Realtime_FireBase Data Insertion and Retrieve

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<layout
    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"
    >




    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <EditText
            android:id="@+id/editTextName"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:layout_marginTop="250dp"
            android:hint="Enter your name"
            android:textStyle="bold"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/buttonSend"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Send Data"
            app:layout_constraintTop_toBottomOf="@+id/editTextName"
            android:layout_marginTop="20dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"/>

        <TextView
            android:id="@+id/textViewName"
            android:layout_width="300dp"
            android:layout_height="30dp"
            android:gravity="center"
            android:text="TextView"
            android:textStyle="bold"
            android:layout_marginTop="20dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/buttonSend" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>

build.gradle

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
    id 'com.google.gms.google-services'



}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.example.realtime_firebase"
        minSdk 21
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'

    }
    buildFeatures {
        viewBinding = true
        dataBinding = true
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.4.2'
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'com.google.firebase:firebase-database:20.0.5'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation 'com.google.android.gms:play-services-location:20.0.0'


}

MainActivity.kt

package com.example.realtime_firebase

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import androidx.databinding.DataBindingUtil
import com.example.realtime_firebase.databinding.ActivityMainBinding
import com.google.firebase.database.*

class MainActivity : AppCompatActivity() {
    private lateinit var binding : ActivityMainBinding

//    var editTextName:EditText = EditText()
//    lateinit var buttonSend : Button

    val database : FirebaseDatabase = FirebaseDatabase.getInstance()

    //reach to the main database and add data
    val reference : DatabaseReference = database.reference.child("Users")
    val reference2 : DatabaseReference = database.reference

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

//        editTextName = findViewById(R.id.editTextName)
//        buttonSend = findViewById(R.id.buttonSend)
//        buttonSend.setOnClickListener {


        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.buttonSend.setOnClickListener {


            reference2.addValueEventListener(object : ValueEventListener{

                    override fun onDataChange(snapshot: DataSnapshot) {
                        val realName : String = snapshot.child("Users").child("name").value as String
                        binding.textViewName.text= realName
                    }
                    override fun onCancelled(error: DatabaseError) {
                        TODO("Not yet implemented")
                    }
                })


            //send the data to the database
            val userName: String = binding.editTextName.text.toString()
            reference.child("userName").setValue(userName)
            Toast.makeText(applicationContext,"Data enter successfully",Toast.LENGTH_SHORT).show()
        }

        }
    }

Q - If you want to show data in a toast that changes in database?
Ans -

Replace this onDataChange method from previous one in main Activity --

override fun onDataChange(snapshot: DataSnapshot) {
// val realName : String = snapshot.child("Users").child("name").value as String
// binding.textViewName.text= realName

                    val children = snapshot.children
                    
                       children.forEach {
                         Toast.makeText(applicationContext,it.toString(),Toast.LENGTH_LONG).show()
                    }
                }