Check if point is in polygon with Google Maps API in Android

You can use the PolyUtil.containsLocation method from the Google Maps Android API Utility Library. From the documentation:

public static boolean containsLocation(LatLng point, java.util.List polygon, boolean geodesic)

Computes whether the given point lies inside the specified polygon. The polygon is always considered closed, regardless of whether the last point equals the first or not. Inside is defined as not containing the South Pole -- the South Pole is always outside. The polygon is formed of great circle segments if geodesic is true, and of rhumb (loxodromic) segments otherwise.

A bit later response, but for future searches, you can also check if a location is inside the current visible map area by using:

// Kotlin code
var location = LatLng(-27.6016488, -48.5137219)    
val isInside = mGoogleMap.projection.visibleRegion.latLngBounds.contains(location)

Documentation link: contains (LatLng point)