Cloud FireStore

activity_note.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".NoteActivity">
    <EditText
        android:id="@+id/edit_title"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:layout_marginBottom="10dp"
        />
    <EditText
        android:id="@+id/edit_description"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:layout_marginBottom="10dp"
        />
    <Button android:id="@+id/btn_add"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="Add"
        android:onClick="addNote"
        />
    <ListView android:id="@+id/list_note"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />
</LinearLayout>

FirestoreActivity.java

package com.vokasi.firebaseb;

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

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

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.CollectionReference;
import com.google.firebase.firestore.DocumentReference;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;

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

import javax.annotation.Nullable;

public class FirestoreActivity extends AppCompatActivity {
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    CollectionReference note_ref = db.collection("notes");
    EditText edit_title;
    EditText edit_description;
    ListView list_note;
    ArrayList<Note> note_item = new ArrayList<>();
    NoteAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_firestore);
        edit_title = findViewById(R.id.edit_title);
        edit_description = findViewById(R.id.edit_description);
        list_note = findViewById(R.id.list_note);
    }

    @Override
    protected void onStart() {
        super.onStart();
        note_ref.addSnapshotListener(this, new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {
                if (e != null){
                    return;
            }
                note_item.clear();
                for(QueryDocumentSnapshot documentSnapshot: queryDocumentSnapshots){
                    Note note = documentSnapshot.toObject(Note.class);
                    note.setDocId(documentSnapshot.getId());
                    note_item.add(note);
                }

                adapter = new NoteAdapter(FirestoreActivity.this,note_item);
                adapter.notifyDataSetChanged();
                list_note.setAdapter(adapter);
            }
        });
    }

    public void addNote(View view){
        String title = edit_title.getText().toString();
        String description = edit_description.getText().toString();

        Map<String, Object> user = new HashMap<>();
        user.put("title", title);
        user.put("description", description);

        note_ref.add(user)
                .addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
                    @Override
                    public void onSuccess(DocumentReference documentReference) {
                        edit_title.setText(null);
                        edit_description.setText(null);
                        Toast.makeText(FirestoreActivity.this, "Success", Toast.LENGTH_LONG).show();
                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Toast.makeText(FirestoreActivity.this, "Error"+e, Toast.LENGTH_LONG).show();
                    }
                });
    }
}

list_note.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/note_id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView android:id="@+id/note_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@id/note_id"
        android:layout_alignParentRight="true"
        android:textAlignment="textEnd"
        />
    <TextView android:id="@+id/note_description"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/note_id"
        />
</RelativeLayout>

Note.java

package com.vokasi.firebase_a;

public class Note {
    String docId;
    String title;
    String description;

    public Note() {
    }

    public String getDocId() {
        return docId;
    }

    public void setDocId(String docId) {
        this.docId = docId;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

NoteActivity.java

package com.vokasi.firebase_a;

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

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

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.CollectionReference;
import com.google.firebase.firestore.DocumentReference;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;

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

import javax.annotation.Nullable;

public class NoteActivity extends AppCompatActivity {
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    CollectionReference note_ref = db.collection("notes");
    EditText edit_title;
    EditText edit_description;
    ListView list_note;
    List<String> note_item = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_note);

        edit_title = findViewById(R.id.edit_title);
        edit_description = findViewById(R.id.edit_description);
        list_note = findViewById(R.id.list_note);

    }

    @Override
    protected void onStart() {
        super.onStart();
        note_ref.addSnapshotListener(this, new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {
                if (e!=null){
                    return;
                }
                note_item.clear();
                String data="";

                for (QueryDocumentSnapshot documentSnapshot : queryDocumentSnapshots){
                    Note note = documentSnapshot.toObject(Note.class);
                    note.setDocId(documentSnapshot.getId());
                    String documentId = note.getDocId();
                    String title = note.getTitle();
                    String description = note.getDescription();

                    data += "ID: " + documentId
                            + "\nTitle: " + title + "\nDescription: " + description + "\n\n";
                    note_item.add(data);
                }
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_selectable_list_item,note_item);
                adapter.notifyDataSetChanged();
                list_note.setAdapter(adapter);

            }
        });
    }

    public void addNote(View view){
        String title = edit_title.getText().toString();
        String description = edit_description.getText().toString();

        Map<String,Object> note = new HashMap<>();
        note.put("title",title);
        note.put("description",description);

        db.collection("notes")
                .add(note)
                .addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
                    @Override
                    public void onSuccess(DocumentReference documentReference) {
                        edit_title.setText("");
                        edit_description.setText(null);
                        Toast.makeText(NoteActivity.this, "Success", Toast.LENGTH_LONG).show();
                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Toast.makeText(NoteActivity.this, "Error "+e, Toast.LENGTH_LONG).show();
                    }
                });
    }
}

NoteAdapter.java

package com.vokasi.firebaseb;

import android.app.Activity;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.util.ArrayList;

public class NoteAdapter extends ArrayAdapter<Note> {

    public NoteAdapter(Context context,ArrayList<Note> notes) {
        super(context, 0, notes);
    }

    public View getView(int position,View convertView, ViewGroup parent){
        if (convertView ==null){
            convertView =  ((Activity)getContext()).getLayoutInflater().inflate(R.layout.list_note,parent,false);
        }

        TextView note_id = (TextView) convertView.findViewById(R.id.note_id);
        TextView note_title = (TextView) convertView.findViewById(R.id.note_title);
        TextView note_description = (TextView) convertView.findViewById(R.id.note_description);

        Note note = getItem(position);
        note_id.setText(note.getDocId());
        note_title.setText(note.getTitle());
        note_description.setText(note.getDescription());
        return convertView;
    }
}