RecyclerView

Kotlin |Java

open class RecyclerView : ViewGroup, ScrollingView, NestedScrollingChild2, NestedScrollingChild3

kotlin.Any
↳	android.view.View
	↳	android.view.ViewGroup
		↳	androidx.recyclerview.widget.RecyclerView

Known Direct Subclasses

BaseGridView, WearableRecyclerView

BaseGridView	An abstract base class for vertically and horizontally scrolling lists.
WearableRecyclerView	Wearable specific implementation of the `RecyclerView` enabling circular scrolling} and semi-circular layouts.

Known Indirect Subclasses

HorizontalGridView, VerticalGridView

HorizontalGridView	A `android.view.ViewGroup` that shows items in a horizontal scrolling list.
VerticalGridView	A `android.view.ViewGroup` that shows items in a vertically scrolling list.

A flexible view for providing a limited window into a large data set.

Glossary of terms:

Adapter: A subclass of Adapter responsible for providing views that represent items in a data set.
Position: The position of a data item within an Adapter.
Index: The index of an attached child view as used in a call to ViewGroup#getChildAt. Contrast with Position.
Binding: The process of preparing a child view to display data corresponding to a position within the adapter.
Recycle (view): A view previously used to display data for a specific adapter position may be placed in a cache for later reuse to display the same type of data again later. This can drastically improve performance by skipping initial layout inflation or construction.
Scrap (view): A child view that has entered into a temporarily detached state during layout. Scrap views may be reused without becoming fully detached from the parent RecyclerView, either unmodified if no rebinding is required or modified by the adapter if the view was considered dirty.
Dirty (view): A child view that must be rebound by the adapter before being displayed.

Positions in RecyclerView:

RecyclerView introduces an additional level of abstraction between the Adapter and LayoutManager to be able to detect data set changes in batches during a layout calculation. This saves LayoutManager from tracking adapter changes to calculate animations. It also helps with performance because all view bindings happen at the same time and unnecessary bindings are avoided.

For this reason, there are two types of position related methods in RecyclerView:

layout position: Position of an item in the latest layout calculation. This is the position from the LayoutManager's perspective.
adapter position: Position of an item in the adapter. This is the position from the Adapter's perspective.

These two positions are the same except the time between dispatching adapter.notify* events and calculating the updated layout.

Methods that return or receive *LayoutPosition* use position as of the latest layout calculation (e.g. ViewHolder#getLayoutPosition(), findViewHolderForLayoutPosition(int)). These positions include all changes until the last layout calculation. You can rely on these positions to be consistent with what user is currently seeing on the screen. For example, if you have a list of items on the screen and user asks for the 5th element, you should use these methods as they'll match what user is seeing.

The other set of position related methods are in the form of *AdapterPosition*. (e.g. ViewHolder#getAbsoluteAdapterPosition(), ViewHolder#getBindingAdapterPosition(), findViewHolderForAdapterPosition(int)) You should use these methods when you need to work with up-to-date adapter positions even if they may not have been reflected to layout yet. For example, if you want to access the item in the adapter on a ViewHolder click, you should use ViewHolder#getBindingAdapterPosition(). Beware that these methods may not be able to calculate adapter positions if Adapter#notifyDataSetChanged() has been called and new layout has not yet been calculated. For this reasons, you should carefully handle NO_POSITION or null results from these methods.

When writing a LayoutManager you almost always want to use layout positions whereas when writing an Adapter, you probably want to use adapter positions.

Presenting Dynamic Data

To display updatable data in a RecyclerView, your adapter needs to signal inserts, moves, and deletions to RecyclerView. You can build this yourself by manually calling adapter.notify* methods when content changes, or you can use one of the easier solutions RecyclerView provides:

List diffing with DiffUtil

If your RecyclerView is displaying a list that is re-fetched from scratch for each update (e.g. from the network, or from a database), DiffUtil can calculate the difference between versions of the list. DiffUtil takes both lists as input and computes the difference, which can be passed to RecyclerView to trigger minimal animations and updates to keep your UI performant, and animations meaningful. This approach requires that each list is represented in memory with immutable content, and relies on receiving updates as new instances of lists. This approach is also ideal if your UI layer doesn't implement sorting, it just presents the data in the order it's given.

