使用Flutter的多用户应用程序

本文介绍了使用Flutter的多用户应用程序的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在处理一个有多个用户的应用程序.我有一个资源列表，这个资源列表就像一个巧克力列表(只有一个并且是唯一的).现在，我在所有活动用户的主屏幕上显示此巧克力.现在，用户可以单击巧克力，它将被提供给他们.但是，当发生这种情况时，我想刷新所有已登录的用户，以确保没有两个用户使用相同的巧克力.

I am working on one application which has multiple users. I have a list of resources, this list of resources are like a list of chocolates (only one and unique). Now, I am showing this chocolates on the home screen of all active users. Now, user can click on chocolate and it will be given to them. But, when this happens i want to refresh all logged in users so to ensure that no two users are having same chocolate.

我正在使用数据库触发器来监视数据库中的更改.我能够做到这一点，但我关心的是如何刷新listView.

I am using database trigger to monitor the change in DB. I am able to do that but my concern is how to refresh listView.

我的算法如下:

1)监视数据库中的更改.2)获取新的数据集.3)更新视图

1) Monitor changes in Database. 2) Get Fresh set of data. 3) Update View

我尝试如下创建syncDatabaseFunction:

I tried creating syncDatabaseFunction as below:

Future syncDatabaseFunction() async { CollectionReference reference = Firestore.instance.collection('Chocolates'); reference.snapshots().listen((querySnapshot){ querySnapshot.documentChanges.forEach((change){ print("Changed Chocolate"); BackendOperations.getAllChocolates().then((value){ var chocolateTemp = (value as List<ChocolateModel>) .where((element) => (element.chocolateColor == "Brown")) .toList(); print("Count is "); return chocolateTemp; }); }); }); }

对于列表视图，我正在使用futureBuilder.

For listview I am using futureBuilder.

推荐答案

我认为，如果您使用 StreamBuilder ，则可以解决问题.当用户删除或添加新评论时，它将向所有用户显示. StreamBuilder 就是这样做的，是Stream的观察者.

I think that if you use StreamBuilder you will solve the problem. When a user remove or add a new Comment it show for all users. StreamBuilder was made to do this, be a Observer of the Stream.

这是我的代码:

Widget getListComment() { return StreamBuilder<QuerySnapshot>( stream: Firestore.instance .collection('comments') .where('post', isEqualTo: postRef) .orderBy('createdAt', descending: true) .snapshots(), builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) { if (snapshot.hasError) return new Text('Error: ${snapshot.error}'); switch (snapshot.connectionState) { case ConnectionState.waiting: return Column( children: <Widget>[ CircularProgressIndicator(), ], ); default: return new ListView( children: snapshot.data.documents.map((DocumentSnapshot document) { return CommentItem( key: Key(document.documentID), comment: Comment.fromDoc(document), myUser: widget.myUser, ); }).toList(), ); } }, ); }

我收到Firebase的评论，并显示在 ListView 中，我认为这就像您的巧克力.

I receive comments from Firebase and show in a ListView, I think that is like your chocolates.