universum.studios.android.pager.adapter

Class FragmentPagerAdapter

java.lang.Object

androidx.viewpager.widget.PagerAdapter

universum.studios.android.pager.adapter.FragmentPagerAdapter

public abstract class FragmentPagerAdapter
extends androidx.viewpager.widget.PagerAdapter

A PagerAdapter implementation that represents each page as a Fragment that is persistently kept in the fragment manager as long as a user can return to the page.

This version of the pager adapter is best for use when there are a handful of typically more static fragments to be paged through, such as a set of tabs. The fragment of each page the user visits will be kept in memory, though its view hierarchy may be destroyed when not visible. This can result in using a significant amount of memory since fragment instances can hold on to an arbitrary amount of state. For larger sets of pages, consider FragmentStatePagerAdapter.

Note, that when using FragmentPagerAdapter, the host ViewPager must have a valid ID set, otherwise this adapter implementation will throw an exception.

The inheritance hierarchies only need to implement getItem(int) and PagerAdapter.getCount() to become a fully working adapters.

Since:

1.0

Author:

Martin Albedinsky

Field Summary

Fields

Modifier and Type	Field and Description
static long	NO_ID Constant used to identify unspecified id.
static int	NO_POSITION Constant used to identify unspecified position.

Fields inherited from class androidx.viewpager.widget.PagerAdapter

POSITION_NONE, POSITION_UNCHANGED

Constructor Summary

Constructors

Constructor and Description
FragmentPagerAdapter(androidx.fragment.app.FragmentManager fragmentManager) Creates a new instance of FragmentPagerAdapter with the specified fragmentManager.

Method Summary

Modifier and Type	Method and Description
void	destroyItem(android.view.ViewGroup container, int position, Object object)
void	finishUpdate(android.view.ViewGroup container)
abstract androidx.fragment.app.Fragment	getItem(int position) Instantiates a new Fragment associated with the specified position.
long	getItemId(int position) Returns a unique identifier for the item at the specified position.
androidx.fragment.app.Fragment	getPrimaryFragment() Returns the fragment instance that has been set as primary item via setPrimaryItem(ViewGroup, int, Object).
int	getPrimaryPosition() Returns position of the current primary item.
Object	instantiateItem(android.view.ViewGroup container, int position)
boolean	isViewFromObject(android.view.View view, Object object)
protected String	makeItemTag(int containerId, long itemId) Makes a tag for an item with the given itemId.
protected void	setMakeItemTags(boolean makeItemTags) Sets a boolean flag indicating whether this pager adapter should make tags for its items or not.
void	setPrimaryItem(android.view.ViewGroup container, int position, Object object)
void	startUpdate(android.view.ViewGroup container)

Methods inherited from class androidx.viewpager.widget.PagerAdapter

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

Methods inherited from class java.lang.Object

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

Field Detail

NO_POSITION

public static final int NO_POSITION

Constant used to identify unspecified position.

See Also:

Constant Field Values

NO_ID

public static final long NO_ID

Constant used to identify unspecified id.

See Also:

Constant Field Values

Constructor Detail

FragmentPagerAdapter

public FragmentPagerAdapter(@NonNull
                            androidx.fragment.app.FragmentManager fragmentManager)

Creates a new instance of FragmentPagerAdapter with the specified fragmentManager.

Parameters:

fragmentManager - The manager used to manage fragments provided by the pager adapter.

Method Detail

startUpdate

public void startUpdate(@NonNull
                        android.view.ViewGroup container)

Overrides:

startUpdate in class androidx.viewpager.widget.PagerAdapter

instantiateItem

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

Overrides:

instantiateItem in class androidx.viewpager.widget.PagerAdapter

setMakeItemTags

protected final void setMakeItemTags(boolean makeItemTags)

Sets a boolean flag indicating whether this pager adapter should make tags for its items or not.

This feature is by default enabled.

Parameters:

makeItemTags - True to enable making of item tags, false otherwise.

See Also:

makeItemTag(int, long)

makeItemTag

@Nullable
protected String makeItemTag(@IdRes
                                       int containerId,
                                       long itemId)

Makes a tag for an item with the given itemId.

By default making of item tags is enabled and the default implementation makes tag in the following format:

 "android:pager:CONTAINER_ID:ITEM_ID"
 

This feature may be enabled/disabled via setMakeItemTags(boolean).

Parameters:

containerId - Id of the associated view pager container.

itemId - Id of the item for which to create its corresponding tag.

Returns:

Item's tag or null if this adapter does not create tags for its items.

getItemId

public long getItemId(int position)

Returns a unique identifier for the item at the specified position.

The default implementation returns the given position. The inheritance hierarchies should override this method if they have better way to uniquely identify their items.

Note that this method may be called also from destroyItem(ViewGroup, int, Object) when, possibly, the data set of this adapter may be already invalid. In such case it is safe to return NO_ID.

Parameters:

position - Position from the range of size of items of this adapter.

Returns:

Unique identifier for the item at the requested position.

getItem

@NonNull
public abstract androidx.fragment.app.Fragment getItem(int position)

Instantiates a new Fragment associated with the specified position.

See Also:

instantiateItem(ViewGroup, int)

setPrimaryItem

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

Overrides:

setPrimaryItem in class androidx.viewpager.widget.PagerAdapter

getPrimaryFragment

@Nullable
public androidx.fragment.app.Fragment getPrimaryFragment()

Returns the fragment instance that has been set as primary item via setPrimaryItem(ViewGroup, int, Object).

Returns:

Currently primary fragment. May be null if no primary item has been set yet.

See Also:

getPrimaryPosition()

getPrimaryPosition

public int getPrimaryPosition()

Returns position of the current primary item.

Returns:

Primary item's position or NO_POSITION if no primary item has been specified yet.

See Also:

getPrimaryFragment(), setPrimaryItem(ViewGroup, int, Object)

isViewFromObject

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

Specified by:

isViewFromObject in class androidx.viewpager.widget.PagerAdapter

destroyItem

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

Overrides:

destroyItem in class androidx.viewpager.widget.PagerAdapter

finishUpdate

public void finishUpdate(@NonNull
                         android.view.ViewGroup container)

Overrides:

finishUpdate in class androidx.viewpager.widget.PagerAdapter