The best part of this approach is that it extends to any arbitrary changes - item updates, moves, addition and removal can all be computed and handled the same way. Though you do have to keep two copies of the list in memory while diffing, and must avoid mutating them, it's possible to share unmodified elements between list versions.

There are three primary ways to do this for RecyclerView. We recommend you start with ListAdapter, the higher-level API that builds in List diffing on a background thread, with minimal code. AsyncListDiffer also provides this behavior, but without defining an Adapter to subclass. If you want more control, DiffUtil is the lower-level API you can use to compute the diffs yourself. Each approach allows you to specify how diffs should be computed based on item data.

List mutation with SortedList

If your RecyclerView receives updates incrementally, e.g. item X is inserted, or item Y is removed, you can use SortedList to manage your list. You define how to order items, and it will automatically trigger update signals that RecyclerView can use. SortedList works if you only need to handle insert and remove events, and has the benefit that you only ever need to have a single copy of the list in memory. It can also compute differences with SortedList#replaceAll(Object[]), but this method is more limited than the list diffing behavior above.

Paging Library

The Paging library extends the diff-based approach to additionally support paged loading. It provides the androidx.paging.PagedList class that operates as a self-loading list, provided a source of data like a database, or paginated network API. It provides convenient list diffing support out of the box, similar to ListAdapter and AsyncListDiffer. For more information about the Paging library, see the library documentation. androidx.recyclerview.R.attr#layoutManager

Summary

Nested classes
abstract	`Adapter` Base class for an Adapter
abstract	`AdapterDataObserver` Observer base class for watching changes to an `Adapter`.
abstract	`ChildDrawingOrderCallback` A callback interface that can be used to alter the drawing order of RecyclerView children.
open	`EdgeEffectFactory` EdgeEffectFactory lets you customize the over-scroll edge effect for RecyclerViews.
abstract	`ItemAnimator` This class defines the animations that take place on items as changes are made to the adapter.
abstract	`ItemDecoration` An ItemDecoration allows the application to add a special drawing and layout offset to specific item views from the adapter's data set.
abstract	`LayoutManager` A `LayoutManager` is responsible for measuring and positioning item views within a `RecyclerView` as well as determining the policy for when to recycle item views that are no longer visible to the user.
open	`LayoutParams` `LayoutParams` subclass for children of `RecyclerView`.
abstract	`OnChildAttachStateChangeListener` A Listener interface that can be attached to a RecylcerView to get notified whenever a ViewHolder is attached to or detached from RecyclerView.
abstract	`OnFlingListener` This class defines the behavior of fling if the developer wishes to handle it.
abstract	`OnItemTouchListener` An OnItemTouchListener allows the application to intercept touch events in progress at the view hierarchy level of the RecyclerView before those touch events are considered for RecyclerView's own scrolling behavior.
abstract	`OnScrollListener` An OnScrollListener can be added to a RecyclerView to receive messages when a scrolling event has occurred on that RecyclerView.
open	`RecycledViewPool` RecycledViewPool lets you share Views between multiple RecyclerViews.
	`Recycler` A Recycler is responsible for managing scrapped or detached item views for reuse.
abstract	`RecyclerListener` A RecyclerListener can be set on a RecyclerView to receive messages whenever a view is recycled.
open	`SimpleOnItemTouchListener` An implementation of `RecyclerView.OnItemTouchListener` that has empty method bodies and default return values.
abstract	`SmoothScroller` Base class for smooth scrolling.
open	`State` Contains useful information about the current RecyclerView state like target scroll position or view focus.
abstract	`ViewCacheExtension` ViewCacheExtension is a helper class to provide an additional layer of view caching that can be controlled by the developer.
abstract	`ViewHolder` A ViewHolder describes an item view and metadata about its place within the RecyclerView.

