Although there are many answers on how to restrict the API to only a specific country, couldn't find anything regarding restricting it to the train stations. Please help me out on this. Thanks.
I think this is not supported in the API at the moment.
I can see a feature request to enable this feature in Places API web service:
https://issuetracker.google.com/issues/35820774
I would suggest filing the same feature request for Places API for Android autocomplete.
You can also see similar feature requests for PlacePickers in Android and iOS:
来源：https://stackoverflow.com/questions/46292779/how-to-restrict-android-google-autocomplete-api-to-only-get-train-stations