Question

我还是Firebase的新手，还在学习如何做＆＃34;简单＆＃34;有它的东西。我的结构看起来像这样：

"users": {
   "-KY5FJBudXmKv07noYbZ": {
        "emailAddress" : "a@a.com",
        "tags": {
             "red": "8dfhj34sd983ie",
             "green": "9f5d6g8er2d"
        }
    },
   "-KY5JM-NGjNgUXwrBRhs": {
        "emailAddress": "b@b.com",
        "tags": {
             "blue": "58ewgsg656fd",
             "pink": "sdf6g3dg5e6d"
        }
    },
   "-K_0c7wslBiOceF30R-5": {
        "emailAddress": "c@c.com",
        "tags": {
             "blue": "58ewgsg656fd",
             "brown": "xx4f5g68d5d1",
             "black": "8941gs8536sdf1"
        }
    },
}

我想要做的是获取users中包含tags中儿童的节点，其值为58ewgsg656fd。

在此示例中，这将是"blue": "58ewgsg656fd"子节点，并且包含它们的users节点是该结构中的最后两个节点（...0R-5和...BRhs）。< / p>

这是我到目前为止所做的：

DatabaseReference usersRef = database.getReference("users");
usersRef.orderByChild("tags").[NOT SURE WHAT GOES HERE].addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getChildrenCount() == 0) {
            // No users found with that tag
        } else {
            // Users found with that tag
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // Error occurred
    }
});

我应该编写什么代码来获取这些节点？

Answer 1

ArrayList<String> user=new ArrayList<>();
DatabaseReference usersRef=FirebaseDatabse.getInstance().getReference();
usersRef.child("users").addValueEventListener(new ValueEventListener()
{
 public void onDataChange(DataSnapshot dataSnapshot) {
           Iterator<DataSnapshot>iterator=dataSnapshot.getChildren().iterator();
while(iterator.hasNext())
{
 DataSnapshot snapshot=iterator.next();
 if(snapshot.child("tags").child("58ewgsg656fd").exists())
 {
 user.add(snapshot.getKey());
 }
}

 }

 @Override
 public void onCancelled(DatabaseError databaseError) {

        }
});

获取包含具有特定值的子对象的节点

1 个答案: