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How can I change the value of child in Firebase database?

I want to change the value of child "toggleStatus" under Reference "BetSlip" as shown below. The already set value is "on" so I want such that when I click the button the value of "toggleStatus" is changed to "off"
BetSlipActivity.toggleCollapse.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String timeStamp = betSlip.get(position).getTimeStamp();
String toggleStatus = betSlip.get(position).getToggleStatus();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("BetSlip");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot ds: snapshot.getChildren()) {
String timestamp = ""+ ds.child("timeStamp").getValue();
String toggleStatus = ""+ ds.child("toggleStatus").getValue();
if (timeStamp.equals(timestamp) && toggleStatus.equals("on")) {
//set value to off
}
if (timeStamp.equals(timestamp) && toggleStatus.equals("off")) {
//set value to on
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
});

If you've got the DataSnapshot for a path in the database, it's easy to get the DatabaseReference that you need to update it:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("BetSlip");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot ds: snapshot.getChildren()) {
String timestamp = ""+ ds.child("timeStamp").getValue();
String toggleStatus = ""+ ds.child("toggleStatus").getValue();
if (timeStamp.equals(timestamp) && toggleStatus.equals("on")) {
ds.child("toggleStatus").getRef().setValue("off");
}
if (timeStamp.equals(timestamp) && toggleStatus.equals("off")) {
ds.child("toggleStatus").getRef().setValue("on");
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
throw error.toException(); // never ignore errors
}
});
Since you're updating the node based on its existing value, strictly speaking you might need to use a transaction for it.

Firebase Database Not in Sync

I want to keep the addToCart button in sync with the Firebase database. The button should be enabled if the checkForActiveOrdersQuery has no children, otherwise, it should be disabled.
The issue with the below code is that the keepSynced(true) is not working.
checkForActiveOrders = FirebaseDatabase.getInstance().getReference("activeOrders");
checkForActiveOrdersQuery = checkForActiveOrders.child(restaurantID).child(tableID);
checkForActiveOrdersQuery.keepSynced(true);
checkForActiveOrdersQuery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
String orderIDKey = dataSnapshot1.getKey();
if (!dataSnapshot.hasChildren()) {
addToCartButton.setEnabled(true);
} else if (!orderIDKey.equals(orderID)){
addToCartButton.setEnabled(false);
} else if (orderIDKey.equals(orderID)) {
addToCartButton.setEnabled(true);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

Get data from firebase from a specific position

Hy, I'm writing an application that has to get specific data from firebase using the position of the item in the listView. My problem is that I have no idea how to take it this item on firebase.
For all child of Torneo I have to control all the nameCreator.
I have tried this:
public Boolean RegisterUser(Data data, final int position, final Context c){
boolean registration;
final ArrayList<String> Creator = new ArrayList<>();
databaseReference.orderByChild("Tornei").equalTo(Integer.toString(position)).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot datas: dataSnapshot.getChildren()){
Creator.add(data.child("nameCreator").getValue().toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
if(Creator.equals(data.getNameCreator())){
registration = false;
}else{
registration = true;
}
return registration;
}
Data is a class with some getter and setter that I have created.
position is the position of the element on the list view.
Thanks for answers.

Change the following:
databaseReference.orderByChild("Tornei").equalTo(Integer.toString(position)).addListenerForSingleValueEvent(new ValueEventListener() {
into this:
databaseReference.child("Tornei").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot datas: dataSnapshot.getChildren()){
Creator.add(datas.child("nameCreator").getValue().toString());
if(Creator.equals(data.getNameCreator())){
registration = false;
}else{
registration = true;
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Then you will be able to loop and retrieve the value of nameCreator

It's easy.
【Step 1 | Get Snapshot Data and Save in Global Variable】
DatabaseReference rootReference = FirebaseDatabase.getInstance().getReference();
DatabaseReference fruitsReference = rootReference.child("fruits");
DataSnapshot fruitsData;
#Override
protected void onStart() {
super.onStart();
fruitsReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshots) {
fruitsData = dataSnapshots;
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
【Step 2 | Find Your Target Position through the Loop】
public void onClick(View view) {
int index = 0;
for (DataSnapshot childSnapshot : fruitsData.getChildren()) {
if (index == 1) { //your target position
DatabaseReference currentFruitReference = childSnapshot.getRef();
currentFruitReference.setValue("peach"); //do whatever you want
}
index++;
}
}

Data retrieving error while i want to get all child from a certain Key

I want to read some specific child from the parent-child, by getchild() function but this will not work properly.
FirebaseUser FUser = mAuth.getCurrentUser();
String userid = FUser.getUid();
DatabaseReference DR;
DR = FirebaseDatabase.getInstance().getReference().child("HistoryTable").child(userid);
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
// Iterable<DataSnapshot> root = dataSnapshot.getChildren();
// Toast.makeText(getApplicationContext(), "ds "+dataSnapshot.getChildren(),Toast.LENGTH_LONG).show();
for (DataSnapshot ds: dataSnapshot.getChildren()) {
// Toast.makeText(getApplicationContext(), "ds "+ds,Toast.LENGTH_LONG).show();
for (DataSnapshot d: ds.getChildren()) {
String Height = d.getKey() + d.getValue() + "\n".toString();
String ch = d.child("1Height:").getValue(String.class);
// tv.append(Height);
tv.append(ch);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
I want to get this four child from every key.

