Detect whenever user opens a foreground app

I am developing an android app. I开发者_JAVA百科 want to know through an event or any other means in my service, whenever user opens a foreground app. I want to collect my own usage statistics, as I can't find a way to know how many times an app has been used.

Does anyone know of a nice way to do this? Or obtain those statistics, already, if possible?

None of this is supported by the Android SDK.

Have you tried Google Analytics directly?

http://code.google.com/mobile/analytics/docs/android/