FutureBuilder 在显示结果之前显示错误答案

【问题标题】：FutureBuilder shows error before displaying the resultFutureBuilder 在显示结果之前显示错误
【发布时间】：2020-04-25 18:30:29
【问题描述】：

我的futurebuilder 在屏幕上显示错误几秒钟，然后显示结果这是错误日志：

The following NoSuchMethodError was thrown building FutureBuilder<DocumentSnapshot>(dirty, state: _FutureBuilderState<DocumentSnapshot>#fd0c5):
The method '[]' was called on null.
Receiver: null
Tried calling: []("title")

The relevant error-causing widget was: 
  FutureBuilder<DocumentSnapshot> file:///C:/Users/Admin/Desktop/Android/doorstep/lib/domain/repository/booking-repository.dart:7:12
When the exception was thrown, this was the stack: 
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1      BookingRepository.getTitle.<anonymous closure> (package:doorstep/domain/repository/booking-repository.dart:11:39)
#2      _FutureBuilderState.build (package:flutter/src/widgets/async.dart)
#3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4334:27)
#4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4223:15)

代码

Widget getTitle(String id) {
  return FutureBuilder(
    future: Firestore.instance.collection('products').document(id).get(),
    builder: (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot){
      return ListTile(
        title: Text("${snapshot.data['title'].toString()}"),
      );
    }
  );
}

【问题讨论】：

标签： firebase flutter

【解决方案1】：

试试

FutureBuilder<AsyncSnapshot<DocumentSnapshot>>(
        builder: (context, snap) {
          if (snap.connectionState != ConnectionState.done) {
            //print('project snapshot data is: ${snap.data}');
            return Text("loading");
          } else {
            if (snap.hasError) {
              return Text([snap.error.toString()]); 
            }
            else {
              if (snap.hasData) {


                return Text("${snap.data['title'].toString()}");
              } else {
                return Text("No DAta");
              }
            }
          }
        },
        future:
        Firestore.instance.collection('products').document(id).get(),
    );

【讨论】：

这个答案给了我很好的结果，但是由于小部件库导致了一些错误。 FutureBuilder 在从 Firestore 数据库的文档中获取数据库时导致错误。请让我知道如何解决此错误
你能说出确切的错误吗？或者发布一个包含详细信息的新问题并在此处参考。

【解决方案2】：

根据documentation：

，您应该在尝试显示快照之前检查快照是否已有数据

builder: (BuildContext context, AsyncSnapshot snapshot) {
  if (snapshot.hasData) {
    // return something
  } else if (snapshot.hasError) {
    // Manage error
  } else {
    // return something for the user to wait
  }
}

【讨论】：

【解决方案3】：

如果您不向FutureBuilder 的initialData: 参数提供任何数据，当FutureBuilder 被推入小部件树时，您将收到null。

也在FutureBuilder的builder:中

builder: (BuildContext context, AsyncSnapshot snapshot) {
    if(snapshot.hasData){ // <-- check this before using data. true if it has data false if null.

    } else {

    }
}

希望对你有帮助，如有疑问请评论。

【讨论】：