We Keep Coding

How to delete node in firebase android

Hello how can i delete the node in fire_base database using java ?
i have tried this method but it didn't work.
This image show the node struct
the node struct
private void deleteTask (final String userName){
final DatabaseReference reference = FirebaseDatabase.getInstance().getReference("All_USER");
reference.orderByChild("userName").equalTo(userName).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds :dataSnapshot.getChildren()){
String userName = (String) ds.child("userName").getValue();
reference.child(userName).setValue(null);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}

this code is work for me
private void deleteTask (final String userName){
final DatabaseReference reference = FirebaseDatabase.getInstance().getReference("All_USER");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds :dataSnapshot.getChildren()){
if(ds.child("NewUser").child("userName").getValue(String.class).equals(userName)){
ds.child("NewUser").child("userName").getRef().removeValue();
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}

Try this code:
private void deleteTask (final String userName){
final DatabaseReference reference = FirebaseDatabase.getInstance().getReference("All_USER");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds :dataSnapshot.getChildren()){
ds.getRef().orderByChild("userName").equalTo(userName).removeValue();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}

You can just change your code like this :
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (snapshot in dataSnapshot.children) {
snapshot.reference.removeValue()
}
}
}

ArrayAdapter is not working with ListView

Now im trying to create my first Android app.
I'm currently working on a view name Bands which is supposed to create a list (imported from Firebase Database) and link it to a ListView.
As you can see, i have a link to print out the whole bandsList, that way i know the list imported well, and it is...but the ListView is not updated according to the bandsList, so im guessing the problem is in the adapter.
public class Bands extends AppCompatActivity {
ListView listView;
ArrayList<String> bandsList = new ArrayList<>();
ArrayAdapter<String> bandsAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bands);
listView = findViewById(R.id.bandsListView);
bandsAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, bandsList);
listView.setAdapter(bandsAdapter);
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Bands");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot band : dataSnapshot.getChildren()) {
String bandName = band.child("Name").getValue(String.class);
bandsList.add(bandName);
System.out.println("bandsList :" + bandsList);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
databaseReference.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//String BandName =dataSnapshot.getValue(String.class);
for (DataSnapshot band : dataSnapshot.getChildren()) {
String bandName = band.child("Name").getValue(String.class);
System.out.println(bandName);
bandsList.add(bandName);
System.out.println(bandsList);}
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}

Just add bandsAdapter.notifyDataSetChanged() after the Firebase-Callback:
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot band : dataSnapshot.getChildren()) {
String bandName = band.child("Name").getValue(String.class);
bandsList.add(bandName);
System.out.println("bandsList :" + bandsList);
}
bandsAdapter.notifyDataSetChanged();
}

You need to tell the adapter to update the list in both
onDataChange() and onChildAdded() using bandsAdapter.notifyDataSetChanged();

Retrieve Multiple Child branches Firebase

Ok so I have made a CardView hold one database item(in this case a football player) and adapted it in a RecyclerView.
My Firebase Database looks like this:
Players:
|---Goalkeepers:
|--GoalkeeperName
|--(And some other data fields)
|---Defenders:
|---Midfielders:
|---Attackers
My database reference looks like this:
playersDatabase = FirebaseDatabase.getInstance().getReference("Players").child("Goalkeepers");
If I leave the reference as ("Players"), it will give me 4 empty fields representing the Goalkeeper, Defenders, Midfielders and Attackers branch.
How do I display all data from all Position branches such as Goalkeeper, Defenders, Midfielders and Attackers?
Also is there any way of displaying all the players in an organised way with headings in my layout so it looks like this?
Goalkeepers(heading)
Goalkeeper1
Goalkeeper2
Defenders (heading)
Defender1
Defender2
This is the code from the actual app:
public class PlayerList extends AppCompatActivity {
private RecyclerView mPlayerList;
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference playersRef = rootRef.child("Players");
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_squad_list);
//playersDatabase = FirebaseDatabase.getInstance().getReference("Players").child("Goalkeepers");
playersRef.keepSynced(true);
//new code
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String typeOfPlayer = ds.getKey();
Log.d("TAG", typeOfPlayer);
for(DataSnapshot dSnapshot : dataSnapshot.child(typeOfPlayer).getChildren()) {
String player = dSnapshot.getKey();
Log.d("TAG", " " + player);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
playersRef.addListenerForSingleValueEvent(valueEventListener);
mPlayerList = (RecyclerView) findViewById(R.id.my_recycle_view);
mPlayerList.setHasFixedSize(true);
mPlayerList.setLayoutManager(new LinearLayoutManager(this));
}
#Override
protected void onStart() {
super.onStart();
FirebaseRecyclerAdapter<Player, PlayerViewHolder>firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Player, PlayerViewHolder>(Player.class, R.layout.player_row, PlayerViewHolder.class, playersRef) {
#Override
protected void populateViewHolder(PlayerViewHolder viewHolder, Player model, int position) {
viewHolder.setPlayerName(model.getPlayerName());
viewHolder.setPlayerSurname(model.getPlayerSurname());
viewHolder.setPlayerPosition(model.getPlayerPosition());
}
};
mPlayerList.setAdapter(firebaseRecyclerAdapter);
}
public static class PlayerViewHolder extends RecyclerView.ViewHolder{
View mView;
public PlayerViewHolder(View itemView){
super(itemView);
mView = itemView;
}
public void setPlayerName (String playerName){
TextView textViewName = (TextView) mView.findViewById(R.id.textViewName);
textViewName.setText(playerName);
}
public void setPlayerSurname (String playerSurname){
TextView textViewName = (TextView) mView.findViewById(R.id.textViewSurname);
textViewName.setText(playerSurname);
}
public void setPlayerPosition (String playerPosition){
TextView textViewName = (TextView) mView.findViewById(R.id.textViewPosition);
textViewName.setText(playerPosition);
}
}
}
Any help is appreciated. Thanks

