application always on foreground or on focused or ontop

I'm trying to create a simple android application which should always be in foreground running... no one can kill this application if started once. or it can be closed only wh开发者_如何学Goen device get restarted.

I'm working with eclipse and android 2.3 api 9.

The Android system does not really allow this sort of behavior for an application. The home button is always going to remove your app from the foreground and take the user to the home screen. If you want to develop an app like this you're probably going to have to do it under a modified version of the OS to allow such things.