Constants
static Int	`HORIZONTAL`
static Int	`INVALID_TYPE`
static Long	`NO_ID`
static Int	`NO_POSITION`
static Int	`SCROLL_STATE_DRAGGING` The RecyclerView is currently being dragged by outside input such as user touch input.
static Int	`SCROLL_STATE_IDLE` The RecyclerView is not currently scrolling.
static Int	`SCROLL_STATE_SETTLING` The RecyclerView is currently animating to a final position while not under outside control.
static Int	`TOUCH_SLOP_DEFAULT` Constant for use with `setScrollingTouchSlop(int)`.
static Int	`TOUCH_SLOP_PAGING` Constant for use with `setScrollingTouchSlop(int)`.
static Int	`UNDEFINED_DURATION` Constant that represents that a duration has not been defined.
static Int	`VERTICAL`

Public constructors
`<init>(@NonNull context: Context)`
`<init>(@NonNull context: Context, @Nullable attrs: AttributeSet?)`
`<init>(@NonNull context: Context, @Nullable attrs: AttributeSet?, defStyleAttr: Int)`

Public methods
open Unit	`addFocusables(views: ArrayList<View!>!, direction: Int, focusableMode: Int)`
open Unit	`addItemDecoration(@NonNull decor: RecyclerView.ItemDecoration, index: Int)` Add an `ItemDecoration` to this RecyclerView.
open Unit	`addItemDecoration(@NonNull decor: RecyclerView.ItemDecoration)` Add an `ItemDecoration` to this RecyclerView.
open Unit	`addOnChildAttachStateChangeListener(@NonNull listener: RecyclerView.OnChildAttachStateChangeListener)` Register a listener that will be notified whenever a child view is attached to or detached from RecyclerView.
open Unit	`addOnItemTouchListener(@NonNull listener: RecyclerView.OnItemTouchListener)` Add an `OnItemTouchListener` to intercept touch events before they are dispatched to child views or this view's standard scrolling behavior.
open Unit	`addOnScrollListener(@NonNull listener: RecyclerView.OnScrollListener)` Add a listener that will be notified of any changes in scroll state or position.
open Unit	`clearOnChildAttachStateChangeListeners()` Removes all listeners that were added via `addOnChildAttachStateChangeListener(OnChildAttachStateChangeListener)`.
open Unit	`clearOnScrollListeners()` Remove all secondary listener that were notified of any changes in scroll state or position.
open Int	`computeHorizontalScrollExtent()` Compute the horizontal extent of the horizontal scrollbar's thumb within the horizontal range.
open Int	`computeHorizontalScrollOffset()` Compute the horizontal offset of the horizontal scrollbar's thumb within the horizontal range.
open Int	`computeHorizontalScrollRange()` Compute the horizontal range that the horizontal scrollbar represents.
open Int	`computeVerticalScrollExtent()` Compute the vertical extent of the vertical scrollbar's thumb within the vertical range.
open Int	`computeVerticalScrollOffset()` Compute the vertical offset of the vertical scrollbar's thumb within the vertical range.
open Int	`computeVerticalScrollRange()` Compute the vertical range that the vertical scrollbar represents.
open Boolean	`dispatchNestedFling(velocityX: Float, velocityY: Float, consumed: Boolean)`
open Boolean	`dispatchNestedPreFling(velocityX: Float, velocityY: Float)`
open Boolean	`dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?)`
open Boolean	`dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?, type: Int)`
open Boolean	`dispatchNestedScroll(dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int, offsetInWindow: IntArray?)`
open Boolean	`dispatchNestedScroll(dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int, offsetInWindow: IntArray?, type: Int)`
Unit	`dispatchNestedScroll(dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int, offsetInWindow: IntArray?, type: Int, @NonNull consumed: IntArray)`
open Boolean	`dispatchPopulateAccessibilityEvent(event: AccessibilityEvent!)`
open Unit	`draw(c: Canvas!)`
open Boolean	`drawChild(canvas: Canvas!, child: View!, drawingTime: Long)`
open View?	`findChildViewUnder(x: Float, y: Float)` Find the topmost view under the given point.
