Enabling Sign-in APi in Google Developer console

We need to enable Sign-in Api for our application in google developers console to use google sign-in  in our application.

1 . first we need to create a project in google developers console

    visit google developers  console 

     https://console.developers.google.com/project
2 . Click on create project button you will see the below screen

   

3 . Enter project name and click CREATE . Then we are directed to project home page  which will look like this

4 . Next we need to add Google API to our project. click on library on left menu and search for google api

5 . Configure  OAuth consent screen , click on 'OAuth consent screen'

 6 . Enter Application name and email id everything else is optional and click save

 7 . Configure Credentials 
      Google uses this to ensure that your application is not fake application . For the purpose of development we use debug certificate. When we deploy our app on play store we need real certificate, steps for geeting it is 
https://developer.android.com/tools/publishing/app-signing.html
we only need debug certificate for development , it is identified by SHA1 fingerprint 
Steps for getting SHA1
  I . SHA1 can be accesed from debug keystore
      on mac or linux it is in the ~/.android directory
      on windows it is in the c/user/<username>/.android directory
 II . Run the following  command
      on mac/linux open terminal 

keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android

      on windows 

keytool -list -v -keystore C:\Users\arun\.android\debug.keystore -alias androiddebugkey -storepass android

 III . you will get output like this 

  you can find SHA1 in the output

  If you are not getting output and getting the error in windows
 "keytool is not recognized as internal or external command "
  click on following link
  keytool is not recognized as internal or external commad
now we got our SHA1 , so we can configure credentials
8 . Click o credentials on the left side and you will be asked to create credentials

9 . Click on create credentials , now you will be asked to select a access method select OAuth client ID

10 . Next you will get a screen like this

11 . Select android and enter Name,Package name and SHA1. Package name should be same as your application package name

 12 . click on create and your client id will be ready

13 . now you can start coding for your application with google sign in.

click here for creating android  app with google sign-in
Google sign-in in android app