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PagerAdapter

public abstract class PagerAdapter
extends Object

java.lang.Object
↳	android.support.v4.view.PagerAdapter

Known Direct Subclasses

FragmentPagerAdapter, FragmentStatePagerAdapter

Base class providing the adapter to populate pages inside of a ViewPager. You will most likely want to use a more specific implementation of this, such as FragmentPagerAdapter or FragmentStatePagerAdapter.

When you implement a PagerAdapter, you must override the following methods at minimum:

PagerAdapter is more general than the adapters used for AdapterViews. Instead of providing a View recycling mechanism directly ViewPager uses callbacks to indicate the steps taken during an update. A PagerAdapter may implement a form of View recycling if desired or use a more sophisticated method of managing page Views such as Fragment transactions where each page is represented by its own Fragment.

ViewPager associates each page with a key Object instead of working with Views directly. This key is used to track and uniquely identify a given page independent of its position in the adapter. A call to the PagerAdapter method startUpdate(ViewGroup) indicates that the contents of the ViewPager are about to change. One or more calls to instantiateItem(ViewGroup, int) and/or destroyItem(ViewGroup, int, Object) will follow, and the end of an update will be signaled by a call to finishUpdate(ViewGroup). By the time finishUpdate returns the views associated with the key objects returned by instantiateItem should be added to the parent ViewGroup passed to these methods and the views associated with the keys passed to destroyItem should be removed. The method isViewFromObject(View, Object) identifies whether a page View is associated with a given key object.

A very simple PagerAdapter may choose to use the page Views themselves as key objects, returning them from instantiateItem(ViewGroup, int) after creation and adding them to the parent ViewGroup. A matching destroyItem(ViewGroup, int, Object) implementation would remove the View from the parent ViewGroup and isViewFromObject(View, Object) could be implemented as return view == object;.

PagerAdapter supports data set changes. Data set changes must occur on the main thread and must end with a call to notifyDataSetChanged() similar to AdapterView adapters derived from BaseAdapter. A data set change may involve pages being added, removed, or changing position. The ViewPager will keep the current page active provided the adapter implements the method getItemPosition(Object).

Summary

Constants
`int`	`POSITION_NONE`
`int`	`POSITION_UNCHANGED`

Public constructors
`PagerAdapter()`

Public methods
`void`	`destroyItem(View container, int position, Object object)` This method is deprecated. Use `destroyItem(ViewGroup, int, Object)`
`void`	`destroyItem(ViewGroup container, int position, Object object)` Remove a page for the given position.
`void`	`finishUpdate(View container)` This method is deprecated. Use `finishUpdate(ViewGroup)`
`void`	`finishUpdate(ViewGroup container)` Called when the a change in the shown pages has been completed.
`abstract int`	`getCount()` Return the number of views available.
`int`	`getItemPosition(Object object)` Called when the host view is attempting to determine if an item's position has changed.
`CharSequence`	`getPageTitle(int position)` This method may be called by the ViewPager to obtain a title string to describe the specified page.
`float`	`getPageWidth(int position)` Returns the proportional width of a given page as a percentage of the ViewPager's measured width from (0.f-1.f]
`Object`	`instantiateItem(ViewGroup container, int position)` Create the page for the given position.
`Object`	`instantiateItem(View container, int position)` This method is deprecated. Use `instantiateItem(ViewGroup, int)`
`abstract boolean`	`isViewFromObject(View view, Object object)` Determines whether a page View is associated with a specific key object as returned by `instantiateItem(ViewGroup, int)`.
`void`	`notifyDataSetChanged()` This method should be called by the application if the data backing this adapter has changed and associated views should update.
`void`	`registerDataSetObserver(DataSetObserver observer)` Register an observer to receive callbacks related to the adapter's data changing.
`void`	`restoreState(Parcelable state, ClassLoader loader)` Restore any instance state associated with this adapter and its pages that was previously saved by `saveState()`.
`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(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`	`setPrimaryItem(View container, int position, Object object)` This method is deprecated. Use `setPrimaryItem(ViewGroup, int, Object)`
`void`	`startUpdate(ViewGroup container)` Called when a change in the shown pages is going to start being made.
`void`	`startUpdate(View container)` This method is deprecated. Use `startUpdate(ViewGroup)`
`void`	`unregisterDataSetObserver(DataSetObserver observer)` Unregister an observer from callbacks related to the adapter's data changing.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Constants

POSITION_NONE

int POSITION_NONE

Constant Value: -2 (0xfffffffe)

POSITION_UNCHANGED

int POSITION_UNCHANGED

Constant Value: -1 (0xffffffff)

Public constructors

PagerAdapter

PagerAdapter ()

Public methods

destroyItem

void destroyItem (View container, 
                int position, 
                Object object)

This method is deprecated.
Use destroyItem(ViewGroup, int, Object)

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 finishUpdate(View).

Parameters
`container`	`View`: The containing View from which the page will be removed.
`position`	`int`: The page position to be removed.
`object`	`Object`: The same object that was returned by `instantiateItem(View, int)`.

destroyItem

void destroyItem (ViewGroup container, 
                int position, 
                Object object)

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 finishUpdate(ViewGroup).

