Basic understanding of Android Fragments and its State

What is Fragment and why did it come into existence?

Fragment is one of the highly used class/component in the current mobile and Tab application development. Its has increased the development and usability up to a right scale.  Android introduced fragments in Android 3.0 (API level 11), primarily to support more dynamic and flexible UI designs on large screens, such as tablets. Because a tablet's screen is much larger than that of a handset, there's more room to combine and interchange UI components. Fragments allow such designs without the need for you to manage complex changes to the view hierarchy. By dividing the layout of an activity into fragments, you become able to modify the activity's appearance at runtime and preserve those changes in a back stack that's managed by the activity.

For example, a news application can use one fragment to show a list of articles on the left and another fragment to display an article on the right—both fragments appear in one activity, side by side, and each fragment has its own set of lifecycle callback methods and handle their own user input events. Thus, instead of using one activity to select an article and another activity to read the article, the user can select an article and read it all within the same activity, as illustrated in the tablet layout in figure 1.

Fragment States :

Fragment class has almost similar class as Activity class. Overall an activity contains the 7 7 life cycle state and a Fragment contains 11 lifecycle state.

Activity States : 

1. onCreate()
2. onStart()
3. onResume()
4. onPause()
5. onStop()
6. onRestart()
7. onDestroy()

To Understand the full flow use the following link.

http://developer.android.com/reference/android/app/Activity.html

Fragment States:

1. onAttach()
2. onCreate()
3. onCreateView()
4. onActivityCreated()
5. onStart()
6. onResume()
7. onPause()
8. onStop()
9. onDestroyView()
10. onDestroy()
11. onDetach()

onAttach()

Called when the fragment has been associated with the activity (the Activity is passed in here).

onCreateView()

Called to create the view hierarchy associated with the fragment.

onActivityCreated()

Called when the activity's  onCreate() method has returned.
onDestroyView()
Called when the view hierarchy associated with the fragment is being removed.

onDetach()
          Called when the fragment is detached from Activity.