FragmentStateAdapter

public abstract class FragmentStateAdapter
extends Adapter<FragmentViewHolder> implements StatefulAdapter

java.lang.Object
   ↳ androidx.recyclerview.widget.RecyclerView.Adapter<androidx.viewpager2.adapter.FragmentViewHolder>
     ↳ androidx.viewpager2.adapter.FragmentStateAdapter


Similar in behavior to FragmentStatePagerAdapter

Lifecycle within RecyclerView:

Summary

Public constructors

FragmentStateAdapter(FragmentActivity fragmentActivity)
FragmentStateAdapter(Fragment fragment)
FragmentStateAdapter(FragmentManager fragmentManager, Lifecycle lifecycle)

Public methods

boolean containsItem(long itemId)

Default implementation works for collections that don't add, move, remove items.

abstract Fragment getItem(int position)

Provide a Fragment associated with the specified position.

long getItemId(int position)

Default implementation works for collections that don't add, move, remove items.

final void onBindViewHolder(FragmentViewHolder holder, int position)

Called by RecyclerView to display the data at the specified position.

final FragmentViewHolder onCreateViewHolder(ViewGroup parent, int viewType)

Called when RecyclerView needs a new RecyclerView.ViewHolder of the given type to represent an item.

final boolean onFailedToRecycleView(FragmentViewHolder holder)

Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state.

final void onViewAttachedToWindow(FragmentViewHolder holder)

Called when a view created by this adapter has been attached to a window.

final void onViewRecycled(FragmentViewHolder holder)

Called when a view created by this adapter has been recycled.

void restoreState(Parcelable savedState)

Restores adapter state

Parcelable saveState()

Saves adapter state

final void setHasStableIds(boolean hasStableIds)

Indicates whether each item in the data set can be represented with a unique identifier of type Long.

Inherited methods

Public constructors

FragmentStateAdapter

public FragmentStateAdapter (FragmentActivity fragmentActivity)

Parameters
fragmentActivity FragmentActivity: if the ViewPager2 lives directly in a FragmentActivity subclass.

FragmentStateAdapter

public FragmentStateAdapter (Fragment fragment)

Parameters
fragment Fragment: if the ViewPager2 lives directly in a Fragment subclass.

FragmentStateAdapter

public FragmentStateAdapter (FragmentManager fragmentManager, 
                Lifecycle lifecycle)

Parameters
fragmentManager FragmentManager: of ViewPager2's host

lifecycle Lifecycle: of ViewPager2's host

Public methods

containsItem

public boolean containsItem (long itemId)

Default implementation works for collections that don't add, move, remove items.

TODO(b/122670460): add lint rule When overriding, also override getItemId(int)

Parameters
itemId long

Returns
boolean

getItem

public abstract Fragment getItem (int position)

Provide a Fragment associated with the specified position.

Parameters
position int

Returns
Fragment

getItemId

public long getItemId (int position)

Default implementation works for collections that don't add, move, remove items.

TODO(b/122670460): add lint rule When overriding, also override containsItem(long).

If the item is not a part of the collection, return RecyclerView.NO_ID.

Parameters
position int: Adapter position

Returns
long stable item id RecyclerView.Adapter.hasStableIds()

onBindViewHolder

public final void onBindViewHolder (FragmentViewHolder holder, 
                int position)

Called by RecyclerView to display the data at the specified position. This method should update the contents of the RecyclerView.ViewHolder.itemView to reflect the item at the given position.

Note that unlike ListView, RecyclerView will not call this method again if the position of the item changes in the data set unless the item itself is invalidated or the new position cannot be determined. For this reason, you should only use the position parameter while acquiring the related data item inside this method and should not keep a copy of it. If you need the position of an item later on (e.g. in a click listener), use RecyclerView.ViewHolder.getAdapterPosition() which will have the updated adapter position. Override onBindViewHolder(ViewHolder, int, List) instead if Adapter can handle efficient partial bind.