open View?	`findContainingItemView(@NonNull view: View)` Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the RecyclerView.
open RecyclerView.ViewHolder?	`findContainingViewHolder(@NonNull view: View)` Returns the ViewHolder that contains the given view.
open RecyclerView.ViewHolder?	`findViewHolderForAdapterPosition(position: Int)` Return the ViewHolder for the item in the given position of the data set.
open RecyclerView.ViewHolder!	`findViewHolderForItemId(id: Long)` Return the ViewHolder for the item with the given id.
open RecyclerView.ViewHolder?	`findViewHolderForLayoutPosition(position: Int)` Return the ViewHolder for the item in the given position of the data set as of the latest layout pass.
open RecyclerView.ViewHolder?	`findViewHolderForPosition(position: Int)`
open Boolean	`fling(velocityX: Int, velocityY: Int)` Begin a standard fling with an initial velocity along each axis in pixels per second.
open View!	`focusSearch(focused: View!, direction: Int)` Since RecyclerView is a collection ViewGroup that includes virtual children (items that are in the Adapter but not visible in the UI), it employs a more involved focus search strategy that differs from other ViewGroups.
open LayoutParams!	`generateLayoutParams(attrs: AttributeSet!)`
open CharSequence!	`getAccessibilityClassName()`
open RecyclerView.Adapter<RecyclerView.ViewHolder!>?	`getAdapter()` Retrieves the previously set adapter or null if no adapter is set.
open Int	`getBaseline()` Return the offset of the RecyclerView's text baseline from the its top boundary.
open Int	`getChildAdapterPosition(@NonNull child: View)` Return the adapter position that the given child view corresponds to.
open Long	`getChildItemId(@NonNull child: View)` Return the stable item id that the given child view corresponds to.
open Int	`getChildLayoutPosition(@NonNull child: View)` Return the adapter position of the given child view as of the latest completed layout pass.
open Int	`getChildPosition(@NonNull child: View)`
open RecyclerView.ViewHolder!	`getChildViewHolder(@NonNull child: View)` Retrieve the `ViewHolder` for the given child view.
open Boolean	`getClipToPadding()` Returns whether this RecyclerView will clip its children to its padding, and resize (but not clip) any EdgeEffect to the padded region, if padding is present.
open RecyclerViewAccessibilityDelegate?	`getCompatAccessibilityDelegate()` Returns the accessibility delegate compatibility implementation used by the RecyclerView.
open Unit	`getDecoratedBoundsWithMargins(@NonNull view: View, @NonNull outBounds: Rect)` Returns the bounds of the view including its decoration and margins.
open RecyclerView.EdgeEffectFactory	`getEdgeEffectFactory()` Retrieves the previously set `EdgeEffectFactory` or the default factory if nothing was set.
open RecyclerView.ItemAnimator?	`getItemAnimator()` Gets the current ItemAnimator for this RecyclerView.
open RecyclerView.ItemDecoration	`getItemDecorationAt(index: Int)` Returns an `ItemDecoration` previously added to this RecyclerView.
open Int	`getItemDecorationCount()` Returns the number of `ItemDecoration` currently added to this RecyclerView.
open RecyclerView.LayoutManager?	`getLayoutManager()` Return the `LayoutManager` currently responsible for layout policy for this RecyclerView.
open Int	`getMaxFlingVelocity()` Returns the maximum fling velocity used by this RecyclerView.
open Int	`getMinFlingVelocity()` Returns the minimum velocity to start a fling.
open RecyclerView.OnFlingListener?	`getOnFlingListener()` Get the current `OnFlingListener` from this `RecyclerView`.
open Boolean	`getPreserveFocusAfterLayout()` Returns true if the RecyclerView should attempt to preserve currently focused Adapter Item's focus even if the View representing the Item is replaced during a layout calculation.
open RecyclerView.RecycledViewPool	`getRecycledViewPool()` Retrieve this RecyclerView's `RecycledViewPool`.
open Int	`getScrollState()` Return the current scrolling state of the RecyclerView.
open Boolean	`hasFixedSize()`
