FragmentStateAdapter


abstract class FragmentStateAdapter : RecyclerView.Adapter, StatefulAdapter


Similar in behavior to FragmentStatePagerAdapter

Lifecycle within RecyclerView:

Summary

Nested types

@RequiresOptIn(level = RequiresOptIn.Level.WARNING)
annotation FragmentStateAdapter.ExperimentalFragmentStateAdapterApi

Callback interface for listening to fragment lifecycle changes that happen inside the adapter.

Callback returned by onFragmentPreAdded, onFragmentPreRemoved, onFragmentMaxLifecyclePreUpdated called after the operation ends.

Public constructors

FragmentStateAdapter(
    fragmentManager: FragmentManager,
    lifecycle: Lifecycle
)

Public functions

Boolean
containsItem(itemId: Long)

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

abstract Fragment
createFragment(position: Int)

Provide a new Fragment associated with the specified position.

Long
getItemId(position: Int)

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

Unit

Called by RecyclerView when it starts observing this Adapter.

Unit
onBindViewHolder(holder: FragmentViewHolder, position: Int)

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

FragmentViewHolder
onCreateViewHolder(parent: ViewGroup, viewType: Int)

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

Unit

Called by RecyclerView when it stops observing this Adapter.

Boolean

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

Unit

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

Unit

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

Unit

Registers a FragmentTransactionCallback to listen to fragment lifecycle changes that happen inside the adapter.

Unit
restoreState(savedState: Parcelable)

Restores adapter state

Parcelable

Saves adapter state

Unit
setHasStableIds(hasStableIds: Boolean)

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

Unit

Unregisters a FragmentTransactionCallback.

Inherited functions

From androidx.recyclerview.widget.RecyclerView.Adapter
Unit
bindViewHolder(holder: VH, position: Int)

This method internally calls onBindViewHolder to update the ViewHolder contents with the item at the given position and also sets up some private fields to be used by RecyclerView.

VH
createViewHolder(parent: ViewGroup, viewType: Int)

This method calls onCreateViewHolder to create a new ViewHolder and initializes some private fields to be used by RecyclerView.

Int
findRelativeAdapterPositionIn(
    adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>,
    viewHolder: RecyclerView.ViewHolder,
    localPosition: Int
)

Returns the position of the given ViewHolder in the given Adapter.

abstract Int

Returns the total number of items in the data set held by the adapter.

Int
getItemViewType(position: Int)

Return the view type of the item at position for the purposes of view recycling.

RecyclerView.Adapter.StateRestorationPolicy

Returns when this Adapter wants to restore the state.

Boolean

Returns true if one or more observers are attached to this adapter.

Boolean

Returns true if this adapter publishes a unique long value that can act as a key for the item at a given position in the data set.

Unit

Notify any registered observers that the data set has changed.

Unit

Notify any registered observers that the item at position has changed.

Unit
notifyItemChanged(position: Int, payload: Any?)

Notify any registered observers that the item at position has changed with an optional payload object.

Unit

Notify any registered observers that the item reflected at position has been newly inserted.

Unit
notifyItemMoved(fromPosition: Int, toPosition: Int)

Notify any registered observers that the item reflected at fromPosition has been moved to toPosition.

Unit
notifyItemRangeChanged(positionStart: Int, itemCount: Int)

Notify any registered observers that the itemCount items starting at position positionStart have changed.

Unit
notifyItemRangeChanged(positionStart: Int, itemCount: Int, payload: Any?)

Notify any registered observers that the itemCount items starting at position positionStart have changed.

Unit
notifyItemRangeInserted(positionStart: Int, itemCount: Int)

Notify any registered observers that the currently reflected itemCount items starting at positionStart have been newly inserted.

Unit
notifyItemRangeRemoved(positionStart: Int, itemCount: Int)

Notify any registered observers that the itemCount items previously located at positionStart have been removed from the data set.

Unit

Notify any registered observers that the item previously located at position has been removed from the data set.

Unit
onBindViewHolder(holder: VH, position: Int, payloads: (Mutable)List<Any!>)

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

Unit

Called when a view created by this adapter has been detached from its window.

Unit

Register a new observer to listen for data changes.

Unit

Sets the state restoration strategy for the Adapter.

