CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-databasenullpointerexception
markharrop
markharrop

Reputation: 876

correct way of deleting items from firebase

I'm trying to use removeValue() to remove items from my database. when i do my app crashes because there obviously becomes a null pointer in the onChange method.

What is the best way to remove Values from the database to stop my app from crashing?

these are the values I'm removing

 DatabaseReference detailref = bookingref.child("Bookings").child(customerid);
    detailref.child("Housenumber").removeValue();
    detailref.child("Address").removeValue();
    detailref.child("Postcode").removeValue();
    detailref.child("Phone").removeValue();
    detailref.child("Date").removeValue();

and in another activity, i call them using a value event Listener.

public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            if (dataSnapshot.getChildrenCount()!=0){
                house = dataSnapshot.child("Housenumber").getValue().toString();
                address = dataSnapshot.child("Address").getValue().toString();
                postcode = dataSnapshot.child("Postcode").getValue().toString();
                phone = dataSnapshot.child("Phone").getValue().toString();
                date = dataSnapshot.child("Date").getValue().toString();

here is the null pointer error from my Logcat

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
    at studios.p9p.h20.showroomfinish_adminapp.Booking_details$4.onDataChange

Upvotes: 0

Views: 243

Answers (2)

markharrop
markharrop

Reputation: 876

i used the answer above but in a much simpler way. i created a firebase model with all my strings in it called bookingModel() then in side my ondataChange() i could change all the bulky code below :)

house = dataSnapshot.child("Housenumber").getValue().toString();
address = dataSnapshot.child("Address").getValue().toString();
postcode = dataSnapshot.child("Postcode").getValue().toString();
phone = dataSnapshot.child("Phone").getValue().toString();
date = dataSnapshot.child("Date").getValue().toString();

id already got a userid string for the ref node called customerId so i used this instead in my onDataChanged()

if(dataSnapshot.hasChild(customerId))
bookingModel firebase_model = 
dataSnapshot.child(customerId).getValue(bookingModel.class)

then to delete i call

detailRef.child(customerId).removeValue();

Upvotes: 1

GusCorreia
GusCorreia

Reputation: 85

Could you please put more details of what are you trying to do? I think it's crashing because you're removing values separately. If you're trying to remove all the child data, you could try something like 

 DatabaseReference detailref = bookingref.child("Bookings").child(customerid);
 detailref.removeValue();

If not, maybe you could check if it exist before you try to get the values... Not the best or beautiful way to to it, but it may work...

public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
  if(dataSnapshot.exists()
     {
        if (dataSnapshot.getChildrenCount()!=0){
            if(dataSnapshot.hasChild("Housenumber")
           {
            house = dataSnapshot.child("Housenumber").getValue().toString();
            }
            if(dataSnapshot.hasChild("Address")
            {
            address = dataSnapshot.child("Address").getValue().toString();
            }
            if(dataSnapshot.hasChild("Postcode")
            {
            postcode = dataSnapshot.child("Postcode").getValue().toString();
            }
            if(dataSnapshot.hasChild("Phone")
            {
            phone = dataSnapshot.child("Phone").getValue().toString();
            }
            if(dataSnapshot.hasChild("Date")
            {
            date = dataSnapshot.child("Date").getValue().toString();
            }
     } }

Hope this helps :)

Upvotes: 2

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