open Boolean	`hasNestedScrollingParent()`
open Boolean	`hasNestedScrollingParent(type: Int)`
open Boolean	`hasPendingAdapterUpdates()` Returns whether there are pending adapter updates which are not yet applied to the layout.
open Unit	`invalidateItemDecorations()` Invalidates all ItemDecorations.
open Boolean	`isAnimating()` Returns true if RecyclerView is currently running some animations.
open Boolean	`isAttachedToWindow()` Returns true if RecyclerView is attached to window.
open Boolean	`isComputingLayout()` Returns whether RecyclerView is currently computing a layout.
open Boolean	`isLayoutFrozen()`
Boolean	`isLayoutSuppressed()` Returns whether layout and scroll calls on this container are currently being suppressed, due to an earlier call to `suppressLayout(boolean)`.
open Boolean	`isNestedScrollingEnabled()`
open Unit	`nestedScrollBy(x: Int, y: Int)` Same as `RecyclerView#scrollBy(int, int)`, but also participates in nested scrolling.
open Unit	`offsetChildrenHorizontal(@Px dx: Int)` Offset the bounds of all child views by `dx` pixels.
open Unit	`offsetChildrenVertical(@Px dy: Int)` Offset the bounds of all child views by `dy` pixels.
open Unit	`onChildAttachedToWindow(@NonNull child: View)` Called when an item view is attached to this RecyclerView.
open Unit	`onChildDetachedFromWindow(@NonNull child: View)` Called when an item view is detached from this RecyclerView.
open Unit	`onDraw(c: Canvas!)`
open Boolean	`onGenericMotionEvent(event: MotionEvent!)`
open Boolean	`onInterceptTouchEvent(e: MotionEvent!)`
open Unit	`onScrollStateChanged(state: Int)` Called when the scroll state of this RecyclerView changes.
open Unit	`onScrolled(@Px dx: Int, @Px dy: Int)` Called when the scroll position of this RecyclerView changes.
open Boolean	`onTouchEvent(e: MotionEvent!)`
open Unit	`removeItemDecoration(@NonNull decor: RecyclerView.ItemDecoration)` Remove an `ItemDecoration` from this RecyclerView.
open Unit	`removeItemDecorationAt(index: Int)` Removes the `ItemDecoration` associated with the supplied index position.
open Unit	`removeOnChildAttachStateChangeListener(@NonNull listener: RecyclerView.OnChildAttachStateChangeListener)` Removes the provided listener from child attached state listeners list.
open Unit	`removeOnItemTouchListener(@NonNull listener: RecyclerView.OnItemTouchListener)` Remove an `OnItemTouchListener`.
open Unit	`removeOnScrollListener(@NonNull listener: RecyclerView.OnScrollListener)` Remove a listener that was notified of any changes in scroll state or position.
open Unit	`requestChildFocus(child: View!, focused: View!)`
open Boolean	`requestChildRectangleOnScreen(child: View!, rect: Rect!, immediate: Boolean)`
open Unit	`requestDisallowInterceptTouchEvent(disallowIntercept: Boolean)`
open Unit	`requestLayout()`
open Unit	`scrollBy(x: Int, y: Int)`
open Unit	`scrollTo(x: Int, y: Int)`
open Unit	`scrollToPosition(position: Int)` Convenience method to scroll to a certain position.
open Unit	`sendAccessibilityEventUnchecked(event: AccessibilityEvent!)`
open Unit	`setAccessibilityDelegateCompat(@Nullable accessibilityDelegate: RecyclerViewAccessibilityDelegate?)` Sets the accessibility delegate compatibility implementation used by RecyclerView.
open Unit	`setAdapter(@Nullable adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?)` Set a new adapter to provide child views on demand.
open Unit	`setChildDrawingOrderCallback(@Nullable childDrawingOrderCallback: RecyclerView.ChildDrawingOrderCallback?)` Sets the `ChildDrawingOrderCallback` to be used for drawing children.
open Unit	`setClipToPadding(clipToPadding: Boolean)`
open Unit	`setEdgeEffectFactory(@NonNull edgeEffectFactory: RecyclerView.EdgeEffectFactory)` Set a `EdgeEffectFactory` for this `RecyclerView`.
open Unit	`setHasFixedSize(hasFixedSize: Boolean)` RecyclerView can perform several optimizations if it can know in advance that RecyclerView's size is not affected by the adapter contents.