Unit

Unregister an observer currently listening for data changes.

Public constructors

FragmentStateAdapter

Added in 1.0.0
FragmentStateAdapter(fragmentActivity: FragmentActivity)
Parameters
fragmentActivity: FragmentActivity

if the ViewPager2 lives directly in a FragmentActivity subclass.

FragmentStateAdapter

Added in 1.0.0
FragmentStateAdapter(fragment: Fragment)
Parameters
fragment: Fragment

if the ViewPager2 lives directly in a Fragment subclass.

FragmentStateAdapter

Added in 1.0.0
FragmentStateAdapter(
    fragmentManager: FragmentManager,
    lifecycle: Lifecycle
)
Parameters
fragmentManager: FragmentManager

of ViewPager2's host

lifecycle: Lifecycle

of ViewPager2's host

Public functions

containsItem

Added in 1.0.0
fun containsItem(itemId: Long): Boolean

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

When overriding, also override getItemId

createFragment

Added in 1.0.0
abstract fun createFragment(position: Int): Fragment

Provide a new Fragment associated with the specified position.

The adapter will be responsible for the Fragment lifecycle:

  • The Fragment will be used to display an item.
  • The Fragment will be destroyed when it gets too far from the viewport, and its state will be saved. When the item is close to the viewport again, a new Fragment will be requested, and a previously saved state will be used to initialize it.

getItemId

fun getItemId(position: Int): Long

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

When overriding, also override containsItem.

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

Parameters
position: Int

Adapter position

Returns
Long

stable item id hasStableIds

onAttachedToRecyclerView

@CallSuper
fun onAttachedToRecyclerView(recyclerView: RecyclerView): Unit

Called by RecyclerView when it starts observing this Adapter.

Keep in mind that same adapter may be observed by multiple RecyclerViews.

Parameters
recyclerView: RecyclerView

The RecyclerView instance which started observing this adapter.

onBindViewHolder

Added in 1.0.0
fun onBindViewHolder(holder: FragmentViewHolder, position: Int): Unit

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

Note that unlike android.widget.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 getBindingAdapterPosition which will have the updated adapter position. Override onBindViewHolder 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

Added in 1.0.0
fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FragmentViewHolder

Called when RecyclerView needs a new 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. 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 findViewById 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.

onDetachedFromRecyclerView

@CallSuper
fun onDetachedFromRecyclerView(recyclerView: RecyclerView): Unit

Called by RecyclerView when it stops observing this Adapter.

Parameters
recyclerView: RecyclerView

The RecyclerView instance which stopped observing this adapter.

onFailedToRecycleView

Added in 1.0.0
fun onFailedToRecycleView(holder: FragmentViewHolder): Boolean

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 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 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

Added in 1.0.0
fun onViewAttachedToWindow(holder: FragmentViewHolder): Unit

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

Added in 1.0.0
fun onViewRecycled(holder: FragmentViewHolder): Unit

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

A view is recycled when a 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 getBindingAdapterPosition to get its adapter position.

Parameters
holder: FragmentViewHolder

The ViewHolder for the view being recycled

registerFragmentTransactionCallback

Added in 1.1.0
fun registerFragmentTransactionCallback(
    callback: FragmentStateAdapter.FragmentTransactionCallback
): Unit

Registers a FragmentTransactionCallback to listen to fragment lifecycle changes that happen inside the adapter.

Parameters
callback: FragmentStateAdapter.FragmentTransactionCallback

Callback to register

restoreState

Added in 1.1.0
fun restoreState(savedState: Parcelable): Unit

Restores adapter state

saveState

Added in 1.1.0
fun saveState(): Parcelable

Saves adapter state

setHasStableIds

Added in 1.0.0
fun setHasStableIds(hasStableIds: Boolean): Unit

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

Parameters
hasStableIds: Boolean

Whether items in data set have unique identifiers or not.

unregisterFragmentTransactionCallback

Added in 1.1.0
fun unregisterFragmentTransactionCallback(
    callback: FragmentStateAdapter.FragmentTransactionCallback
): Unit

Unregisters a FragmentTransactionCallback.

Parameters
callback: FragmentStateAdapter.FragmentTransactionCallback

Callback to unregister