phone authentication in android using Firebase

Step 1:   Add Firebase to your Android project

Step 2: Add this line build.Gradle(project)

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:4.1.1"
        classpath 'com.google.gms:google-services:4.3.5'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Step 3: Add this dependency build.Gradle (app level)

plugins {
    id 'com.android.application'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.ruhul.firebasephoneauth"
        minSdkVersion 16
        targetSdkVersion 30
        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
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'

    implementation platform('com.google.firebase:firebase-bom:27.1.0')
    implementation 'com.google.firebase:firebase-analytics'
    
    //firebase phonnumber auth andriod
    implementation 'com.firebaseui:firebase-ui-auth:7.1.1'
}
apply plugin: 'com.google.gms.google-services'

Step 4: Add style  LogingTheme themes.xml:   res/values/themes/themes.xml 

<style name="LoginTheme" parent="FirebaseUI">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    <item name="colorButtonNormal">@color/colorAccent</item>
    <item name="colorControlNormal">@android:color/white</item>
    <item name="colorControlActivated">@android:color/black</item>
    <item name="colorControlHighlight">@android:color/black</item>
    <item name="android:textColor">@android:color/black</item>
    <item name="android:textColorPrimary">@android:color/black</item>
    <item name="android:textColorSecondary">@android:color/black</item>
    <item name="android:windowBackground">@drawable/background</item>
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="android:textColorHint">@android:color/black</item>
    <item name="android:windowFullscreen">true</item>

</style>

Step 5: After that create signin_layout.xml:   res/layout/signin_layout.xml 

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="@drawable/rid_bg"
    android:layout_height="match_parent">

    <com.google.android.material.button.MaterialButton
        android:id="@+id/phone_login_id"
        android:drawableLeft="@drawable/fui_ic_phone_white_24dp"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="150dp"
        android:layout_marginLeft="15dp"
        android:layout_marginRight="15dp"
        android:text="sign in Phone"
        android:backgroundTint="#00796B"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        
    </com.google.android.material.button.MaterialButton>

</RelativeLayout>

Step 6: After that, you can now full code check 

package com.ruhul.firebasephoneauth;

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

import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

import com.firebase.ui.auth.AuthMethodPickerLayout;
import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.auth.IdpResponse;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

import java.util.Arrays;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private List<AuthUI.IdpConfig> idpConfigList;

    private int loging_request_code=1;

    private FirebaseAuth mauth;
    private FirebaseUser user;
    private FirebaseAuth.AuthStateListener authStateListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        idpConfigList= Arrays.asList(

                new AuthUI.IdpConfig.PhoneBuilder().build()
        );

        mauth=FirebaseAuth.getInstance();

        authStateListener=new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {

                user=firebaseAuth.getCurrentUser();
                if (user!=null)
                {
                    gotohome();

                }
                else {
                    // user phone number not authentication
                    need_login();
                }
            }
        };
    }

    private void need_login() {

        AuthMethodPickerLayout authMethodPickerLayout=new AuthMethodPickerLayout
                .Builder(R.layout.singin_layout)
                .setPhoneButtonId(R.id.phone_login_id)
                .build();


        startActivityForResult(
                AuthUI.getInstance()
                        .createSignInIntentBuilder()
                        .setAuthMethodPickerLayout(authMethodPickerLayout)
                        .setIsSmartLockEnabled(false)
                        .setTheme(R.style.LoginTheme)
                        .setAvailableProviders(idpConfigList)
                        .build(),
                loging_request_code);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    @Override
    protected void onStart() {
        super.onStart();
        mauth.addAuthStateListener(authStateListener);
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mauth!=null && authStateListener!=null)
        {
            mauth.removeAuthStateListener(authStateListener);
        }

    }

    private void gotohome() {

        startActivity(new Intent(MainActivity.this,HomeActivity.class));
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode==loging_request_code)
        {
            IdpResponse idpResponse=IdpResponse.fromResultIntent(data);
            if (resultCode==RESULT_OK)
            {
                Toast.makeText(this, "user authenticated", Toast.LENGTH_SHORT).show();

            }

        }
    }
}