I have an Android Studio project where I am making a school-project Android app which transfers files between two devices, and while moving some methods and variables from my ChooseFile.java to my TransferFragment.java (i also changed the fragment’s xml layout file with the right context) all seemed to go well, until I encountered this error after launching my app once on an emulator device and opening the Transfer Fragment:
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

Now the strange thing is it only happens from time to time only when I open this fragment. I have attached the TransferFragment.java code below, I tried removing everything inside the onCreateView method (except for the rootview of course) and the app would still crash from time to time with the same error message.

TransferFragment.java:

package com.example.myproject;

import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.OnProgressListener;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;

import java.util.Calendar;
import java.util.Date;

public class TransferFragment extends Fragment implements View.OnClickListener {
    Dialog d;
    TextView btnOk, btnSettings;
    LinearLayout wifi_direct, nfc;
    private DataPassListener mListener;
    EditText name, receiver;
    TextView upload;
    ImageView add, iv_img;
    StorageReference storageReference;
    DatabaseReference databaseReference;
    int SELECT_PICTURE = 200;
    Uri image;
    Intent intent;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_transfer, container, false);
        passData("transfer");
        databaseReference = FirebaseDatabase.getInstance().getReference("Uploads");
        storageReference = FirebaseStorage.getInstance().getReference();
        name = (rootView).findViewById(R.id.name);
        receiver = (rootView).findViewById(R.id.receiver);
        iv_img = (rootView).findViewById(R.id.image);
        upload = (rootView).findViewById(R.id.upload);
        upload.setOnClickListener(this);
        add = (rootView).findViewById(R.id.add);
        add.setOnClickListener(this);
        intent = new Intent(getActivity(), MainScreen.class);
        return rootView;
    }

    @Override
    public void onClick(View v) {
        if(v==btnOk)
        {
            d.dismiss();
        }
        if(v==btnSettings)
        {
            startActivityForResult(new Intent(android.provider.Settings.ACTION_SETTINGS), 0);
            d.dismiss();
        }
        if(v==wifi_direct)
        {
            Intent intent = new Intent(getActivity(), ChooseFile.class);
            startActivity(intent);
            intent.putExtra("mode", "wifi");
        }
        if(v==nfc)
        {
            Intent intent = new Intent(getActivity(), ChooseFile.class);
            startActivity(intent);
            intent.putExtra("mode", "nfc");
        }
        if(v==add)
        {
            selectFiles();
        }
        if(v==upload)
        {
            uploadFiles(image);
        }

    }
    public interface DataPassListener {
        void onDataPass(String data);
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        try {
            mListener = (DataPassListener) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString() + " must implement DataPassListener");
        }
    }

    public void passData(String data) {
        if (mListener != null) {
            mListener.onDataPass(data);
        }
    }
    public void selectFiles() {
        Intent intent = new Intent();
        intent.setType("*/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent, "Select files:"), SELECT_PICTURE);
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==SELECT_PICTURE && resultCode==-1 && data!=null && data.getData()!=null)
        {
            image = data.getData();
            iv_img.setImageURI(image);
        }
        else
        {
            Log.e("ChooseFile", "Invalid file selection data");
        }
    }
    public void uploadFiles(Uri data) {
        final ProgressDialog progressDialog = new ProgressDialog(getActivity());
        progressDialog.setTitle("Uploading...");
        progressDialog.show();
        StorageReference reference = storageReference.child("Uploads/"+String.valueOf(name.getText()));
        if(data!=null)
        {
            reference.putFile(data).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                @Override
                public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                    Task<Uri> uriTask = taskSnapshot.getStorage().getDownloadUrl();
                    uriTask.addOnCompleteListener(new OnCompleteListener<Uri>() {
                        @Override
                        public void onComplete(@NonNull Task<Uri> task) {
                            if (task.isSuccessful()) {
                                Uri url = task.getResult();
                                Date currentTime = Calendar.getInstance().getTime();
                                FirebaseAuth mAuth = FirebaseAuth.getInstance();
                                FirebaseUser currentUser = mAuth.getCurrentUser();
                                Transfer transfer = new Transfer(String.valueOf(name.getText()), currentTime, currentUser.getDisplayName(), url.toString(), String.valueOf(receiver.getText()), true);
                                databaseReference.child(transfer.getName()).setValue(transfer);
                                progressDialog.dismiss();
                            } else {
                            }
                        }
                    });
                }
            }).addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
                @Override
                public void onProgress(@NonNull UploadTask.TaskSnapshot snapshot) {
                    double progress = (100.0*snapshot.getBytesTransferred())/snapshot.getTotalByteCount();
                    progressDialog.setMessage("Uploaded "+(int)progress+"%");
                }
            });
        }
    }
}

I have never encountered something like this, and while it is not critical for my project I would still love to hear any opinions from much more experienced people who might know what could be the cause for this.

In case it matters, the Fragment is opened inside of another activity and is contained within a FrameLayout in said activity, here is the code which opens it

getSupportFragmentManager().beginTransaction().replace(R.id.container, new TransferFragment())
                    .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE).commit();

Sorry in advance for my messy code.