Cant find the reason for sudden null pointer exception in real time database Firebase

Question

I have this weird issue with Firebase. I am trying to retrieve the database in EditText so that i can update them but sometimes it retrieves them perfectly and sometimes suddenly gives a NullPointerException.

My Real Time Database:

Mobile->
Apple->
    Iphone 13->
        Display:"4K"
        Processor:"A16"
        Ram:"12GB"
    Iphone 14-> 
        Display:"4K"
        Processor:"A16"
        Ram:"12 GB"
   One Plus->
    One Plus 10->
        Display:"2K"
        Processor:"Snapdraggon895+"
        Ram:"16 GB"
    One Plus 11->
        Display:"4K"
        Processor:"Snapdraggon 950"
        Ram:"16 GB"

My Update Activity:

<code>
     package com.example.firebasepractice;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

     public class UpdateDBActivity extends AppCompatActivity {

         FirebaseDatabase firebaseDatabase;
         EditText updateCompany, updateDevice, updateDisplay, updateProcessor, updateRam;
         List<AppModelClass> myList;
         AppModelClass model;

              @Override
         protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update);
        updateCompany = findViewById(R.id.updateCompany);
        updateDevice = findViewById(R.id.updateDevice);
        updateDisplay = findViewById(R.id.updateDisplay);
        updateProcessor = findViewById(R.id.updateProcessor);
        updateRam = findViewById(R.id.updateRam);
        model = new AppModelClass();
        myList = new ArrayList<>();
    }

    public void getData(View view) {
        String textCompany = updateCompany.getText().toString();
        String textDevice = updateDevice.getText().toString();
        DatabaseReference ref = FirebaseDatabase
                .getInstance("https://fir-practice-4dc05-default-rtdb.asia-southeast1.firebasedatabase.app/")
                .getReference()
                .child("Mobile")
                .child(textCompany)
                .child(textDevice);
        ref.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                AppModelClass app = snapshot.getValue(AppModelClass.class);
                updateProcessor.setText(app.getProcessor());
                updateDisplay.setText(app.getDisplay());
                updateRam.setText(app.getRam());
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });

    }

    public void updateDB(View view) {
        String textDisplay = updateDisplay.getText().toString();
        String textProcessor = updateProcessor.getText().toString();
        String textRam = updateRam.getText().toString();
        String textCompany = updateCompany.getText().toString();
        String textDevice = updateDevice.getText().toString();
        if (textDisplay.isEmpty() || textDevice.isEmpty() || textCompany.isEmpty()
                || textRam.isEmpty() || textProcessor.isEmpty()) {
            Toast.makeText(this, "Please fill all details", Toast.LENGTH_SHORT).show();
        } else {
            HashMap<String, Object> myMap = new HashMap<>();
            myMap.put("Display", textDisplay);
            myMap.put("Processor", textProcessor);
            myMap.put("Ram", textRam);
            FirebaseDatabase
                    .getInstance("https://fir-practice-4dc05-default-rtdb.asia-southeast1.firebasedatabase.app/")
                    .getReference("Mobile")
                    .child(textCompany)
                    .child(textDevice)
                    .setValue(myMap).addOnSuccessListener(new OnSuccessListener<Void>() {
                        @Override
                        public void onSuccess(Void unused) {
                            Toast.makeText(UpdateDBActivity.this, "Database Updated", Toast.LENGTH_SHORT).show();
                            updateCompany.setText("");
                            updateDevice.setText("");
                            updateRam.setText("");
                            updateDisplay.setText("");
                            updateProcessor.setText("");
                        }
                    });

        }
    }
}
</code>

In the getData() method i try to retrieve the JSON through my AppModelClass (Model class/POJO Class) and sometimes i am successfully retrieving and sometimes i get a NullPointerException on my AppModelClass object (app) in onDataChanged() method. What am i doing wrong ?

This can be prevented with: `if (app != null) { ... }` - processor, display or RAM may also be `null`. The stack-trace should show exactly why it happens; the next time please provide that, too. — Martin Zeitler, May 29 '22 at 19:18
https://imgur.com/a/uQA4VMj This is the error message. I am trying to understand how come its null all of the sudden when it worked fine like 5 seconds ago. — peerzada burhan, May 30 '22 at 04:08

Cant find the reason for sudden null pointer exception in real time database Firebase

0 Answers0