firebase - Flutter：如何在 Firestore 数据库中获取项目的子项

Question

嗨，我有一个 Firestore 数据库，如下所示：

我试图让数据循环遍历每个聊天并将数据添加到可见性仪表板小部件中，作为聊天的名称和发送的最后一条消息，因此应用程序希望像这样丢失。

这是我尝试过的代码，我已经四处寻找如何做到这一点，但我只能在 Java 中找到解决方案。

StreamBuilder<QuerySnapshot>(
          stream: _firestore.collection('dashboard').snapshots(),
          builder: (context, snapshot){
            if(!snapshot.hasData){

            }else{
              final dashboards = snapshot.data.documents;
              List<Dashboard> dashboardList = [];
              for (var dashboard in dashboards){

                final String nameOfChat = dashboard.data['chats']['nameOfChat'];
                final String lastMessageSent = dashboard.data['chats']['lastMessageSent'];

                final String username = dashboard.data['displayDashboardTo'];
                final String displayDashboardToUID = dashboard.data['uid'];

                dashboardCard = Dashboard(
                  nameOfChat: nameOfChat,
                  lastMessageSent: lastMessageSent,
                  displayDashboardTo: username,
                );

                dashboardList.add(dashboardCard);

              }

              return Visibility(
                visible: true, 
                child: Expanded(
                  child: ListView(
                    children: dashboardList,
                  ),
                ),
              );
            }
          }
        ),

谢谢。

标签： firebaseflutterdartgoogle-cloud-firestore

Answer 1

由于“聊天”字段是一个数组，因此您必须遍历它。

final dashboards = snapshot.data.documents;
List<Dashboard> dashboardList = [];
for (var dashboard in dashboards){
final Map data = dashboard.data;

var chats = data['chats'];

for(var chat in chats) {
  final String nameOfChat = chat['nameOfChat'];
  final String lastMessageSent = chat['lastMessageSent'];
  final String username = chat['displayDashboardTo'];
  final String displayDashboardToUID = chat['uid'];

  dashboardCard = Dashboard(
   nameOfChat: nameOfChat,
   lastMessageSent: lastMessageSent,
   displayDashboardTo: username,
 );

dashboardList.add(dashboardCard);

});

}