The entry point of Firebase SDKs. It holds common configuration and state for Firebase APIs. Most applications don't need to directly interact with FirebaseApp.

For a vast majority of apps, FirebaseInitProvider will handle the initialization of Firebase for the default project that it's configured to work with, via the data contained in the app's google-services.json file. This ContentProvider is merged into the app's manifest by default when building with Gradle, and it runs automatically at app launch. No additional lines of code are needed in this case.

In the event that an app requires access to another Firebase project in addition to the default project, initializeApp(Context, FirebaseOptions, String) must be used to create that relationship programmatically. The name parameter must be unique. To connect to the resources exposed by that project, use the FirebaseApp object returned by getInstance(String), passing it the same name used with initializeApp. This object must be passed to the static accessor of the feature that provides the resource. For example, getInstance(FirebaseApp) is used to access the storage bucket provided by the additional project, whereas getInstance() is used to access the default project.

Any FirebaseApp initialization must occur only in the main process of the app. Use of Firebase in processes other than the main process is not supported and will likely cause problems related to resource contention.