ConcatAdapter

Artifact: androidx.recyclerview:recyclerview

Added in 1.2.0

Kotlin |Java

class ConcatAdapter : RecyclerView.Adapter

kotlin.Any
↳	androidx.recyclerview.widget.RecyclerView.Adapter
	↳	androidx.recyclerview.widget.ConcatAdapter

An Adapter implementation that presents the contents of multiple adapters in sequence.

MyAdapter adapter1 = ...;
AnotherAdapter adapter2 = ...;
ConcatAdapter concatenated = new ConcatAdapter(adapter1, adapter2);
recyclerView.setAdapter(concatenated);

By default, ConcatAdapter isolates view types of nested adapters from each other such that it will change the view type before reporting it back to the RecyclerView to avoid any conflicts between the view types of added adapters. This also means each added adapter will have its own isolated pool of ViewHolders, with no re-use in between added adapters.

If your Adapters share the same view types, and can support sharing ViewHolder s between added adapters, provide an instance of Config where you set isolateViewTypes to false. A common usage pattern for this is to return the R.layout.<layout_name> from the getItemViewType method.

When an added adapter calls one of the notify methods, ConcatAdapter properly offsets values before reporting it back to the RecyclerView. If an adapter calls notifyDataSetChanged, ConcatAdapter also calls notifyDataSetChanged as calling notifyItemRangeChanged will confuse the RecyclerView. You are highly encouraged to to use SortedList or ListAdapter to avoid calling notifyDataSetChanged.

Whether ConcatAdapter should support stable ids is defined in the Config object. Calling setHasStableIds has no effect. See documentation for Config.StableIdMode for details on how to configure ConcatAdapter to use stable ids. By default, it will not use stable ids and sub adapter stable ids will be ignored. Similar to the case above, you are highly encouraged to use ListAdapter, which will automatically calculate the changes in the data set for you so you won't need stable ids.

It is common to find the adapter position of a ViewHolder to handle user action on the ViewHolder. For those cases, instead of calling getAdapterPosition, use getBindingAdapterPosition. If your adapters share ViewHolders, you can use the getBindingAdapter method to find the adapter which last bound that ViewHolder.

Summary

Nested types
`class ConcatAdapter.Config` The configuration object for a `ConcatAdapter`.
`class ConcatAdapter.Config.Builder` The builder for `Config` class.
`enum ConcatAdapter.Config.StableIdMode` Defines how `ConcatAdapter` handle stable ids (`hasStableIds`).

Public constructors
`@SafeVarargs ConcatAdapter( adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!> )` Creates a ConcatAdapter with `DEFAULT` and the given adapters in the given order.
`ConcatAdapter( adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!> )` Creates a ConcatAdapter with `DEFAULT` and the given adapters in the given order.
`@SafeVarargs ConcatAdapter( config: ConcatAdapter.Config, adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!> )` Creates a ConcatAdapter with the given config and the given adapters in the given order.
`ConcatAdapter( config: ConcatAdapter.Config, adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!> )` Creates a ConcatAdapter with the given config and the given adapters in the given order.

Public functions
`Boolean`	`addAdapter(adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>)` Appends the given adapter to the existing list of adapters and notifies the observers of this `ConcatAdapter`.
`Boolean`	`addAdapter( index: Int, adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!> )` Adds the given adapter to the given index among other adapters that are already added.
`Int`	`findRelativeAdapterPositionIn( adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>, viewHolder: RecyclerView.ViewHolder, localPosition: Int )` Returns the position of the given `ViewHolder` in the given `Adapter`.
`(Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	`getAdapters()` Returns an unmodifiable copy of the list of adapters in this `ConcatAdapter`.
`Int`	`getItemCount()` Returns the total number of items in the data set held by the adapter.
`Long`	`getItemId(position: Int)` Return the stable ID for the item at `position`.
`Int`	`getItemViewType(position: Int)` Return the view type of the item at `position` for the purposes of view recycling.
`Pair<RecyclerView.Adapter<RecyclerView.ViewHolder!>!, Int!>`	`getWrappedAdapterAndPosition(globalPosition: Int)` Retrieve the adapter and local position for a given position in this `ConcatAdapter`.
`Unit`	`onAttachedToRecyclerView(recyclerView: RecyclerView)` Called by RecyclerView when it starts observing this Adapter.
`Unit`	`onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int)` Called by RecyclerView to display the data at the specified position.
`RecyclerView.ViewHolder`	`onCreateViewHolder(parent: ViewGroup, viewType: Int)` Called when RecyclerView needs a new `ViewHolder` of the given type to represent an item.
`Unit`	`onDetachedFromRecyclerView(recyclerView: RecyclerView)` Called by RecyclerView when it stops observing this Adapter.
`Boolean`	`onFailedToRecycleView(holder: RecyclerView.ViewHolder)` Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state.
`Unit`	`onViewAttachedToWindow(holder: RecyclerView.ViewHolder)` Called when a view created by this adapter has been attached to a window.
`Unit`	`onViewDetachedFromWindow(holder: RecyclerView.ViewHolder)` Called when a view created by this adapter has been detached from its window.
`Unit`	`onViewRecycled(holder: RecyclerView.ViewHolder)` Called when a view created by this adapter has been recycled.
`Boolean`	`removeAdapter(adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>)` Removes the given adapter from the adapters list if it exists
`Unit`	`setHasStableIds(hasStableIds: Boolean)` Calling this method is an error and will result in an `UnsupportedOperationException`.
`Unit`	`setStateRestorationPolicy( strategy: RecyclerView.Adapter.StateRestorationPolicy )` Calling this method is an error and will result in an `UnsupportedOperationException`.

