Flutter 云Firestore StreamBuilder<documentsnapshot> 错误</documentsnapshot>

Question

更新我的 flutter 插件后，我不得不更新我的代码，因为我收到类似“Firestore”已弃用且不应使用的错误。 Class Firestore 已弃用，请改用“FirebaseFirestore”。

我按照警告更新了我的代码，但现在我的 streamBuilders 不工作我不知道为什么。

这是我的代码

class PickupLayout extends StatelessWidget {


final Widget scaffold;
  final CallMethods callMethods = CallMethods();

  PickupLayout({
    @required this.scaffold,
  });

  @override
  Widget build(BuildContext context) {
    final UserProvider userProvider = Provider.of<UserProvider>(context);

return (userProvider != null && userProvider.getUser != null)
    ? StreamBuilder<DocumentSnapshot>(
        stream: callMethods.callStream(uid: userProvider.getUser.uid),
        builder: (context, snapshot) {
          if (snapshot.hasData && snapshot.data.data != null) {
            Call call = Call.fromMap(snapshot.data.data());

            if (!call.hasDialled) {
              return PickupScreen(call: call);
            }
          }
          return scaffold;
        },
      )
    : Scaffold(
        body: Center(
          child: CircularProgressIndicator(),
        ),
      );
  }
}

这是错误

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building StreamBuilder<DocumentSnapshot>(dirty, state: _StreamBuilderBaseState<DocumentSnapshot, AsyncSnapshot<DocumentSnapshot>>#a2802):
The method '[]' was called on null.
Receiver: null
Tried calling: []("caller_id")
The relevant error-causing widget was
StreamBuilder<DocumentSnapshot>
package:vdb_tinus_app/…/pickup/pickup_layout.dart:22
When the exception was thrown, this was the stack
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1      new Call.fromMap
package:vdb_tinus_app/…/models/call.dart:37
#2      PickupLayout.build.<anonymous closure>
package:vdb_tinus_app/…/pickup/pickup_layout.dart:26
#3      StreamBuilder.build
package:flutter/…/widgets/async.dart:525
#4      _StreamBuilderBaseState.build

在更新我的云if (snapshot.hasData && snapshot.data.data.= null) { Call call = Call.fromMap(snapshot.data;data);插入之前，根据日志显示错误的行过去看起来像这样if (snapshot.hasData && snapshot.data.data.= null) { Call call = Call.fromMap(snapshot.data;data); 更新后我不得不将其更改为此if (snapshot.hasData && snapshot.data.data.= null) { Call call = Call.fromMap(snapshot.data;data());

Answer 1

在这一行中， if (snapshot.hasData && snapshot.data.data != null) { ，您正在检查DocumentSnapshot.data是否为 null。因为它是 function（因此，一个对象），您的比较永远不会评估为false 。

在下一行snapshot.data.data()中，您正在调用上面的 function，其返回值很可能是null 。

Answer 2

在这部分；

          if (snapshot.hasData && snapshot.data.data != null) {
        Call call = Call.fromMap(snapshot.data.data());

        if (!call.hasDialled) {
          return PickupScreen(call: call);
        }
      }

你应该像那样使用这部分；

if (snapshot.hasData && snapshot.data.data() != null) {

除了这个项目，如果你是 flutter 的新手，你不应该尝试制作视频通话应用程序。我知道你从视频中获取了这段代码