What Does _apply Plugin: 'com.google.gms.google-services'_ Do?

What does exactly adding apply plugin: 'com.google.gms.google-services' do? If I comment this, my app still will compile and run. More about adding Firebase to the project here.

Solution 1:

It reads resources out of your google-services.json file as described here. It also adds a compile dependency on firebase-core if not already present. That dependency will cause FirebaseInitProvider to get merged into your manifest, which is responsible for initializing a default FirebaseApp at app launch with the resources it read during the build phase.

If you want to learn more about Firebase app init, read:

• How does Firebase initialize on Android?
• Take Control of Your Firebase Init on Android