8.24.2015

portrait: vertically

landscape: horizentally

activity: an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map.

main activity: application 처음 launch 할 때 나오는 activity

새로운 activity 시작 할 때 마다, 이전 activity는 stop 하고 stack (the "back stack")에 보존 & 변화 ​activity's lifecycle callback methods 로 알린다.

activity 만들 때

a subclass of Activity

callback methods 있어야 한다(상태 변화 보고)

onCreate(): setContentView() 있어야 함

onPause(): user가 떠날 때 

view

ready-made view

Widgets: button, textfield 등등

Layouts(ViewGroup): linear layout, grid layout 등등

xml layout file 만들기 -> setContentView()로 불러오기

(source: http://developer.android.com/guide/components/activities.html#Lifecycle)

configuration 바꿀 때:

onDestroy() ,onCreate()