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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) {
}
});

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

How to retrieve this data from firebase database

I want to get to a listview the data on "Categorias" folder, but i try everthing and i can't do this.
Fragment code:
myRef.addValueEventListener(new ValueEventListener() {
public static final String TAG = "TNW";
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
Map<String, Object> td = (HashMap<String,Object>) dataSnapshot.getValue();
list3 values = td.values();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getActivity().getApplicationContext(), "Ese usuario ya existe ", Toast.LENGTH_SHORT).show();
}
});

Its very simple, here is the code to fetch your values.
DatabaseReference db = FirebaseDatabase.getInstance().getReference("people");
db.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds: dataSnapshot.getChildren()){
//get the categorias node
DataSnapshot dsCategorias = ds.child("categorias");
//loop inside the categorias node for all children
for(DataSnapshot dbValSnapshot: dsCategorias.getChildren()){
//Assuming all children have only boolean values
//getting the key and the values
String key = dbValSnapshot.getKey();
boolean value = dbValSnapshot.getValue(Boolean.class);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Let me know if you are not able to understand any part of my code. Thanks

Model Class returns null

[model class is returning null, data is coming from Firebase database but upon getting imageUrl its giving null.
Actually, I am trying to get images urls from database which are previously saved.
firebaseDatabase=FirebaseDatabase.getInstance();
databaseReference=firebaseDatabase.getInstance().
getReference("Catagories");
mupload=new ArrayList<>();`
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot post : dataSnapshot.getChildren())
{
Upload upload=post.getValue(Upload.class);
mupload.add(upload);
}
customQuoteAdapter=new CustomQuoteAdapter( Images.this,
mupload);
recyclerView.setAdapter(customQuoteAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getApplicationContext(),
"ERROR"+databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});

You have a bussiness (sic) level in your JSON, that you're not handling in your code. The simplest way to fix this is to attach your listener to that bussiness node:
databaseReference=firebaseDatabase.getInstance().getReference("Catagories/Bussiness");
mupload=new ArrayList<>();`
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot post : dataSnapshot.getChildren()) {
Upload upload=post.getValue(Upload.class);
mupload.add(upload);
}
customQuoteAdapter=new CustomQuoteAdapter( Images.this, mupload);
recyclerView.setAdapter(customQuoteAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getApplicationContext(), "ERROR"+databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
If you want to get all URLS for all nodes under Categories, you'll need to add a loop inside onDataChange. Something like:
databaseReference=firebaseDatabase.getInstance().getReference("Catagories");
mupload=new ArrayList<>();`
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot categorySnapshot : dataSnapshot.getChildren()) {
for(DataSnapshot linkSnapshot : categorySnapshot.getChildren()) {
Upload upload=linkSnapshot.getValue(Upload.class);
mupload.add(upload);
}
}
customQuoteAdapter=new CustomQuoteAdapter( Images.this, mupload);
recyclerView.setAdapter(customQuoteAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getApplicationContext(), "ERROR"+databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});

Should it be?
public String getImageUrl() {
return this.imageUrl;
}