Develop Reference

Firebase Realtime Database delete item in List

I have the data stored in the Realtime Database in this format:
If I wanted to delete one of the entries in the list named 7P3MRvkC2FQkwcyC7CYVWZP9Ps72, I use this code.
The id under this is generated automatically:
FirebaseDatabase.getInstance()
.getReference()
.child("users")
.child(id) -------------------> unique id
.orderByChild("orderId")
.equalTo(orderId,"orderId")
.getRef()
.removeValue();
But this deletes the complete list of users.

Try this code
DatabaseReference ref = FirebaseDatabase.getInstance()
.getReference()
.child("users")
.child(id);
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
dataSnapshot.getRef().removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
// notify
}
});
}

But this deletes the complete list of users.
That's the expected behavior. If you need to remove only the elements where the orderId property holds the value of a particular "orderId", then you should iterate trough the results like in the following lines of code:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("users");
DatabaseReference uidRef = usersRef.child(uid);
Query query = uidRef.orderByChild("orderId").equalTo(orderId);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
ds.getRef().removeValue();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("TAG", databaseError.getMessage()); //Don't ignore potential errors!
}
};
query.addListenerForSingleValueEvent(valueEventListener);

How to get the names of the json columns from firebase? I leave an example below my question

I would like to list the names of the dates, such as 24_1_2020, 25_1_2020, etc ...

Assuming that teLm ... IWV2 is the uid of the authenticated user, to display only those keys 24_1_2020, 25_1_2020, please use the following lines of code:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("Mensaje").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String key = ds.getKey();
Log.d(TAG, key);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);
See, I have used the getChildren() method to loop through the DataSnapshot object, which basically contains all children under the uid node. Calling getKey(), you can get each key that is corresponding to each child.
If teLm ... IWV2 is not the uid of the authenticated user, then simply add that String directly in your reference:
DatabaseReference uidRef = rootRef.child("Mensaje").child("teLm ... IWV2");

Retrieve specific value from Firebase database into string variable

I'm trying to retrieve a specific value from a Firebase realtime Database.
The data looks like this:
I want to get the URL value from any of them and then put it into a string variable to use later. This is so that the program does not need to be changed if the download link is changed. The code I have so far is;
DatabaseReference fdb = FirebaseDatabase.getInstance().getReference();
//Query query = fdb.child("URLDOWNLOADS").child("WSSeasons")
fdb.addListenerForSingleValueEvent(new ValueEventListener()
{
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot)
{
for (DataSnapshot url : dataSnapshot.getChildren())
{
LoginInfoFirebasedb DownURL = url.getValue(LoginInfoFirebasedb.class);
String temp = DownURL.dwldURL;
URL1 = temp;
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError)
{
}
});
Some help would be seriously appreciated. I understand this may be a simple problem but I am stumped.

To get each url as a String, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("URLDOWNLOADS");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String key = ds.getKey();
String url = ds.child("URL").getValue(String.class);
Log.d(TAG, key + " / " + url);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
ref.addListenerForSingleValueEvent(valueEventListener);

How to show datas on a ListView when it has multiple child in Firebase database as shownin picture

So please look at the problem iam facing.

Assuming that the SuccessfulOrders node is a direct child of your Firebase database root, to get that data and add it into a list, please use the following code:
String phoneNo = FirebaseAuth.getInstance().getCurrentUser().getPhoneNumber();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference phoneNoRef = rootRef.child("SuccessfulOrders").child(phoneNo);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
ListView<String> list = new ArrayList<>();
for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
for(DataSnapshot ds : dSnapshot.getChildren()) {
String productName = ds.child("productName").getValue(String.class);
list.add(productName);
Log.d("TAG", productName);
}
//Do what you need to do with your list.
Log.d("TAG", list.toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
phoneNoRef.addListenerForSingleValueEvent(valueEventListener);
The output in your logat wil be:
1000 Website Visit
SOCIAL MEDIA PACK
//and so on

Retrieve all data from Firebase Database

ANDROID: I have a Firebase database like this.
In my app, I would like to compile an arraylist that displays all values from the nameofEntry [DESCRIBED BELOW]. By this I mean the "balso," the "nairboh" and so on.
I have the references:
DatabaseReference root = FirebaseDatabase.getInstance().getReference();
DatabaseReference users = root.child("Users");
DatabaseReference childRef = users.child(userID);
DatabaseReference childRefNameNode = childRef.child(nameOfEntry);
childRefNameNode.child(nameOfEntry).setValue(nameOfEntry);
//FETCH DATA
childRefNameNode.child(nameOfEntry).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String valueFromDB = dataSnapshot.getValue(String.class);
Log.i("Jimit", valueFromDB);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
But this only fetches for one entry. How can I get more entries? [All of them]?

You need to use this code snippet. You haven't used any for loop to step over your children.
EDIT: Also, update your database reference as:
//Updated ref
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Users").child(userID);*
//add listener to updated ref
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
//use the for loop here to step over each child and retrieve data
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()){
String valueFromDB = childSnapshot.getValue(String.class);
Log.i("Jimit", valueFromDB);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Do let me know if it changes anything for you.