flutter - Flutter：显示来自firestore的所有用户

问题描述

我想将我的firestore数据库的所有用户显示为列表（尝试开发聊天界面功能），显示设备状态 flutter中有没有可以调用的包来制作聊天界面？

下面我已经尝试到现在：

聊天界面.dart

import 'package:cached_network_image/cached_network_image.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:fluttershare/models/user.dart';
import 'package:fluttershare/widgets/header.dart';
import 'package:fluttershare/widgets/progress.dart';
import 'home.dart';

class Chats extends StatefulWidget {
  final String chatUserId;
  Chats({this.chatUserId});
  @override
  _ChatState createState() => _ChatState(
    chatUserId:this.chatUserId,
  );
}

class _ChatState extends State<Chats> {

  TextEditingController chatController = TextEditingController();

  Future<QuerySnapshot> chatUsers = usersRef.getDocuments();

  final String chatUserId;
  _ChatState({this.chatUserId});
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    userDisplay();
  }
  @override
  Widget build(BuildContext context) {
  }
  userDisplay(){
    return FutureBuilder(
      future: chatUsers,
      builder: (context,snapshot){
        if(!snapshot.hasData){
          return circularProgress();
        }
        List<ChatResult> results = [];
        snapshot.data.documents.forEach((doc){
        User user = User.fromDocument(doc);
        ChatResult result = ChatResult(user);
        results.add(result);
        });
        return ListView(
            children: results,
        );
      }
    );
  }
}

class ChatResult extends StatelessWidget {
  final User user;
  ChatResult(this.user);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: header(context, titleText: 'GupShup'),
      body: Container(
      color:Colors.white,
      child: Column(
        children: <Widget>[
            ListTile(
              leading: CircleAvatar(
                backgroundColor: Colors.grey,
                backgroundImage: CachedNetworkImageProvider(user.photoUrl),
              ),
              title: Text(user.displayName,style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),),
              subtitle: Text('Message'),
              ),
          Divider(
            height: 2.0,
            color: Colors.white54,
          ),
        ],
      ),
    ),
    );
  }
}

我收到此错误

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building Chats(dirty, dependencies: [_InheritedTheme,
_LocalizationsScope-[GlobalKey#4c382]], state: _ChatState#e9c68):
A build function returned null.
The offending widget is:
  Chats
Build functions must never return null.
To return an empty space that causes the building widget to fill available room, return
"Container()". To return an empty space that takes as little room as possible, return
"Container(width: 0.0, height: 0.0)".
The relevant error-causing widget was:
  Chats
[38;5;248m  [39;49m
 lib\widgets\header.dart
When the exception was thrown, this was the stack:
[38;5;244m#0      debugWidgetBuilderValue.<anonymous closure>[39;49m 
 package:flutter/…/widgets/debug.dart
[38;5;244m#1      debugWidgetBuilderValue[39;49m 
 package:flutter/…/widgets/debug.dart
[38;5;244m#2      ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#3      StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#4      Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#5      StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#6      Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#7      SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#8      Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#9      ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#10     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#11     StatelessElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#12     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#13     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#14     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#15     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#16     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#17     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#18     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#19     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#20     StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#21     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#22     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#23     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#24     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#25     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#26     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#27     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#28     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#29     StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#30     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#31     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#32     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#33     StatelessElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#34     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#35     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#36     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#37     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#38     StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#39     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#40     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#41     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#42     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#43     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#44     ProxyElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#45     _InheritedNotifierElement.update[39;49m 
 package:flutter/…/widgets/inherited_notifier.dart
[38;5;244m#46     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#47     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#48     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#49     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#50     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#51     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#52     StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#53     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#54     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#55     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#56     ProxyElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#57     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#58     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#59     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#60     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#61     StatefulElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#62     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#63     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#64     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#65     StatelessElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#66     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#67     SingleChildRenderObjectElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#68     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#69     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#70     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#71     ProxyElement.update[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#72     Element.updateChild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#73     ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#74     StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#75     Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#76     BuildOwner.buildScope[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#77     WidgetsBinding.drawFrame[39;49m 
 package:flutter/…/widgets/binding.dart
[38;5;244m#78     RendererBinding._handlePersistentFrameCallback[39;49m 
 package:flutter/…/rendering/binding.dart
[38;5;244m#79     SchedulerBinding._invokeFrameCallback[39;49m 
 package:flutter/…/scheduler/binding.dart
[38;5;244m#80     SchedulerBinding.handleDrawFrame[39;49m 
 package:flutter/…/scheduler/binding.dart
[38;5;244m#81     SchedulerBinding.scheduleWarmUpFrame.<anonymous closure>[39;49m 
 package:flutter/…/scheduler/binding.dart
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)
════════════════════════════════════════════════════════════════════════════════════════════════════

