On the site androidjavadoc.com, a method startScanActive is listed in the class WifiManager that makes it possible to perform an active wi-fi scan.
As I mentioned, look at the official documentation. It's not there. As such, it's not part of the public API, and you should not call it. Even if it's public, it doesn't mean that you can call it.
Undocumented API calls can disappear without notice at any time in future versions, which will cause your app to break.