Android Java Project to Integrate Google OAuth2 Login & Logout System & Save User Info in SharedPreferences

Welcome folks today in this blog post we will be seeing how to integrate google oauth2 login and logout system and save user info in SharedPreferences in java. All the full source code of the application is shown below.

Get Started

In order to get started you need to make a new android project inside the android studio and then you will see the below directory structure as shown below at the end of the project.

Now first of all you need to go to build.gradle file and copy paste the below dependencies as shown below

build.gradle

dependencies {

    implementation 'com.google.android.gms:play-services-auth:19.2.0'
    implementation 'com.github.bumptech.glide:glide:4.12.0'

}

dependencies {

implementation 'com.google.android.gms:play-services-auth:19.2.0'

implementation 'com.github.bumptech.glide:glide:4.12.0'

}

Now we need to edit the AndroidManifest.xml file and add the necessary internet permission as shown below

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/Theme.Imagetopdf"
        tools:targetApi="31">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

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

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools">

<uses-permission android:name="android.permission.INTERNET"/>

<application

android:allowBackup="true"

android:dataExtractionRules="@xml/data_extraction_rules"

android:fullBackupContent="@xml/backup_rules"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:supportsRtl="true"

android:theme="@style/Theme.Imagetopdf"

tools:targetApi="31">

<activity

android:name=".MainActivity"

android:exported="true">

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

Editing the Main Layout

Now we need to edit the activity_main.xml file for the project where we will have the simple Button widget as shown below to allow the user to sign in with google using oauth2 as shown below.

activity_main.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">

    <Button
        android:id="@+id/btn_sign_in"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Sign in with Google"
        android:layout_centerInParent="true"/>


</RelativeLayout>

<?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">

<Button

android:id="@+id/btn_sign_in"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Sign in with Google"

android:layout_centerInParent="true"/>

</RelativeLayout>

And now we need to edit the MainActivity.java file and copy paste the following code

MainActivity.java

package com.example.googleoauth2;


import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.common.api.ApiException;
import com.google.android.gms.tasks.Task;

public class MainActivity extends AppCompatActivity {


    private static final int RC_SIGN_IN = 1;
    private static final String TAG = "GoogleActivity";
    private GoogleSignInClient mGoogleSignInClient;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      
        Button signInButton = findViewById(R.id.btn_sign_in);
        signInButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                signIn();
            }
        });


        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .build();

        mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
    }

    private void signIn() {
        Intent signInIntent = mGoogleSignInClient.getSignInIntent();
        startActivityForResult(signInIntent, RC_SIGN_IN);
    }
}

package com.example.googleoauth2;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import com.google.android.gms.auth.api.signin.GoogleSignIn;

import com.google.android.gms.auth.api.signin.GoogleSignInAccount;

import com.google.android.gms.auth.api.signin.GoogleSignInClient;

import com.google.android.gms.auth.api.signin.GoogleSignInOptions;

import com.google.android.gms.common.api.ApiException;

import com.google.android.gms.tasks.Task;

public class MainActivity extends AppCompatActivity {

private static final int RC_SIGN_IN = 1;

private static final String TAG = "GoogleActivity";

private GoogleSignInClient mGoogleSignInClient;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button signInButton = findViewById(R.id.btn_sign_in);

signInButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

signIn();

}

});

GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)

.requestEmail()

.build();

mGoogleSignInClient = GoogleSignIn.getClient(this, gso);

}

private void signIn() {

Intent signInIntent = mGoogleSignInClient.getSignInIntent();

startActivityForResult(signInIntent, RC_SIGN_IN);

}

As you can see we are getting the reference of the Sign In button and then we are initializing the onClick listener to the button and here we are declaring the GoogleSignOptions client of the google oauth2 login where we are requesting the profile details of the user such as the display name,email and the profile picture of the user. And now we are using the Intent class to open the account picker window as shown below

Now after user selects his or her account now we need to implement the onActivityResult() method as shown below

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

        // Result returned from launching the Intent from GoogleSignInClient.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            // The Task returned from this call is always completed, no need to attach
            // a listener.
            Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
            handleSignInResult(task);
        }
    }

@Override

public void onActivityResult(int requestCode, int resultCode, Intent data) {

super.onActivityResult(requestCode, resultCode, data);

// Result returned from launching the Intent from GoogleSignInClient.getSignInIntent(...);

if (requestCode == RC_SIGN_IN) {

// The Task returned from this call is always completed, no need to attach

// a listener.

Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);

handleSignInResult(task);

}

As you can see in the above java code we are checking if the user has selected a valid account and then we are calling the handleSignInResult() method where we are passing the data of the signed account. Now we need to write that method

  private void handleSignInResult(Task<GoogleSignInAccount> completedTask) {
        try {
            GoogleSignInAccount account = completedTask.getResult(ApiException.class);
            // Signed in successfully, show authenticated UI.
            updateUI(account);
        } catch (ApiException e) {
            // The ApiException status code indicates the detailed failure reason.
            // Please refer to the GoogleSignInStatusCodes class reference for more information.
            Log.w(TAG, "signInResult:failed code=" + e.getStatusCode());
            updateUI(null);
        }
    }

private void handleSignInResult(Task<GoogleSignInAccount> completedTask) {

try {

GoogleSignInAccount account = completedTask.getResult(ApiException.class);

// Signed in successfully, show authenticated UI.

updateUI(account);

} catch (ApiException e) {

// The ApiException status code indicates the detailed failure reason.

// Please refer to the GoogleSignInStatusCodes class reference for more information.

Log.w(TAG, "signInResult:failed code=" + e.getStatusCode());

updateUI(null);

}

As you can see we are getting the result of the successfully signIn and then now we need to update the user interface in this case we need to fetch the user details and display it inside the userdetails activity. Now we are calling the updateUI() method. Now we need to define this method as shown below

private void updateUI(GoogleSignInAccount account) {
        if (account != null) {
            String email = account.getEmail();
            String name = account.getDisplayName();
            String picture = String.valueOf(account.getPhotoUrl());

            Intent intent = new Intent(this, UserDetailsActivity.class);
            intent.putExtra("email", email);
            intent.putExtra("name", name);
            intent.putExtra("picture",picture);
            startActivity(intent);
        } else {

        }
    }

private void updateUI(GoogleSignInAccount account) {

if (account != null) {

String email = account.getEmail();

String name = account.getDisplayName();

String picture = String.valueOf(account.getPhotoUrl());

Intent intent = new Intent(this, UserDetailsActivity.class);

intent.putExtra("email", email);

intent.putExtra("name", name);

intent.putExtra("picture",picture);

startActivity(intent);

} else {

}

As you can see we are getting the account details such as the displayName,email and the picture of the user. And now we are navigating to the UserDetails activity and passing this user data using the putExtra() method. And then we are calling the startActivity() method to navigate to that activity.

Now we need to create a empty activity called UserDetailsActivity.java and also we need to copy paste the below xml code for the layout of this activity as shown below

activity_user_details.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">

    <ImageView
        android:id="@+id/iv_profile"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center_horizontal"
        android:scaleType="centerCrop"
        android:layout_marginBottom="16dp"/>

    <TextView
        android:id="@+id/tv_email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:layout_gravity="center_horizontal"/>

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="16dp"/>


    <Button
        android:id="@+id/logout_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Logout"
        android:layout_gravity="center" />

</LinearLayout>

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:padding="16dp">

<ImageView

android:id="@+id/iv_profile"

android:layout_width="100dp"

android:layout_height="100dp"

android:layout_gravity="center_horizontal"

android:scaleType="centerCrop"

android:layout_marginBottom="16dp"/>

<TextView

android:id="@+id/tv_email"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="18sp"

android:layout_gravity="center_horizontal"/>

<TextView

android:id="@+id/tv_name"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="18sp"

android:layout_gravity="center_horizontal"

android:layout_marginTop="16dp"/>

<Button

android:id="@+id/logout_button"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Logout"

android:layout_gravity="center" />

</LinearLayout>

As you can see we have the ImageView widget where we are display the profile picture of the user and then we have two TextView widgets where we display the display name and the email of the user and then we have the logout button to sign out from the google account.

Now we need to copy paste the below java code inside the UserDetailsActivity.java as shown below

UserDetailsActivity.java

package com.example.googleoauth2;

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

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;

public class UserDetailsActivity extends AppCompatActivity {

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

        Intent intent = getIntent();
        String email = intent.getStringExtra("email");
        String name = intent.getStringExtra("name");
        String profilePictureUrl = intent.getStringExtra("picture");

        ImageView ivProfile = findViewById(R.id.iv_profile);
        Glide.with(this)
                .load(profilePictureUrl)
                .circleCrop()
                .into(ivProfile);

        TextView tvEmail = findViewById(R.id.tv_email);
        tvEmail.setText("Email: " + email);

