Program to implement a Google sign-in in Xamarin

 Pre-requisites: Make sure you install Visual Studio 2022 Community Edition or an appropriate version 

1. You will need to create a project using Android app (Xamarin) template.

You can use the project name = TestMobileGDrive

                                            

2. Using References/Manage Nuget Packages, make sure you include following packages with appropriate version

Xamarin.AndroidX.AppCompat

Xamarin.Essentials

Xamarin.GooglePlayServices.Auth

Make sure your code is as follows

3. filename = activity_main.xml

project folder location = /Resources/layout (create this folder if need be and then add the xml file)

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

<RelativeLayout 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"

>

<TextView

android:text=""

android:textAppearance="?android:attr/textAppearanceMedium"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:id="@+id/account_name" />

<Button

android:id="@+id/sign_in_button"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/sign_in"

android:textColor="@android:color/white"

android:theme="@style/ThemeOverlay.MyDarkButton"

/>

</RelativeLayout>

4. Filename= strings.xml

Folder location: /values

Note: create the file and folder if necessary

Note: The google server client id given below is for example and will not work. Create your own OAuth client id as per the guide on https://developers.google.com/workspace/guides/create-credentials . Once created, replace it in the file within googleserverclientid tag. 

<resources>

<string name="app_name">TestMobileGDrive</string>

<string name="action_settings">Settings</string>

<!-- Button labels -->

<string name="sign_in">Sign In</string>

<string name="sign_out">Sign Out</string>

<string name="disconnect">Disconnect</string>

<string name="googleserverclientid">459354647154-d5beleb9ugbvnijq53dh9rf7i56mheta.apps.googleusercontent.com</string>

</resources>

5. Filename = styles.xml

Folder location:/ values

Note: create the file and folder if necessary

<resources>

<!-- Base application theme. -->

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

<!-- Customize your theme here. -->

<item name="colorPrimary">@color/colorPrimary</item>

<item name="colorPrimaryDark">@color/colorPrimaryDark</item>

<item name="colorAccent">@color/colorAccent</item>

</style>

<!-- Dark Buttons -->

<style name="ThemeOverlay.MyDarkButton" parent="ThemeOverlay.AppCompat.Dark">

<item name="colorButtonNormal">@color/blue_grey_500</item>

</style>

</resources>

6. Filename: colors.xml

Folder location: /values

Note: create the file and folder if necessary

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

<resources>

<!-- color name="colorPrimary">#2c3e50</color>

<color name="colorPrimaryDark">#1B3147</color>

<color name="colorAccent">#3498db</color -->

<color name="colorPrimary">#3F51B5</color>

<color name="colorPrimaryDark">#303F9F</color>

<color name="colorAccent">#FF4081</color>

<color name="launcher_background">#FFFFFF</color>

<color name="blue_grey_500">#607D8B</color>

<color name="blue_grey_600">#546E7A</color>

<color name="blue_grey_700">#455A64</color>

<color name="blue_grey_800">#37474F</color>

<color name="blue_grey_900">#263238</color>

</resources>

7. Filename: MainActivity.cs

Folder location: inside root project folder /

using Android.App;

using Android.Gms.Auth.Api.SignIn;

using Android.Gms.Common;

using Android.OS;

using Android.Runtime;

using Android.Widget;

using AndroidX.AppCompat.App;

using Android.Views;

using Android.Content;

using Android.Gms.Tasks;

using Android.Gms.Common.Apis;

using Android.Content.PM;

namespace TestMobileGDrive

{

[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true

, ConfigurationChanges = ConfigChanges.ScreenSize |

ConfigChanges.Orientation |

ConfigChanges.UiMode |

ConfigChanges.ScreenLayout |

ConfigChanges.SmallestScreenSize)

]

public class MainActivity : AppCompatActivity, View.IOnClickListener

{

public GoogleSignInClient mGoogleSignInClient;

const int RC_SIGN_IN = 9001;

protected override void OnCreate(Bundle savedInstanceState)

{

base.OnCreate(savedInstanceState);

Xamarin.Essentials.Platform.Init(this, savedInstanceState);

// Set our view from the "main" layout resource

SetContentView(Resource.Layout.activity_main);

RequestGoogleUserData();

}

public void OnClick(Android.Views.View v)

{

switch (v.Id)

{

case Resource.Id.sign_in_button:

signIn();

break;

// ...

}

}

private void signIn()

{

Intent signInIntent = mGoogleSignInClient.SignInIntent;

StartActivityForResult(signInIntent, RC_SIGN_IN);

}

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)

{

base.OnActivityResult(requestCode, resultCode, data);

if (requestCode == RC_SIGN_IN)

{

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

// a listener.

Task task = GoogleSignIn.GetSignedInAccountFromIntent(data);

HandleSignInResult(task);

}

}

protected override void OnStart()

{

base.OnStart();

// Check for existing Google Sign In account, if the user is already signed in

// the GoogleSignInAccount will be non-null.

GoogleSignInAccount account = GoogleSignIn.GetLastSignedInAccount(this);

// Set the dimensions of the Google sign-in button.

/*SignInButton signInButton = (SignInButton)FindViewById(Resource.Id.sign_in_button);

signInButton.SetSize(SignInButton.SizeStandard);

updateUI(account);*/

}

public void updateUI(GoogleSignInAccount account)

{

if (account == null)

{

//account is not signed in. make sign in button visible

FindViewById(Resource.Id.sign_in_button).Visibility = Android.Views.ViewStates.Visible;

}

else {

// account is signed in. make the signin button invisible

FindViewById(Resource.Id.sign_in_button).Visibility = Android.Views.ViewStates.Invisible;

//display account name

TextView accountName = (TextView)FindViewById(Resource.Id.account_name);

accountName.Text = account.Email + "\n Account token=" + account.IdToken;

}

}

public void RequestGoogleUserData()

{

// Configure sign-in to request the user's ID, email address, and basic

// profile. ID and basic profile are included in DEFAULT_SIGN_IN.

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

.RequestEmail()

.RequestIdToken(Resources.GetString(Resource.String.googleserverclientid))

.Build();

// Build a GoogleSignInClient with the options specified by gso.

mGoogleSignInClient = GoogleSignIn.GetClient(this, gso);

FindViewById(Resource.Id.sign_in_button).SetOnClickListener(this);

}

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)

{

Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

base.OnRequestPermissionsResult(requestCode, permissions, grantResults);

}

private void HandleSignInResult(Task completedTask)

{

try

{

ApiException apiEx = new ApiException(Statuses.ResultSuccess);

GoogleSignInAccount account =

(GoogleSignInAccount) completedTask.GetResult(apiEx.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.

string err = "signInResult:failed code=" + e.StatusCode;

updateUI(null);

}

}

}

}