Parameters
holder FragmentViewHolder: The ViewHolder which should be updated to represent the contents of the item at the given position in the data set.

position int: The position of the item within the adapter's data set.

onCreateViewHolder

public final FragmentViewHolder onCreateViewHolder (ViewGroup parent, 
                int viewType)

Called when RecyclerView needs a new RecyclerView.ViewHolder of the given type to represent an item.

This new ViewHolder should be constructed with a new View that can represent the items of the given type. You can either create a new View manually or inflate it from an XML layout file.

The new ViewHolder will be used to display items of the adapter using onBindViewHolder(ViewHolder, int, List). Since it will be re-used to display different items in the data set, it is a good idea to cache references to sub views of the View to avoid unnecessary View.findViewById(int) calls.

Parameters
parent ViewGroup: The ViewGroup into which the new View will be added after it is bound to an adapter position.

viewType int: The view type of the new View.

Returns
FragmentViewHolder A new ViewHolder that holds a View of the given view type.

onFailedToRecycleView

public final boolean onFailedToRecycleView (FragmentViewHolder holder)

Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state. Upon receiving this callback, Adapter can clear the animation(s) that effect the View's transient state and return true so that the View can be recycled. Keep in mind that the View in question is already removed from the RecyclerView.

In some cases, it is acceptable to recycle a View although it has transient state. Most of the time, this is a case where the transient state will be cleared in onBindViewHolder(ViewHolder, int) call when View is rebound to a new position. For this reason, RecyclerView leaves the decision to the Adapter and uses the return value of this method to decide whether the View should be recycled or not.

Note that when all animations are created by RecyclerView.ItemAnimator, you should never receive this callback because RecyclerView keeps those Views as children until their animations are complete. This callback is useful when children of the item views create animations which may not be easy to implement using an RecyclerView.ItemAnimator.

You should never fix this issue by calling holder.itemView.setHasTransientState(false); unless you've previously called holder.itemView.setHasTransientState(true);. Each View.setHasTransientState(true) call must be matched by a View.setHasTransientState(false) call, otherwise, the state of the View may become inconsistent. You should always prefer to end or cancel animations that are triggering the transient state instead of handling it manually.

Parameters
holder FragmentViewHolder: The ViewHolder containing the View that could not be recycled due to its transient state.

Returns
boolean True if the View should be recycled, false otherwise. Note that if this method returns true, RecyclerView will ignore the transient state of the View and recycle it regardless. If this method returns false, RecyclerView will check the View's transient state again before giving a final decision. Default implementation returns false.

onViewAttachedToWindow

public final void onViewAttachedToWindow (FragmentViewHolder holder)

Called when a view created by this adapter has been attached to a window.

This can be used as a reasonable signal that the view is about to be seen by the user. If the adapter previously freed any resources in onViewDetachedFromWindow those resources should be restored here.

Parameters
holder FragmentViewHolder: Holder of the view being attached

onViewRecycled

public final void onViewRecycled (FragmentViewHolder holder)

Called when a view created by this adapter has been recycled.

A view is recycled when a RecyclerView.LayoutManager decides that it no longer needs to be attached to its parent RecyclerView. This can be because it has fallen out of visibility or a set of cached views represented by views still attached to the parent RecyclerView. If an item view has large or expensive data bound to it such as large bitmaps, this may be a good place to release those resources.

RecyclerView calls this method right before clearing ViewHolder's internal data and sending it to RecycledViewPool. This way, if ViewHolder was holding valid information before being recycled, you can call RecyclerView.ViewHolder.getAdapterPosition() to get its adapter position.

Parameters
holder FragmentViewHolder: The ViewHolder for the view being recycled

restoreState

public void restoreState (Parcelable savedState)

Restores adapter state

Parameters
savedState Parcelable

saveState

public Parcelable saveState ()

Saves adapter state

Returns
Parcelable

setHasStableIds

public final void setHasStableIds (boolean hasStableIds)

Indicates whether each item in the data set can be represented with a unique identifier of type Long.

Parameters
hasStableIds boolean: Whether items in data set have unique identifiers or not.