Android - Firebase Realtime Database with CRUD Operation

In this article, we will learn how to perform CRUD (Create, Read, Update, Delete) operations in android application based on Firebase Realtime Database. In this app, users can add an employee with their name and position to the database, fetch, update, and delete them.

I assume you know how to set up Firebase into Android project, so now, we will start implementing the layout and class.

Step 1: We design layout activity_main.xml with 2 edit texts and 2 buttons for submitting data and launch new activity for display data.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:padding="15dp"
    android:orientation="vertical">
    <ImageView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="fitXY"
        android:src="@drawable/download"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Name"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/edit_name"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Position"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/edit_position"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btn_submit"
        android:background="@android:color/holo_blue_dark"
        android:text="Submit"
        android:textColor="@android:color/white"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btn_open"
        android:text="Open" />
</LinearLayout>

implementation 'com.google.firebase:firebase-database:20.0.5'

After that you can click sync link on top right cornor to download dependency.

Step 3: Design model class for store data(tree node name in Firebase will have the same name) and display back

Employee.java

package com.hellokh.sovary.firetest;
import com.google.firebase.database.Exclude;
import java.io.Serializable;
public class Employee implements Serializable
{
    @Exclude
    private String key;
    private String name;
    private String position;
    public Employee(){}
    public Employee(String name, String position)
    {
        this.name = name;
        this.position = position;
    }
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name = name;
    }
    public String getPosition()
    {
        return position;
    }
    public void setPosition(String position)
    {
        this.position = position;
    }
    public String getKey()
    {
        return key;
    }
    public void setKey(String key)
    {
        this.key = key;
    }
}

DAOEmployee.java

package com.hellokh.sovary.firetest;
import com.google.android.gms.tasks.Task;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import java.util.HashMap;
public class DAOEmployee
{
    private DatabaseReference databaseReference;
    public DAOEmployee()
    {
        FirebaseDatabase db =FirebaseDatabase.getInstance();
        databaseReference = db.getReference(Employee.class.getSimpleName());
    }
     public Task<Void> add(Employee emp)
    {
        return databaseReference.push().setValue(emp);
    }
    public Task<Void> update(String key, HashMap<String ,Object> hashMap)
    {
        return databaseReference.child(key).updateChildren(hashMap);
    }
    public Task<Void> remove(String key)
    {
        return databaseReference.child(key).removeValue();
    }
    public Query get()
    {
        return databaseReference;
    }
}

We instance all database references in constructor once we instance the object DAO we can use the database reference at the same time. For those CRUD methods that have return value as Task<Void> we may easily implement in the future.

Step 5: Implement in MainActivity.java 

package com.hellokh.sovary.firetest;

import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.util.HashMap;
public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText edit_name = findViewById(R.id.edit_name);
        final EditText edit_position = findViewById(R.id.edit_position);
        Button btn_submit = findViewById(R.id.btn_submit);
        Button btn_open =findViewById(R.id.btn_open);
        btn_open.setOnClickListener(click ->
        {
            Intent intent = new Intent(MainActivity.this,RVActivity.class);
            startActivity(intent);
        });
        ///We pass data from other activity to edit
        Employee emp_edit = (Employee)getIntent().getSerializableExtra("EDIT");
        if(emp_edit !=null)
        {
            btn.setText("UPDATE");
            edit_name.setText(emp_edit.getName());
            edit_position.setText(emp_edit.getPosition());
            btn_open.setVisibility(View.GONE);
        }
        else
        {
            btn.setText("SUBMIT");
            btn_open.setVisibility(View.VISIBLE);
        }
        DAOEmployee dao =new DAOEmployee();
        btn_submit.setOnClickListener(v->
        {
            if(emp_edit==null)
            {
                Employee emp = new Employee(edit_name.getText().toString(), edit_position.getText().toString());
                //because add() method is return as Task so we can implement like if success we can perform other action and so on
                dao.add(emp).addOnSuccessListener(suc ->
                {
                    Toast.makeText(this, "Record is inserted", Toast.LENGTH_SHORT).show();
                }).addOnFailureListener(er ->
                {
                    Toast.makeText(this, "" + er.getMessage(), Toast.LENGTH_SHORT).show();
                });
            }
            else
            {
                HashMap<String, Object> hashMap = new HashMap<>();
                hashMap.put("name", edit_name.getText().toString());
                hashMap.put("position", edit_position.getText().toString());     
                //update is required key, this is manually input to update
                dao.update("-MXgqaKEPSYq9q8SQaVW", hashMap).addOnSuccessListener(suc ->
                {
                    Toast.makeText(this, "Record is updated", Toast.LENGTH_SHORT).show();
                    finish();
                }).addOnFailureListener(er ->
                {
                    Toast.makeText(this, "" + er.getMessage(), Toast.LENGTH_SHORT).show();
                });
            }
        });
    }
}

The video below is implemented Realtime Firebase from scratch

Download Project

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