuery], state: _ProfileSettingState#48449):
The getter 'name' was called on null.
Receiver: null
Tried calling: name
The relevant error-causing widget was
ProfileSetting 
lib/…/profile_setting/profile_wrapper.dart:19
When the exception was thrown, this was the stack
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:51:5)
#1      _ProfileSettingState.build 
package:PhotoEarn/…/profile_setting/profile_setting.dart:38
#2      StatefulElement.build 
package:flutter/…/widgets/framework.dart:4758
#3      ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4641
#4      StatefulElement.performRebuild 
package:flutter/…/widgets/framework.dart:4813
...
════════════════════════════════════════════════════════════════════════════════
I/flutter (19228): user data : King of Light

我期待着你的来信。非常感谢。

Answer 1

@Uni在评论中建议作为社区wiki发布。

您的模型没有使用Streams，所以您所要做的就是将loginUserData函数更改为以下格式：

AllUser get loginUserData {
...
}

---

编辑：

发布整个代码，而且由于查询中只有1个文档，因此不需要迭代文档数组，因此代码可能看起来像：

Future<AllUser> get loginUserData async{
DocumentReference reference = userCollection.document(uid);
var document = await reference.get();
return new allUser(
name: document.data['name'] ?? '',
email: document.data['email'] ?? '',
uid: document.data['uid'] ?? '',
signInMethod: document.data['signInMethod'] ?? '',
locale: document.data['locale'] ?? '',
score: '2000');
}