Flutter Firestore获取数据接收器:空错误 [英] Flutter firestore getting data receiver: null error

问题描述

我进行了很多搜索，但找不到解决方案.我需要你的帮助.

I searched a lot but couldn't find a solution. I need your help.

在我的数据库模型中，我有一个像这样的方法来获取数据:

In my database model, I have a method like this to get the data:

  Future<Map<String,dynamic>> getSystemSettings() async {
    var response = await _firestore.collection("system").doc("settings").get();
    return response.data();
  }

稍后，我想以Map< String，dynamic>的形式使用数据.从类中，我想通过调用以下方法从中获取数据.

Later, I want to use the data in the form of Map <String, dynamic> from the class I want to get the data from by calling the method as follows.

  getValues() {
    database.getSystemSettings().then((value) {
    print("value");
    print(value);
  });

我希望看到我的地图< String，动态>在第二个代码块中键入数据代替值，但是出现以下错误.

What I expect is to see my Map <String, dynamic> type data in place of value in the second code block, but I get the following error.

方法'sistemAyarlariniAl'在null上被调用.

The method 'sistemAyarlariniAl' was called on null.

接收方:空

尝试调用:sistemAyarlariniAl()

Tried calling: sistemAyarlariniAl()

您能帮我吗?我在哪里做错了?

Can you help me with this? Where am I doing wrong?

推荐答案

尝试一下

  Future getPosts() async {
        var firestore = Firestore.instance;
        QuerySnapshot qn = await firestore.collection("system").getDocuments();
        return qn.documents;
      }

或者您可以使用Stream Builder访问Firebase中的数据.

Or You can use Stream Builder to access data from firebase.

首先，您需要安装 cloud_firestore 库

    dependencies:
          cloud_firestore: ^0.14.4

然后导入

    import 'package:cloud_firestore/cloud_firestore.dart';

然后需要构建StreamBuilder

then need to build StreamBuilder

StreamBuilder(
       stream: Firestore.instance
                 .collection('system')
                 .document(users.uid)
                 .snapshots(),
       builder: (context, snapshot){
                if (snapshot.hasData) {
                  return Container())

您可以像这样访问数据库值

You Can access your database values like this

 snapshot.data['settings'].toString()

TextField中的示例

Example in TextField

Text(
       snapshot.data['settings'].toString(),
       style: TextStyle(
              fontSize: 20,
              decorationThickness:2,
              fontWeight:
              FontWeight.w500,
              color:Colors.black87)
    ),

这篇关于Flutter Firestore获取数据接收器:空错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！