[38;5;248m════════ Exception caught by widgets library ═══════════════════════════════════[39;49m
[38;5;244mThe following assertion was thrown building Chats(dirty, dependencies: [_InheritedTheme, _LocalizationsScope-[GlobalKey#4c382]], state: _ChatState#e9c68):[39;49m
A build function returned null.

[38;5;244mThe offending widget is: Chats[39;49m
[38;5;244mBuild functions must never return null.[39;49m

[38;5;248mTo return an empty space that causes the building widget to fill available room, return "Container()". To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".[39;49m

[38;5;244mThe relevant error-causing widget was[39;49m
    [38;5;248mChats[39;49m 
 lib\widgets\header.dart
[38;5;244mWhen the exception was thrown, this was the stack[39;49m
[38;5;244m#0      debugWidgetBuilderValue.<anonymous closure>[39;49m 
 package:flutter/…/widgets/debug.dart
[38;5;244m#1      debugWidgetBuilderValue[39;49m 
 package:flutter/…/widgets/debug.dart
[38;5;244m#2      ComponentElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#3      StatefulElement.performRebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m#4      Element.rebuild[39;49m 
 package:flutter/…/widgets/framework.dart
[38;5;244m...[39;49m
[38;5;248m════════════════════════════════════════════════════════════════════════════════[39;49m
Reloaded 0 of 1172 libraries in 197ms.

谁能帮我这个？我想我无法正确调用这些方法。

编辑：我已经稍微改变了我的代码

import 'package:cached_network_image/cached_network_image.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:fluttershare/models/user.dart';
import 'package:fluttershare/widgets/header.dart';
import 'package:fluttershare/widgets/progress.dart';
import 'home.dart';

class Chats extends StatefulWidget {
  final String chatUserId;
  Chats({this.chatUserId});
  @override
  _ChatState createState() => _ChatState(
    chatUserId:this.chatUserId,
  );
}

class _ChatState extends State<Chats> {

  TextEditingController chatController = TextEditingController();

  Future<QuerySnapshot> chatUsers = usersRef.document(currentUser.id).collection('users').limit(100).getDocuments();

  final String chatUserId;
  _ChatState({this.chatUserId});
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    userDisplay();
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: header(context,titleText: 'GupShup'),
      body: chatUsers != null ?  userDisplay() : Text('Users'),
    );
  }
  userDisplay(){
    return StreamBuilder(
      stream: usersRef.document(widget.chatUserId).collection('users').snapshots(),
      builder: (context,snapshot){
        if(!snapshot.hasData){
          return circularProgress();
        }
        List<ChatResult> results = [];
        snapshot.data.documents.forEach((doc){
        User user = User.fromDocument(doc);
        ChatResult result = ChatResult(user);
        results.add(result);
        });
        return ListView(
            children: results,
        );
      }
    );
  }
}

class ChatResult extends StatelessWidget {
  final User user;
  ChatResult(this.user);
  @override
  Widget build(BuildContext context) {
    return Container(
      color:Colors.white,
      child: Column(
        children: <Widget>[
           GestureDetector(
            onTap: () => print('show message'),
            child:
            ListTile(
              leading: CircleAvatar(
                backgroundColor: Colors.grey,
                backgroundImage: CachedNetworkImageProvider(user.photoUrl),
              ),
              title: Text(user.displayName,style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),),
              subtitle: Text('Message'),
              ),
           ),
          Divider(
            height: 2.0,
            color: Colors.white54,
          ),
        ],
      ),
    );
  }
}

现在我的 appBar 出现了一个空白屏幕

编辑后模拟器显示这个

现在有人可以帮助我吗？

标签： flutterdartgoogle-cloud-firestore

flutter - Flutter：显示来自firestore的所有用户

问题描述

解决方案

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