To display those players accordingly to the following database structure:
Goalkeepers
Goalkeeper1
Goalkeeper2
Defenders
Defender1
Defender2
Please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference playersRef = rootRef.child("Players");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String typeOfPlayer = ds.getKey();
Log.d("TAG", typeOfPlayer);
DatabaseReference playerRef = playersRef.child(typeOfPlayer);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
String player = dSnapshot.getKey();
Log.d("TAG", " " + player);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
playerRef.addListenerForSingleValueEvent(eventListener);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
playersRef.addListenerForSingleValueEvent(valueEventListener);
Edit:
According to your edited post, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference playersRef = rootRef.child("Players");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String typeOfPlayer = ds.getKey();
Log.d("TAG", typeOfPlayer);
for(DataSnapshot dSnapshot : dataSnapshot.child(typeOfPlayer).getChildren()) {
String player = dSnapshot.getKey();
Log.d("TAG", " " + player);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
playersRef.addListenerForSingleValueEvent(valueEventListener);
Your result must be:
Attackers
Defenders
Goalkeepers
Goalkeeper1
Midfielders

Try this code ..
private void readData(){
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
rootRef.child("Players").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String typeOfPlayer = ds.getKey();
Log.d("TAG", typeOfPlayer);
for(DataSnapshot dSnapshot : dataSnapshot.child(typeOfPlayer).getChildren()) {
String player = dSnapshot.getKey();
Log.d("TAG", " " + player);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
and i hope add internet permission into manifest file..
more information refer this link
https://www.simplifiedcoding.net/firebase-realtime-database-crud/

Firebase retrieve information once user is logged in

I have the following database and need some help retrieving the name and address from the user which is logged in currently.
I wrote the following code but the information is not showing in the textview
public class UserProfileActivity extends AppCompatActivity {
DatabaseReference userReference = FirebaseDatabase.getInstance().getReference();
TextView userName;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_user_profile);
userName = (TextView) findViewById(R.id.userName);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String name = ds.child("name").getValue(String.class);
userName.setText(name);
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
};
}
}
This is what is currently happening when implementing the ValueEventListener

try this:
FirebaseUser user=FirebaseAuth.getInstance().getCurrentUser();
String userid=user.getUid();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child(userid);
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String address=dataSnapshot.child("address").getValue().toString();
String name=dataSnapshot.child("name").getValue().toString();
userName.setText(name);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Since your datasnapshot is on the child(userid) which is direct child under root node then you don't need to iterate to be able to get the values of the current user.

Fetching values from firebase based on key

This is the structure of the database
I need to fetch all the values of "QNGGvYL7dgde9Oypi9a4IFdAys03"
I have tried this code but it's not working
String uid = FirebaseAuth.getInstance().getUid();
DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReference();
Query query = databaseRef.child("bookmarks").equalTo(FirebaseAuth.getInstance().getUid());
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
vehicleList.add(postSnapshot.getValue().toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

If you know the key you want to get, you don't need a query:
DatabaseReference ref = databaseRef.child("bookmarks").child(FirebaseAuth.getInstance().getUid());
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
vehicleList.add(postSnapshot.getValue().toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errorrs
}
});