查询获得前10名最高分 [英] query for getting top 10 highest scores

问题描述

我在我的android应用程序中使用了firebase，我的树看起来像这样

  data>坦克> username1>杀死= 1，尝试= 3 
> username5>杀死= 5，尝试= 13 
> username7>杀= 3，试= 7 
> username2>杀死= 6，尝试= 4 
 
数据>大炮> username9>杀死= 31，尝试= 33 
> username7>杀死= 15，尝试= 13 
> username3>杀死= 13，尝试= 77 
> username6> kills = 66，tries = 44 
  

我要做的是向用户显示前10个用户名杀死大炮或坦克（取决于哪一个用户选择），但我似乎无法找到一个解决方案。

起初我认为解决方案将是像

  ref.child（data / tanks）。orderbyChild（kill）
  

但似乎不起作用，问题是它不会返回杀死子元素。它返回我已经可以访问的坦克的整个树。我想要的是如果可能的话，得到所有杀死孩子的名单？我不知道我怎么能得到最高的杀伤力，因为没有办法知道哪些用户名在坦克或大炮，除非我遍历所有的用户名。

>任何人都可以帮我解决这个问题吗？

解决方案

DatabaseReference myref = FirebaseDatabase.getInstance ）.getReference（）chield（ 罐）。
myref.addListenerForSingleValueEvent（new ValueEventListener（）{
@Override $ b $ public void onDataChange（DataSnapshot dataSnapshot）{

$ b $ userlist = new ArrayList< String> （）;

Toast.makeText（DataFromFirebase.this，no of usersare+ dataSnapshot.getChildrenCount（），Toast.LENGTH_LONG）.show（）;
// String value =（ （DataSnapshot dsp：dataSnapshot.getChildren（））{
userlist.add（String.valueOf（String））dataSnapshot.getValue（）;

//结果将被保留在这里
（dsp.getKey（）））; /
}
@Override
public void onCancelled（DatabaseError firebaseError）{





使用上面的代码，您可以获得tank中的所有用户，然后对所有用户引用重复此操作， / p>

I am using firebase in my android application and my tree looks like this

data > tanks > username1 > kills = 1, tries = 3
             > username5 > kills = 5, tries = 13
             > username7 > kills = 3, tries = 7
             > username2 > kills = 6, tries = 4

data > cannons > username9 > kills = 31, tries = 33
               > username7 > kills = 15, tries = 13
               > username3 > kills = 13, tries = 77
               > username6 > kills = 66, tries = 44

what i am trying to do is show the user the top 10 usernames with the highest kills for cannons or tanks (depending on which one the user selects) but i cant seem to find a solution.

At first i thought the solution would be like

ref.child("data/tanks").orderbyChild("kills")

but it doesn't seem to work the problem is that it doesn't return the "kills" child. it returns the whole tree of the tank which i can already access. What i want is to get a list of all "kills" child if that's possible? And i am not sure how else can i get the highest kills because there's no way of knowing which of the usernames are in tanks or cannons unless i iterate through all of the usernames.

Can anyone help me with this?

解决方案

         DatabaseReference myref= FirebaseDatabase.getInstance().getReference().chield("tanks");
         myref.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {


            userlist= new ArrayList<String>();

            Toast.makeText(DataFromFirebase.this, "no of usersare " + dataSnapshot.getChildrenCount(), Toast.LENGTH_LONG).show();
            //String value = (String) dataSnapshot.getValue();

            // Result will be holded Here
            for (DataSnapshot dsp : dataSnapshot.getChildren()) {
                userlist.add(String.valueOf(dsp.getKey())); /
                 }
           @Override
              public void onCancelled(DatabaseError firebaseError) {

             }
          }

using above code you get the all users in tanks chield then repeat this for all user references then get all kill values

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