Release signed Android App,Google Plus Login and Google Map not Working

You have generate Sign keyHash like this .

keytool -exportcert -alias androiddebugkey -keystore %HOMEPATH%\.android\debug.keystore | openssl sha1 -binary | openssl
base64

For Example Like this

C:\Program Files\Java\jdk1.6.0_22\bin\keytool.exe" -exportcert -alias selvin -keystore c:\users\selvin\desktop\selvin.kp | C:\OpenSSL-Win32\bin\openssl sha1 -binary | C:\OpenSSL-Win32\bin\openssl base64

this is generate for CMD in your system add add this Hash key in your Google consol.

If you haven't yet added the release SHA1 to the firebase console or developer console, please do it first and make sure you add the google-services.json downloaded from the console to the root of the project folder as given in the previous answers. If the issue still persists even after doing this, please add the following line to the proguard-rules.pro of your project.

-keep class <package-name>.** {*;}

Note: This method may increase the size of your app-release.apk, but the oauth login will work for sure. To reduce the size, be particular about the class that you specify in the proguard. For example,

-keep class <package-name>.<class-name> {*;}

The class name can be found if you know which class the proguard compresses such that the class is not executed. In this case, it is the login oauth that may have been prevented by the proguard from being executed. So, add that class along with any other pojo classes associated with the login in the proguard as shown below:

-keep class <package-name>.<class-name> {*;}

-keep class <package-name>.<pojo-class> {*;} (if any)

Add all the classes associated with the login as shown and you will be good to go.