Parameters
`container`	`ViewGroup`: The containing View from which the page will be removed.
`position`	`int`: The page position to be removed.
`object`	`Object`: The same object that was returned by `instantiateItem(View, int)`.

finishUpdate

void finishUpdate (View container)

This method is deprecated.
Use finishUpdate(ViewGroup)

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.

Parameters
`container`	`View`: The containing View which is displaying this adapter's page views.

finishUpdate

void finishUpdate (ViewGroup container)

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.

Parameters
`container`	`ViewGroup`: The containing View which is displaying this adapter's page views.

getCount

int getCount ()

Return the number of views available.

Returns
`int`

getItemPosition

int getItemPosition (Object object)

Called when the host view is attempting to determine if an item's position has changed. Returns POSITION_UNCHANGED if the position of the given item has not changed or POSITION_NONE if the item is no longer present in the adapter.

The default implementation assumes that items will never change position and always returns POSITION_UNCHANGED.

Parameters
`object`	`Object`: Object representing an item, previously returned by a call to `instantiateItem(View, int)`.

Returns
`int`	object's new position index from [0, `getCount()`), `POSITION_UNCHANGED` if the object's position has not changed, or `POSITION_NONE` if the item is no longer present.

getPageTitle

CharSequence getPageTitle (int position)

This method may be called by the ViewPager to obtain a title string to describe the specified page. This method may return null indicating no title for this page. The default implementation returns null.

Parameters
`position`	`int`: The position of the title requested

Returns
`CharSequence`	A title for the requested page

getPageWidth

float getPageWidth (int position)

Returns the proportional width of a given page as a percentage of the ViewPager's measured width from (0.f-1.f]

Parameters
`position`	`int`: The position of the page requested

Returns
`float`	Proportional width for the given page position

instantiateItem

Object instantiateItem (ViewGroup container, 
                int position)

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 finishUpdate(ViewGroup).

Parameters
`container`	`ViewGroup`: The containing View in which the page will be shown.
`position`	`int`: The page position to be instantiated.

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

instantiateItem

Object instantiateItem (View container, 
                int position)

This method is deprecated.
Use instantiateItem(ViewGroup, int)

Parameters
`container`	`View`: The containing View in which the page will be shown.
`position`	`int`: The page position to be instantiated.

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

isViewFromObject

boolean isViewFromObject (View view, 
                Object object)

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

Parameters
`view`	`View`: Page View to check for association with `object`
`object`	`Object`: Object to check for association with `view`

Returns
`boolean`	true if `view` is associated with the key object `object`

notifyDataSetChanged

void notifyDataSetChanged ()

This method should be called by the application if the data backing this adapter has changed and associated views should update.

registerDataSetObserver

void registerDataSetObserver (DataSetObserver observer)

Parameters
`observer`	`DataSetObserver`: The `DataSetObserver` which will receive callbacks.

restoreState

void restoreState (Parcelable state, 
                ClassLoader loader)

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

Parameters
`state`	`Parcelable`: State previously saved by a call to `saveState()`
`loader`	`ClassLoader`: A ClassLoader that should be used to instantiate any restored objects

saveState

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.

Returns
`Parcelable`	Saved state for this adapter

setPrimaryItem

void setPrimaryItem (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.

Parameters
`container`	`ViewGroup`: The containing View from which the page will be removed.
`position`	`int`: The page position that is now the primary.
`object`	`Object`: The same object that was returned by `instantiateItem(View, int)`.

setPrimaryItem

void setPrimaryItem (View container, 
                int position, 
                Object object)

This method is deprecated.
Use setPrimaryItem(ViewGroup, int, 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.

Parameters
`container`	`View`: The containing View from which the page will be removed.
`position`	`int`: The page position that is now the primary.
`object`	`Object`: The same object that was returned by `instantiateItem(View, int)`.

startUpdate

void startUpdate (ViewGroup container)

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

Parameters
`container`	`ViewGroup`: The containing View which is displaying this adapter's page views.

startUpdate

void startUpdate (View container)

This method is deprecated.
Use startUpdate(ViewGroup)

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

Parameters
`container`	`View`: The containing View which is displaying this adapter's page views.

unregisterDataSetObserver

void unregisterDataSetObserver (DataSetObserver observer)

Unregister an observer from callbacks related to the adapter's data changing.

Parameters
`observer`	`DataSetObserver`: The `DataSetObserver` which will be unregistered.

Annotations

Interfaces

Classes

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Results for

PagerAdapter

Summary

Constants

Public constructors

Public methods

Inherited methods

Constants

POSITION_NONE

POSITION_UNCHANGED

Public constructors

PagerAdapter

Public methods

destroyItem

destroyItem

finishUpdate

finishUpdate

getCount

getItemPosition

getPageTitle

getPageWidth

instantiateItem

instantiateItem

isViewFromObject

notifyDataSetChanged

registerDataSetObserver

restoreState

saveState

setPrimaryItem

setPrimaryItem

startUpdate

startUpdate

unregisterDataSetObserver