The question is published on by Tutorial Guruji team.
Context
Hello, I am trying to update an element of a node in firebase with android, the problem is that as seen in the structure of my database,
I have a node called “comment” and within it another node with a post id and inside the Post ID node is the comment ID.
issue
I do not know how I can update all the nodes that meet certain encodings, since I cannot put an exact path since this would only update one node and I want to update all the nodes that meet the condition of the query as seen in the code.
final DatabaseReference CommentDB = FirebaseDatabase.getInstance().getReference("Comment");
Query quersy = CommentDB.orderByChild("uname").equalTo(currentUsers.getDisplayName());
quersy.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()){
String key = ds.getKey();
HashMap<String, Object> maps = new HashMap<>();
maps.put("uimg", ""+mUri);
sd.child(key).updateChildren(maps);
Answer
Your uname is nested under two dynamic levels. Firebase Realtime Database can only order/filter on values that are at a fixed path under one dynamic level.
So you will have to either change data structure to be a flat list under /Comment or read all data under /Comment and filter client-side.
final DatabaseReference commentDB = FirebaseDatabase.getInstance().getReference("Comment");
commentDB.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot level1Snapshot : dataSnapshot.getChildren()){
for(DataSnapshot level2Snapshot : level1Snapshot.getChildren()){
if (currentUsers.getDisplayName().equals(level2Snapshot.child("uname").getValue(String.class)) {
Log.i("Firebase", "Updating "+level1Snapshot.getKey()+"/"+level2Snapshot.getKey());
level2Snapshot.getRef().child("uimg").setValue(mUri);
}
}
}
}
...