Google map is not appearing in android device -

Google map is not appearing in android device -

i working on google maps v2 android sdk version 19. included google-play-services_lib project. project working fine when updated google-play-services_lib project stopped working. there no error in project giving exception on runtime. updated version of google-play-service_lib 20.

secondly next https://developers.google.com/maps/documentation/android/start site here 2 line code:

<meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" />

i not understand should written in value field ?

android google-maps