Retrieving external applications information

I would like to know if th开发者_C百科ere is anyway if collecting information of applications which installed on the phone?(thigns like: activities names, permissions the app using, services, etc...)

I tried to look little bit at packageManager and packageInfo.. but when i tried to use those methods i mostly got NULL.

anything you ppl know about?

Thanks,

ray.

 PackageManager pm = context.getPackageManager();
 PackageInfo pi = pm.getPackageInfo(..)

a way of retrieving some information