问题描述
我一直在尝试找到一种方法来通过子节点"votes"进行查询,以按"votes"的数量对数据进行排序.我非常确定,因为我将数据存储在Firebase中的方式无法查询,但我目前必须以这种方式存储.
I've been trying to find a way to query by the child node 'votes' to order the data by number of 'votes'. I'm pretty sure because of the way I have stored the data in firebase it cant be queried but I currently have to store it this way.
{
"45" : {
"Biological and Ecological" : {
"Votes" : 1
}
},
"567" : {
"Technology" : {
"Votes" : 2
}
},
"620" : {
"Technology" : {
"Votes" : 1
}
},
"702" : {
"Social and Behavioral" : {
"Votes" : 1
}
}
}
我正在尝试由孩子投票"订购,有没有办法做到这一点?下面是当前显示方法,我知道.OrderbyChild("Votes")不能正确定义路径,但是有办法实现吗?
I am attempting to order by the child "Votes" is there a way to do this? Below is the method in which it is currently displayed I am aware that .OrderbyChild("Votes") isnt defining the path correctly but is there a way to achieve this?
Query query = FirebaseDatabase.getInstance().getReference("CountLikes/").orderByChild("Votes");
query.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot child: dataSnapshot.getChildren()) {
for(DataSnapshot grandchild: child.getChildren()) {
arrayList.add("Project " + child.getKey() + " " + grandchild.getKey() + " " + (String.valueOf(grandchild.child("Votes").getValue(Long.class))));
adapter.notifyDataSetChanged();
}
}}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
throw databaseError.toException();
}
});
推荐答案
这取决于您如何在RealtimeDatabase中实际设置数据模型.在这种情况下,您尝试排序的数据没有统一的路径(看起来是不同的投票类型).
This depends a bit on how you're data model is actually set up in the RealtimeDatabase. In this case, there is not a consistent path to the data you're attempting to sort by (different vote types it seems).
如果您有类似的东西:
CountLikes: [ // collection
docId: { // document
typeOfVote: { // map name
"votes": number // vote count
}
}
]
如果将"votes"与"typeOfVote"分开,则您可以尝试按孩子订购的方式,因为目前您无法通过潜在的通配符按孩子订购(要获得比"Technology"更深的层次).
The way you are trying to order by the child will be possible if "votes" is split up from "typeOfVote" because right now you can't order by child through a potential wildcard (to get a level deeper than "Technology" for example).
CountLikes: [
docId: {
"votes": number,
"type": typeOfVote
}
]
这样,您的orderByChild投票"可能可能有效:)
With this, your orderByChild "votes" could probably work :)
FirebaseDatabase.getInstance().getReference("CountLikes/").orderByChild("votes")
(更新)弗兰克的答案(并阅读评论)显示了orderByChild的另一个示例/更多信息.
(update)This answer by Frank (and read the comments) shows another example/more info for orderByChild.
这篇关于OrderBy查询-我可以由孙子"Vote"订购吗?存储在firebase中?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!