LibraryFragment.java

package com.example.booksharing21;

import android.content.Context;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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 com.google.firebase.firestore.FirebaseFirestore;
import com.squareup.picasso.Picasso;

import java.util.ArrayList;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link LibraryFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class LibraryFragment extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;


    public LibraryFragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment LibraryFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static LibraryFragment newInstance(String param1, String param2) {
        LibraryFragment fragment = new LibraryFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
        onStart();
    }


    public ArrayList<info> infoList ;
    public HelperAdapter helperAdapter;
    public RecyclerView librec;
    public FirebaseDatabase mdb;


    public DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
    public String userid = FirebaseAuth.getInstance().getCurrentUser().getUid();
    public DatabaseReference db = FirebaseDatabase.getInstance().getReference("user-posts").child(userid);
    public Context mContext;
    public String key = mDatabase.child("user-posts/").push().getKey();

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_library, container, false);

        // Layout
        librec = view.findViewById(R.id.lib_re_view);
        LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
        librec.setLayoutManager(layoutManager);
        librec.setHasFixedSize(true);


        mDatabase = FirebaseDatabase.getInstance().getReference("user-posts").child(userid);



        // Array List
        infoList = new ArrayList<>();
        // Clear List

        ClearAll();

        // Getting Data from FDB
        GetDataFromFirebase();



        return view;

    }

    private void ClearAll() {
        if (infoList!=null){
            infoList.clear();

            if (helperAdapter != null){
                helperAdapter.notifyDataSetChanged();
            }
        }
        infoList = new ArrayList<>();

    }


    ValueEventListener listener;

    // selecting books from current user

    private void GetDataFromFirebase() {


        listener = new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {


                DatabaseReference db = FirebaseDatabase.getInstance().getReference("user-posts").child(userid);

                ClearAll();
                    for (DataSnapshot dataSnapshot : snapshot.getChildren()) {

                        info info = new info();

                        info.setPostid(dataSnapshot.child("postid").getValue().toString());
                        info.setUrl(dataSnapshot.child("url").getValue().toString());
                        info.setBookname(dataSnapshot.child("book name").getValue().toString());
                        info.setIsbn(dataSnapshot.child("isbn").getValue().toString());
                        info.setAuthor(dataSnapshot.child("author").getValue().toString());


                        infoList.add(info);

                    helperAdapter = new HelperAdapter(getContext(), infoList);
                    librec.setAdapter(helperAdapter);
                    helperAdapter.notifyDataSetChanged();

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

                Toast.makeText(getActivity(), "No books in your library", Toast.LENGTH_LONG).show();

            }

        };

        db.addListenerForSingleValueEvent(listener);
    };

    @Override
    public void onStart()
    {
        super.onStart();

        GetDataFromFirebase(); //onStart Called
    }


    public void onStop() {
        super.onStop();
        mDatabase.removeEventListener(listener);
    }

}