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.
`RecyclerView.Adapter.StateRestorationPolicy`	`getStateRestorationPolicy()` Returns when this Adapter wants to restore the state.
`Boolean`	`hasObservers()` Returns true if one or more observers are attached to this adapter.
`Boolean`	`hasStableIds()` 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`	`notifyDataSetChanged()` Notify any registered observers that the data set has changed.
`Unit`	`notifyItemChanged(position: Int)` 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`	`notifyItemInserted(position: Int)` 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`	`notifyItemRemoved(position: Int)` 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`	`registerAdapterDataObserver(observer: RecyclerView.AdapterDataObserver)` Register a new observer to listen for data changes.
`Unit`	`unregisterAdapterDataObserver( observer: RecyclerView.AdapterDataObserver )` Unregister an observer currently listening for data changes.

Public constructors

@SafeVarargs
ConcatAdapter(
    adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>
)

Creates a ConcatAdapter with DEFAULT and the given adapters in the given order.

Parameters
`adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	The list of adapters to add

Added in 1.2.0

ConcatAdapter(
    adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>
)

Creates a ConcatAdapter with DEFAULT and the given adapters in the given order.

Parameters
`adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	The list of adapters to add

@SafeVarargs
ConcatAdapter(
    config: ConcatAdapter.Config,
    adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>
)

Creates a ConcatAdapter with the given config and the given adapters in the given order.

Parameters
`config: ConcatAdapter.Config`	The configuration for this ConcatAdapter
`adapters: Array<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	The list of adapters to add

See also
`ConcatAdapter.Config.Builder`

Added in 1.2.0

ConcatAdapter(
    config: ConcatAdapter.Config,
    adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>
)

Creates a ConcatAdapter with the given config and the given adapters in the given order.

Parameters
`config: ConcatAdapter.Config`	The configuration for this ConcatAdapter
`adapters: (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	The list of adapters to add

See also
`ConcatAdapter.Config.Builder`

Public functions

Added in 1.2.0

fun addAdapter(adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>): Boolean

Appends the given adapter to the existing list of adapters and notifies the observers of this ConcatAdapter.

Parameters
`adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>`	The new adapter to add

Returns
`Boolean`	`true` if the adapter is successfully added because it did not already exist, `false` otherwise.

See also
`addAdapter`
`removeAdapter`

Added in 1.2.0

fun addAdapter(
    index: Int,
    adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>
): Boolean

Adds the given adapter to the given index among other adapters that are already added.

Parameters
`index: Int`	The index into which to insert the adapter. ConcatAdapter will throw an `IndexOutOfBoundsException` if the index is not between 0 and current adapter count (inclusive).
`adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>`	The new adapter to add to the adapters list.

Returns
`Boolean`	`true` if the adapter is successfully added because it did not already exist, `false` otherwise.

See also
`addAdapter`
`removeAdapter`

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

Returns the position of the given ViewHolder in the given Adapter. If the given Adapter is not part of this ConcatAdapter, NO_POSITION is returned.

Parameters
`adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>`	The adapter which is a sub adapter of this ConcatAdapter or itself.
`viewHolder: RecyclerView.ViewHolder`	The view holder whose local position in the given adapter will be returned.
`localPosition: Int`	The position of the given `ViewHolder` in this `Adapter`.

Returns
`Int`	The local position of the given `ViewHolder` in the given `Adapter` or `NO_POSITION` if the `ViewHolder` is not bound to an item or the given `Adapter` is not part of this ConcatAdapter.

getAdapters

Added in 1.2.0

fun getAdapters(): (Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>

Returns an unmodifiable copy of the list of adapters in this ConcatAdapter. Note that this is a copy hence future changes in the ConcatAdapter are not reflected in this list.

