android.support.v4.app
Class FragmentStatePagerAdapter

java.lang.Object
  android.support.v4.view.PagerAdapter
      android.support.v4.app.FragmentStatePagerAdapter

public abstract class FragmentStatePagerAdapter
extends PagerAdapter

Implementation of PagerAdapter that uses a Fragment to manage each page. This class also handles saving and restoring of fragment's state.

This version of the pager is more useful when there are a large number of pages, working more like a list view. When pages are not visible to the user, their entire fragment may be destroyed, only keeping the saved state of that fragment. This allows the pager to hold on to much less memory associated with each visited page as compared to FragmentPagerAdapter at the cost of potentially more overhead when switching between pages.

When using FragmentPagerAdapter the host ViewPager must have a valid ID set.

Subclasses only need to implement getItem(int) and PagerAdapter.getCount() to have a working adapter.

Here is an example implementation of a pager containing fragments of lists:

The R.layout.fragment_pager resource of the top-level fragment is:

The R.layout.fragment_pager_list resource containing each individual fragment's layout is:

Field Summary

Fields inherited from class android.support.v4.view.PagerAdapter

POSITION_NONE, POSITION_UNCHANGED

Constructor Summary

FragmentStatePagerAdapter(FragmentManager fm)

Method Summary

void	destroyItem(android.view.ViewGroup container, int position, Object object) Remove a page for the given position.
void	finishUpdate(android.view.ViewGroup container) Called when the a change in the shown pages has been completed.
abstract Fragment	getItem(int position) Return the Fragment associated with a specified position.
Object	instantiateItem(android.view.ViewGroup container, int position) Create the page for the given position.
boolean	isViewFromObject(android.view.View view, Object object) Determines whether a page View is associated with a specific key object as returned by PagerAdapter.instantiateItem(ViewGroup, int).
void	restoreState(android.os.Parcelable state, ClassLoader loader) Restore any instance state associated with this adapter and its pages that was previously saved by PagerAdapter.saveState().
android.os.Parcelable	saveState() Save any instance state associated with this adapter and its pages that should be restored if the current UI state needs to be reconstructed.
void	setPrimaryItem(android.view.ViewGroup container, int position, Object object) Called to inform the adapter of which item is currently considered to be the "primary", that is the one show to the user as the current page.
void	startUpdate(android.view.ViewGroup container) Called when a change in the shown pages is going to start being made.

Methods inherited from class android.support.v4.view.PagerAdapter

destroyItem, finishUpdate, getCount, getItemPosition, getPageTitle, getPageWidth, instantiateItem, notifyDataSetChanged, registerDataSetObserver, setPrimaryItem, startUpdate, unregisterDataSetObserver

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FragmentStatePagerAdapter

public FragmentStatePagerAdapter(FragmentManager fm)

Method Detail

getItem

public abstract Fragment getItem(int position)

Return the Fragment associated with a specified position.

startUpdate

public void startUpdate(android.view.ViewGroup container)

Description copied from class: PagerAdapter

Called when a change in the shown pages is going to start being made.

Overrides:

startUpdate in class PagerAdapter

Parameters:

container - The containing View which is displaying this adapter's page views.

instantiateItem

public Object instantiateItem(android.view.ViewGroup container,
                              int position)

Description copied from class: PagerAdapter

Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns from PagerAdapter.finishUpdate(ViewGroup).

Overrides:

instantiateItem in class PagerAdapter

Parameters:

container - The containing View in which the page will be shown.

position - The page position to be instantiated.

Returns:

Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page.

destroyItem

public void destroyItem(android.view.ViewGroup container,
                        int position,
                        Object object)

Description copied from class: PagerAdapter

Remove a page for the given position. The adapter is responsible for removing the view from its container, although it only must ensure this is done by the time it returns from PagerAdapter.finishUpdate(ViewGroup).

Overrides:

destroyItem in class PagerAdapter

Parameters:

container - The containing View from which the page will be removed.

position - The page position to be removed.

object - The same object that was returned by PagerAdapter.instantiateItem(View, int).

setPrimaryItem

public void setPrimaryItem(android.view.ViewGroup container,
                           int position,
                           Object object)

Description copied from class: PagerAdapter

Called to inform the adapter of which item is currently considered to be the "primary", that is the one show to the user as the current page.

Overrides:

setPrimaryItem in class PagerAdapter

Parameters:

container - The containing View from which the page will be removed.

position - The page position that is now the primary.

object - The same object that was returned by PagerAdapter.instantiateItem(View, int).

finishUpdate

public void finishUpdate(android.view.ViewGroup container)

Description copied from class: PagerAdapter

Called when the a change in the shown pages has been completed. At this point you must ensure that all of the pages have actually been added or removed from the container as appropriate.

Overrides:

finishUpdate in class PagerAdapter

Parameters:

container - The containing View which is displaying this adapter's page views.

isViewFromObject

public boolean isViewFromObject(android.view.View view,
                                Object object)

Description copied from class: PagerAdapter

Determines whether a page View is associated with a specific key object as returned by PagerAdapter.instantiateItem(ViewGroup, int). This method is required for a PagerAdapter to function properly.

Specified by:

isViewFromObject in class PagerAdapter

Parameters:

view - Page View to check for association with object

object - Object to check for association with view

Returns:

true if view is associated with the key object object

saveState

public android.os.Parcelable saveState()

Description copied from class: PagerAdapter

Save any instance state associated with this adapter and its pages that should be restored if the current UI state needs to be reconstructed.

Overrides:

saveState in class PagerAdapter

Returns:

Saved state for this adapter

restoreState

public void restoreState(android.os.Parcelable state,
                         ClassLoader loader)

Description copied from class: PagerAdapter

Restore any instance state associated with this adapter and its pages that was previously saved by PagerAdapter.saveState().

Overrides:

restoreState in class PagerAdapter

Parameters:

state - State previously saved by a call to PagerAdapter.saveState()

loader - A ClassLoader that should be used to instantiate any restored objects