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.
When everything else fails, go to the roots:
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/2.3.4_r1/android/net/wifi/WifiManager.java#WifiManager.startScanActive%28%29
It is a public method in WifiManager since 1.6, although you're correct in saying that Eclipse does not find that method, for some weird reason.