you have to add your push id in reference :-
DR = FirebaseDatabase.getInstance().getReference().child("HistoryTable").child(userid).child("push id");
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
// Iterable<DataSnapshot> root = dataSnapshot.getChildren();
// Toast.makeText(getApplicationContext(), "ds "+dataSnapshot.getChildren(),Toast.LENGTH_LONG).show();
for (DataSnapshot ds: dataSnapshot.getChildren()) {
// Toast.makeText(getApplicationContext(), "ds "+ds,Toast.LENGTH_LONG).show();
for (DataSnapshot d: ds.getChildren()) {
String Height = d.getKey() + d.getValue() + "\n".toString();
String ch = d.child("1Height:").getValue(String.class);
// tv.append(Height);
tv.append(ch);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

Try like this if you just want to read the value. if you want to read data only once use addListenerForSingleValueEvent()
*Try to read values by object stucture https://firebase.google.com/docs/database/android/read-and-write#basic_write
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot d: ds.getChildren()) {
//below line may cause null pointer Exception
String Height = d.getKey() + d.getValue() + "\n".toString();
if(d.child("1Height:").getValue()!=null){
String ch = d.child("1Height:").getValue(String.class);
//tv.append(Height);
tv.append(ch);}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

To get the value of your 4UserId property, simply use the following lines of code:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("HistoryTable").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String userId = ds.child("4UserId").getValue(String.class);
Log.d(TAG, userId);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);
The result in your logcat will be:
2Wwrjx...P2obFO83

Why am I receiving empty strings after receiving valid data from Firebase?

Using Firebase, I'm trying to display to the user people they have matched with. I already have valid data for testing this and I have already run tests with sample data to see if everything else works.
Now, when I use real data from Firebase, problems occur.
This is what I have for code:
public String username = "";
public String profileImage = "";
public String discussion = "";
private void FetchMatchInformation(final String key, final String choice) {
DatabaseReference matchDb = FirebaseDatabase.getInstance().getReference().child("answers").child(key);
matchDb.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
String opposite = postSnapshot.getValue(String.class);
if(opposite.equals("agree") && choice.equals("disagree")) {
DatabaseReference found = FirebaseDatabase.getInstance().getReference().child("users").child(postSnapshot.getKey());
found.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
if(postSnapshot.getKey().equals("username")) {
username = postSnapshot.getValue(String.class);
}
if(postSnapshot.getKey().equals("providerId")) {
String provider = postSnapshot.getValue(String.class);
if(provider.equals("google.com")) {
Uri photoUrl = FirebaseAuth.getInstance().getCurrentUser().getPhotoUrl();
String originalPieceOfUrl = "s96-c/photo.jpg";
String newPieceOfUrlToAdd = "s400-c/photo.jpg";
String photoPath = photoUrl.toString();
String newString = photoPath.replace(originalPieceOfUrl, newPieceOfUrlToAdd);
profileImage = newString;
} else if(provider.equals("facebook.com")) {
profileImage = FirebaseAuth.getInstance().getCurrentUser().getPhotoUrl().toString() + "?type=large";
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
FirebaseDatabase.getInstance().getReference().child("debates").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
if(postSnapshot.getKey().equals(key)) {
discussion = postSnapshot.getValue(String.class);
break;
}
break;
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
MessagesObject objDisc = new MessagesObject(username, discussion, profileImage);
resultsMessages.add(objDisc);
mMessagesAdapter.notifyDataSetChanged();
} else if(opposite.equals("disagree") && choice.equals("agree")) {
DatabaseReference found = FirebaseDatabase.getInstance().getReference().child("users").child(postSnapshot.getKey());
found.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
if(postSnapshot.getKey().equals("username")) {
username = postSnapshot.getValue(String.class);
}
if(postSnapshot.getKey().equals("providerId")) {
String provider = postSnapshot.getValue(String.class);
if(provider.equals("google.com")) {
Uri photoUrl = FirebaseAuth.getInstance().getCurrentUser().getPhotoUrl();
String originalPieceOfUrl = "s96-c/photo.jpg";
String newPieceOfUrlToAdd = "s400-c/photo.jpg";
String photoPath = photoUrl.toString();
String newString = photoPath.replace(originalPieceOfUrl, newPieceOfUrlToAdd);
profileImage = newString;
} else if(provider.equals("facebook.com")) {
profileImage = FirebaseAuth.getInstance().getCurrentUser().getPhotoUrl().toString() + "?type=large";
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
FirebaseDatabase.getInstance().getReference().child("debates").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
if(postSnapshot.getKey().equals(key)) {
discussion = postSnapshot.getValue(String.class);
break;
}
break;
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
MessagesObject objDisc = new MessagesObject(username, discussion, profileImage);
resultsMessages.add(objDisc);
mMessagesAdapter.notifyDataSetChanged();
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
So what's happening is I'm getting the user's username, their profile image, and figuring out the value, which I called discussion after determining the valid key. These values are all being accessed from different tree structures from the same real-time database.
Now, at the end of the if or else-if statement, I create and instantiate the MessagesObject by passing in the username, profile image, and discussion variables. I then add this object to the List<MessagesObject> called resultMessages. I then notify my custom adapter mMessagesAdapter that the data has changed.
Like I said, all the other pieces of code work perfectly fine. It's just when I pass username, discussion, and profileImage it always passes an empty string. I know this from using the debugger.
Why is that? It should not be doing that.