02-17 18:16:09.870: E/GMPM(12680): GoogleService failed to initialize, status: 10, Missing an expected resource: 'R.string.google_app_id' for initializing Google services. Possible causes are missing google-services.json or com.google.gms.google-services gradle plugin.
I'm trying to remove this error log. I could find some advices about solving this kind of problems using google_play_services.json file like this link : GoogleService failed to initialize
But my project doesn't use gradle so I'll add google_app_id in my strings.xml. Now I'm confused. What exactly is google_app_id? Somebody says it's the project number, some says it's the project id... Even in google_play_services.json file there are some properties named "project_id", "project_number", "mobilesdk_app_id", "client_id" and still no "google_app_id" property.
Is it ok with unique value of each apps? If so, it'll be working with project id or number, but I'm not sure.
Thank you in advance.