        TextView tvName = findViewById(R.id.tv_name);
        tvName.setText("Name: " + name);
    }
}

package com.example.googleoauth2;

import androidx.annotation.NonNull;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.TextView;

import com.bumptech.glide.Glide;

import com.google.android.gms.auth.api.signin.GoogleSignIn;

import com.google.android.gms.auth.api.signin.GoogleSignInClient;

import com.google.android.gms.auth.api.signin.GoogleSignInOptions;

import com.google.android.gms.tasks.OnCompleteListener;

import com.google.android.gms.tasks.Task;

public class UserDetailsActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_user_details);

Intent intent = getIntent();

String email = intent.getStringExtra("email");

String name = intent.getStringExtra("name");

String profilePictureUrl = intent.getStringExtra("picture");

ImageView ivProfile = findViewById(R.id.iv_profile);

Glide.with(this)

.load(profilePictureUrl)

.circleCrop()

.into(ivProfile);

TextView tvEmail = findViewById(R.id.tv_email);

tvEmail.setText("Email: " + email);

TextView tvName = findViewById(R.id.tv_name);

tvName.setText("Name: " + name);

}

As you can see we are getting the passed user info data from the intent and then we are displaying the profile pic url and are loading it inside the imageView using the Glide library. And also we are displaying the display name and email of the user as shown below

Integrating Logout Method

Now guys we will allow the users to logout from the google account once they press the signout button inside the app. For that you need to add the below java code inside the UserDetailsActivity.java file as shown below

package com.example.googleoauth2;

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

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;

public class UserDetailsActivity extends AppCompatActivity {

    private GoogleSignInClient mGoogleSignInClient;


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

        mGoogleSignInClient = GoogleSignIn.getClient(this,
                new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).build());

        Intent intent = getIntent();
        String email = intent.getStringExtra("email");
        String name = intent.getStringExtra("name");
        String profilePictureUrl = intent.getStringExtra("picture");

        ImageView ivProfile = findViewById(R.id.iv_profile);
        Glide.with(this)
                .load(profilePictureUrl)
                .circleCrop()
                .into(ivProfile);

        TextView tvEmail = findViewById(R.id.tv_email);
        tvEmail.setText("Email: " + email);

        TextView tvName = findViewById(R.id.tv_name);
        tvName.setText("Name: " + name);

        Button logoutButton = findViewById(R.id.logout_button);
        logoutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Sign out of Google account
                mGoogleSignInClient.signOut().addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                 
                        // Return to MainActivity
                        Intent intent = new Intent(UserDetailsActivity.this, MainActivity.class);
                        startActivity(intent);
                        finish();
                    }
                });
            }
        });
    }
}

package com.example.googleoauth2;

import androidx.annotation.NonNull;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.TextView;

import com.bumptech.glide.Glide;

import com.google.android.gms.auth.api.signin.GoogleSignIn;

import com.google.android.gms.auth.api.signin.GoogleSignInClient;

import com.google.android.gms.auth.api.signin.GoogleSignInOptions;

import com.google.android.gms.tasks.OnCompleteListener;

import com.google.android.gms.tasks.Task;

public class UserDetailsActivity extends AppCompatActivity {

private GoogleSignInClient mGoogleSignInClient;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_user_details);

mGoogleSignInClient = GoogleSignIn.getClient(this,

new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).build());

Intent intent = getIntent();

String email = intent.getStringExtra("email");

String name = intent.getStringExtra("name");

String profilePictureUrl = intent.getStringExtra("picture");

ImageView ivProfile = findViewById(R.id.iv_profile);

Glide.with(this)

.load(profilePictureUrl)

.circleCrop()

.into(ivProfile);

TextView tvEmail = findViewById(R.id.tv_email);

tvEmail.setText("Email: " + email);

TextView tvName = findViewById(R.id.tv_name);

tvName.setText("Name: " + name);

Button logoutButton = findViewById(R.id.logout_button);

logoutButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

// Sign out of Google account

mGoogleSignInClient.signOut().addOnCompleteListener(new OnCompleteListener<Void>() {

@Override

public void onComplete(@NonNull Task<Void> task) {

// Return to MainActivity

Intent intent = new Intent(UserDetailsActivity.this, MainActivity.class);

startActivity(intent);

finish();

}

});

}

});

}

As you can see we have added the onClick listener to the signout button and inside it we are calling the signOut() which is provided by the library and then we are navigating back to the MainActivity using the Intent class

Saving User Data in SharedPreferences

Now guys we will be see how we can save user data so that when user closes or restarts the app the user should be redirected to the UserDetails activity if they are already logged in. For this you need to add the below code inside the MainActivity.java file as shown below

