How to know how many applications are running in the background in android?

Question

I can run an application in background but I want to know how many applications are running in the background. Like in some mobile while pressing the center button a list of currently running applications are displayed.

Is this is possible in android? If possible then give some code snippets and steps to achieve this.

Answer 1

The Dev Tools application (installed in emulators) shows a list of running processes by obtaining an instance of ActivityManager:

ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningAppProcessInfo> l = am.getRunningAppProcesses();