如何使用Flutter从Firestore中使用ListView获得无限滚动

Question

我正在Flutter中使用Firestore和ListView。 对于列表中的某些项目，每种方法都可以正常工作，但是我向下滚动的距离超出了所看到的限制，我收到了许多消息：“该方法在null上调用”。 似乎ListView.builder不能正确处理Firebase或类似的所有日期请求。

这是代码：

import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:father_home_flutter/screen_audio_selected.dart';
import 'package:father_home_flutter/model/utils.dart';

class AudioScreenList extends StatelessWidget {
  static const String _collectionRussian = 'speech-ru';
  static const String _loadingTextRussian = 'Loading...';
  static const String _speechTitle = 'speechTitle';
  static const String _speechSubtitle = 'speechSubtitle';
  static const String _audioLink = 'audioLink';
  static const String _pastorCode = 'pastorCode';
  static const String _pastorName = 'pastorName';
  static const String _id = "id";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: StreamBuilder(
            stream: Firestore.instance
                .collection(_collectionRussian)
                .limit(100)
                .orderBy(_id, descending: true)
                .snapshots(),
            builder: (context, snapshot) {
              if (!snapshot.hasData)
                return const Center(
                    child: Text(
                  _loadingTextRussian,
                  style: TextStyle(fontSize: 25.0, color: Colors.grey),
                ));
              return ListView.builder(
                itemCount: snapshot.data.documents.length,
                itemBuilder: (BuildContext context, int i) =>
                    _buildRow(context, snapshot.data.documents[i]),
              );
            }));
  }

  Widget _buildRow(BuildContext context, DocumentSnapshot document) {
    return Container(
        margin: const EdgeInsets.fromLTRB(0.0, 8.0, 0.0, 0.0),
        height: 90.0,
        child: ListTile(
            leading: Padding(
                padding: EdgeInsets.fromLTRB(0.0, 20.0, 0.0, 0.0),
                child: Hero(
                    tag: document[_audioLink],
                    child: new ClipOval(
                        child: Container(
                      width: 70.0,
                      height: 70.0,
                      child: Image.asset(
                        Utils.getImagePastor(document[_pastorCode]),
                        fit: BoxFit.cover,
                      ),
                    )))),
            title: Text(document[_speechTitle]),
            subtitle:
                Text(document[_speechSubtitle] + " - " + document[_pastorName]),
            onTap: () => onPressed(context, document[_speechTitle],
                document[_pastorCode], document[_audioLink])));
  }

  onPressed(BuildContext context, String speechTitle, String pastorCode,
      String audioLink) {
    Navigator.push(
        context,
        MaterialPageRoute(
            builder: (context) =>
                ScreenAudioSelected(speechTitle, pastorCode, audioLink)));
  }
}

这是模拟器上的问题：

我在网上寻找如何处理它的方法，但是我发现了一些模拟服务器请求的示例，例如https://flutter-academy.com/flutter-listview-infinite-scrolling/

任何人都面临过同样的问题，或者对如何解决有想法？

Answer 1

好的，在网上查看后，借助此链接，我找到了一种解决此问题的方法

如果有人需要，我在这里写下完整的代码：

    class AudioScreenList extends StatefulWidget {
  @override
  _AudioScreenListState createState() => _AudioScreenListState();
}

class _AudioScreenListState extends State<AudioScreenList> {
  bool isPerformingRequest = false;

  static const String _collectionRussian = 'speech-ru';
  static const String _loadingTextRussian = 'Loading...';
  static const String _speechTitle = 'speechTitle';
  static const String _speechSubtitle = 'speechSubtitle';
  static const String _audioLink = 'audioLink';
  static const String _pastorCode = 'pastorCode';
  static const String _pastorName = 'pastorName';
  static const String _id = "id";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: StreamBuilder(
            stream: Firestore.instance
                .collection(_collectionRussian)
                .orderBy(_id, descending: true)
                .snapshots(),
            builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {
              if (!snapshot.hasData)
                return const Center(
                    child: Text(
                  _loadingTextRussian,
                  style: TextStyle(fontSize: 25.0, color: Colors.grey),
                ));
              return ListView(children: getExpenseItems(snapshot));
            }));
  }

  getExpenseItems(AsyncSnapshot<QuerySnapshot> snapshot) {
    return snapshot.data.documents
        .map((doc) => new Container(
            margin: const EdgeInsets.fromLTRB(0.0, 8.0, 0.0, 0.0),
            child: ListTile(
                leading: Padding(
                    padding: EdgeInsets.fromLTRB(0.0, 20.0, 0.0, 0.0),
                    child: Hero(
                        tag: doc[_audioLink],
                        child: new ClipOval(
                            child: Container(
                          width: 70.0,
                          height: 70.0,
                          child: Image.asset(
                            Utils.getImagePastor(doc[_pastorCode]),
                            fit: BoxFit.cover,
                          ),
                        )))),
                title: new Text(doc[_speechTitle]),
                subtitle: new Text(doc[_speechSubtitle].toString() +
                    " - " +
                    doc[_pastorName].toString()),
                onTap: () => onPressed(context, doc[_speechTitle],
                    doc[_pastorCode], doc[_audioLink]))))
        .toList();
  }

  onPressed(BuildContext context, String speechTitle, String pastorCode,
      String audioLink) {
    Navigator.push(
        context,
        MaterialPageRoute(
            builder: (context) =>
                ScreenAudioSelected(speechTitle, pastorCode, audioLink)));
  }
}