MainActivity.java

private void updateUI(GoogleSignInAccount account) {
        if (account != null) {
            String email = account.getEmail();
            String name = account.getDisplayName();
            String picture = String.valueOf(account.getPhotoUrl());

            SharedPreferences.Editor editor = getSharedPreferences("userdata", MODE_PRIVATE).edit();
            editor.putString("name",account.getDisplayName());
            editor.putString("email", account.getEmail());
            editor.putString("picture", account.getPhotoUrl() != null ? account.getPhotoUrl().toString() : null);
            editor.apply();

            Intent intent = new Intent(this, UserDetailsActivity.class);
            intent.putExtra("email", email);
            intent.putExtra("name", name);
            intent.putExtra("picture",picture);
            startActivity(intent);
        } else {

        }
    }

private void updateUI(GoogleSignInAccount account) {

if (account != null) {

String email = account.getEmail();

String name = account.getDisplayName();

String picture = String.valueOf(account.getPhotoUrl());

SharedPreferences.Editor editor = getSharedPreferences("userdata", MODE_PRIVATE).edit();

editor.putString("name",account.getDisplayName());

editor.putString("email", account.getEmail());

editor.putString("picture", account.getPhotoUrl() != null ? account.getPhotoUrl().toString() : null);

editor.apply();

Intent intent = new Intent(this, UserDetailsActivity.class);

intent.putExtra("email", email);

intent.putExtra("name", name);

intent.putExtra("picture",picture);

startActivity(intent);

} else {

}

Here inside the updateUI() method we just need to add the above code to save the user details inside the SharedPreferences once they are successfully logged in. And then also we need to add the below lines of code inside the onCreate() method to check if they are logged in or not. If they are logged in then we will be redirecting to UserDetails Activity as shown below

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

        SharedPreferences prefs = getSharedPreferences("userdata", MODE_PRIVATE);
        String accountName = prefs.getString("name", null);
        String email = prefs.getString("email",null);
        String profilePictureUrl = prefs.getString("picture", null);

        if(accountName != null){
            Intent intent = new Intent(MainActivity.this, UserDetailsActivity.class);
            intent.putExtra("email", email);
            intent.putExtra("name", accountName);
            intent.putExtra("picture", profilePictureUrl);
            startActivity(intent);
        }


        Button signInButton = findViewById(R.id.btn_sign_in);
        signInButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                signIn();
            }
        });


        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .build();

        mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
    }

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

SharedPreferences prefs = getSharedPreferences("userdata", MODE_PRIVATE);

String accountName = prefs.getString("name", null);

String email = prefs.getString("email",null);

String profilePictureUrl = prefs.getString("picture", null);

if(accountName != null){

Intent intent = new Intent(MainActivity.this, UserDetailsActivity.class);

intent.putExtra("email", email);

intent.putExtra("name", accountName);

intent.putExtra("picture", profilePictureUrl);

startActivity(intent);

}

Button signInButton = findViewById(R.id.btn_sign_in);

signInButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

signIn();

}

});

GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)

.requestEmail()

.build();

mGoogleSignInClient = GoogleSignIn.getClient(this, gso);

}

As you can see in the above java code we are reading or getting the stored user details from the SharedPreferences and then we are redirecting the user to the UserDetails Activity if they are already logged in.

Now also we need to clear or delete the data inside the SharedPreferences once we signout . So inside the UserDetailsActivity.java file we need to add some code as shown below

UserDetailsActivity.java

 Button logoutButton = findViewById(R.id.logout_button);
        logoutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Sign out of Google account
                mGoogleSignInClient.signOut().addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        // Clear login info from SharedPreferences
                        SharedPreferences.Editor editor = getSharedPreferences("userdata", MODE_PRIVATE).edit();
                        editor.clear();
                        editor.apply();

                        // Return to MainActivity
                        Intent intent = new Intent(UserDetailsActivity.this, MainActivity.class);
                        startActivity(intent);
                        finish();
                    }
                });
            }
        });

Button logoutButton = findViewById(R.id.logout_button);

logoutButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

// Sign out of Google account

mGoogleSignInClient.signOut().addOnCompleteListener(new OnCompleteListener<Void>() {

@Override

public void onComplete(@NonNull Task<Void> task) {

// Clear login info from SharedPreferences

SharedPreferences.Editor editor = getSharedPreferences("userdata", MODE_PRIVATE).edit();

editor.clear();

editor.apply();

// Return to MainActivity

Intent intent = new Intent(UserDetailsActivity.this, MainActivity.class);

startActivity(intent);

finish();

}

});

}

});

As you can see inside the above logout function we are simply clearing the data present inside the SharedPreferences by using the clear() method.