LIFE CYCLE OF AN ACTIVITY

Activities are placed in the form of backstack.Whenever, an activity is displayed its object is first created in memory.

1.  onCreate() : state when object of an activity is created by Android system.
2. onStart() : Activity is visible to user but user can’t interact.
3. onResume() : When object of Activity is visible and user can interact through GUI.
4. onPause() : When Object of activity is visible but user can’t interact.
5. onStop() : Object of activity is not visible and user can’t interact with it.
6. onDestroy() : Object of activity is destroyed.

 

INTRODUCTION TO ANDROID

Android is open-source Linux based OS for smartphones and tablet computers.

ANDROID ARCHITECTURE

1. LINUX KERNEL : Responsible for drivers,  memory management, device management.
2. NATIVE LIBRARIES : There are libraries including  WebKit, SQLite database , SSL libraries..
3. ANDROID RUNTIME : DVM (Dalvik Virtual Machine) which is responsible to run android application.
4. ANDROID FRAMEWORK : Includes Android API’s such as UI ,telephony, resources.
5. APPLICATIONS : Applications such as home, contact, settings, games, browsers.

APPLICATION COMPONENTS

1. Activity : Handles UI
2. Service : Handle background processes associated with an App.
3. Broadcast Receiver : Handles communication between Android OS and App.
4. Content Provider : Handle data and data base management.

For Basic  Android development ,  two languages are needed.

For front end – Xml

For back end – Java