A question of optimisation and memory

I want to know when im starting an activity using an Intent is t开发者_C百科he main activity(main) still in memory when im in subactivity?

Read basics related to activity Lifecycle http://developer.android.com/reference/android/app/Activity.html If you want to clear(close) main-activity after starting new one(sub-activity) using intent, then you have to close it(main activity) manually. Android is going to take care of that all things related to activity lifecycle, why you want to close main-activity?