Returns
`(Mutable)List<RecyclerView.Adapter<RecyclerView.ViewHolder!>!>`	A copy of the list of adapters in this ConcatAdapter.

getItemCount

Added in 1.4.0

fun getItemCount(): Int

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

Returns
`Int`	The total number of items in this adapter.

getItemId

fun getItemId(position: Int): Long

Return the stable ID for the item at position. If hasStableIds would return false this method should return NO_ID. The default implementation of this method returns NO_ID.

Parameters
`position: Int`	Adapter position to query

Returns
`Long`	the stable ID of the item at position

getItemViewType

fun getItemViewType(position: Int): Int

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

The default implementation of this method returns 0, making the assumption of a single view type for the adapter. Unlike ListView adapters, types need not be contiguous. Consider using id resources to uniquely identify item view types.

Parameters
`position: Int`	position to query

Returns
`Int`	integer value identifying the type of the view needed to represent the item at `position`. Type codes need not be contiguous.

getWrappedAdapterAndPosition

Added in 1.3.0

fun getWrappedAdapterAndPosition(globalPosition: Int): Pair<RecyclerView.Adapter<RecyclerView.ViewHolder!>!, Int!>

Retrieve the adapter and local position for a given position in this ConcatAdapter. This allows for retrieving wrapped adapter information in situations where you don't have a ViewHolder, such as within a androidx.recyclerview.widget.GridLayoutManager.SpanSizeLookup in which you want to look up information from the source adapter.

Parameters
`globalPosition: Int`	The position in this `ConcatAdapter`.

Returns
`Pair<RecyclerView.Adapter<RecyclerView.ViewHolder!>!, Int!>`	a Pair with the first element set to the wrapped `Adapter` containing that position and the second element set to the local position in the wrapped adapter

Throws
`java.lang.IllegalArgumentException`	if the specified `globalPosition` does not correspond to a valid element of this adapter. That is, if `globalPosition` is less than 0 or greater than the total number of items in the `ConcatAdapter`

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.

See also
`onDetachedFromRecyclerView`

Added in 1.2.0

fun onBindViewHolder(holder: RecyclerView.ViewHolder, 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: RecyclerView.ViewHolder`	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 1.4.0

fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder

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
`RecyclerView.ViewHolder`	A new ViewHolder that holds a View of the given view type.

See also
`getItemViewType`
`onBindViewHolder`

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.

See also
`onAttachedToRecyclerView`

Added in 1.2.0

fun onFailedToRecycleView(holder: RecyclerView.ViewHolder): 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: RecyclerView.ViewHolder`	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.

Added in 1.2.0

fun onViewAttachedToWindow(holder: RecyclerView.ViewHolder): 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: RecyclerView.ViewHolder`	Holder of the view being attached

Added in 1.2.0

fun onViewDetachedFromWindow(holder: RecyclerView.ViewHolder): Unit

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

Becoming detached from the window is not necessarily a permanent condition; the consumer of an Adapter's views may choose to cache views offscreen while they are not visible, attaching and detaching them as appropriate.

Parameters
`holder: RecyclerView.ViewHolder`	Holder of the view being detached

Added in 1.2.0

fun onViewRecycled(holder: RecyclerView.ViewHolder): 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: RecyclerView.ViewHolder`	The ViewHolder for the view being recycled

Added in 1.2.0

fun removeAdapter(adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>): Boolean

Removes the given adapter from the adapters list if it exists

Parameters
`adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>`	The adapter to remove

Returns
`Boolean`	`true` if the adapter was previously added to this `ConcatAdapter` and now removed or `false` if it couldn't be found.

setHasStableIds

fun setHasStableIds(hasStableIds: Boolean): Unit

Calling this method is an error and will result in an UnsupportedOperationException. You should use the Config object passed into the ConcatAdapter to configure this behavior.

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

fun setStateRestorationPolicy(
    strategy: RecyclerView.Adapter.StateRestorationPolicy
): Unit

Calling this method is an error and will result in an UnsupportedOperationException. ConcatAdapter infers this value from added Adapters.

Parameters
`strategy: RecyclerView.Adapter.StateRestorationPolicy`	The saved state restoration strategy for this Adapter such that `ConcatAdapter` will allow state restoration only if all added adapters allow it or there are no adapters.

ConcatAdapter

Summary

Nested types

Public constructors

Public functions

Inherited functions

Public constructors

ConcatAdapter

ConcatAdapter

ConcatAdapter

ConcatAdapter

Public functions

addAdapter

addAdapter

findRelativeAdapterPositionIn

getAdapters

getItemCount

getItemId

getItemViewType

getWrappedAdapterAndPosition

onAttachedToRecyclerView

onBindViewHolder

onCreateViewHolder

onDetachedFromRecyclerView

onFailedToRecycleView

onViewAttachedToWindow

onViewDetachedFromWindow

onViewRecycled

removeAdapter

setHasStableIds

setStateRestorationPolicy