open Unit	`setItemAnimator(@Nullable animator: RecyclerView.ItemAnimator?)` Sets the `ItemAnimator` that will handle animations involving changes to the items in this RecyclerView.
open Unit	`setItemViewCacheSize(size: Int)` Set the number of offscreen views to retain before adding them to the potentially shared `recycled view pool`.
open Unit	`setLayoutFrozen(frozen: Boolean)` Enable or disable layout and scroll.
open Unit	`setLayoutManager(@Nullable layout: RecyclerView.LayoutManager?)` Set the `LayoutManager` that this RecyclerView will use.
open Unit	`setLayoutTransition(transition: LayoutTransition!)`
open Unit	`setNestedScrollingEnabled(enabled: Boolean)`
open Unit	`setOnFlingListener(@Nullable onFlingListener: RecyclerView.OnFlingListener?)` Set a `OnFlingListener` for this `RecyclerView`.
open Unit	`setOnScrollListener(@Nullable listener: RecyclerView.OnScrollListener?)` Set a listener that will be notified of any changes in scroll state or position.
open Unit	`setPreserveFocusAfterLayout(preserveFocusAfterLayout: Boolean)` Set whether the RecyclerView should try to keep the same Item focused after a layout calculation or not.
open Unit	`setRecycledViewPool(@Nullable pool: RecyclerView.RecycledViewPool?)` Recycled view pools allow multiple RecyclerViews to share a common pool of scrap views.
open Unit	`setRecyclerListener(@Nullable listener: RecyclerView.RecyclerListener?)` Register a listener that will be notified whenever a child view is recycled.
open Unit	`setScrollingTouchSlop(slopConstant: Int)` Configure the scrolling touch slop for a specific use case.
open Unit	`setViewCacheExtension(@Nullable extension: RecyclerView.ViewCacheExtension?)` Sets a new `ViewCacheExtension` to be used by the Recycler.
open Unit	`smoothScrollBy(@Px dx: Int, @Px dy: Int)` Animate a scroll by the given amount of pixels along either axis.
open Unit	`smoothScrollBy(@Px dx: Int, @Px dy: Int, @Nullable interpolator: Interpolator?)` Animate a scroll by the given amount of pixels along either axis.
open Unit	`smoothScrollBy(@Px dx: Int, @Px dy: Int, @Nullable interpolator: Interpolator?, duration: Int)` Smooth scrolls the RecyclerView by a given distance.
open Unit	`smoothScrollToPosition(position: Int)` Starts a smooth scroll to an adapter position.
open Boolean	`startNestedScroll(axes: Int)`
open Boolean	`startNestedScroll(axes: Int, type: Int)`
open Unit	`stopNestedScroll()`
open Unit	`stopNestedScroll(type: Int)`
open Unit	`stopScroll()` Stop any current scroll in progress, such as one started by `smoothScrollBy(int, int)`, `fling(int, int)` or a touch-initiated fling.
Unit	`suppressLayout(suppress: Boolean)` Tells this RecyclerView to suppress all layout and scroll calls until layout suppression is disabled with a later call to suppressLayout(false).
open Unit	`swapAdapter(@Nullable adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?, removeAndRecycleExistingViews: Boolean)` Swaps the current adapter with the provided one.

Protected methods
open Boolean	`checkLayoutParams(p: LayoutParams!)`
open Unit	`dispatchRestoreInstanceState(container: SparseArray<Parcelable!>!)` Override to prevent thawing of any views created by the adapter.
open Unit	`dispatchSaveInstanceState(container: SparseArray<Parcelable!>!)` Override to prevent freezing of any views created by the adapter.
open LayoutParams!	`generateDefaultLayoutParams()`
open LayoutParams!	`generateLayoutParams(p: LayoutParams!)`
open Int	`getChildDrawingOrder(childCount: Int, i: Int)`
open Unit	`onAttachedToWindow()`
open Unit	`onDetachedFromWindow()`
open Unit	`onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int)`
open Unit	`onMeasure(widthSpec: Int, heightSpec: Int)`
open Boolean	`onRequestFocusInDescendants(direction: Int, previouslyFocusedRect: Rect!)`
open Unit	`onRestoreInstanceState(state: Parcelable!)`
open Parcelable?	`onSaveInstanceState()`
open Unit	`onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int)`
open Unit	`removeDetachedView(child: View!, animate: Boolean)`

Constants

HORIZONTAL

static val HORIZONTAL: Int

Value: LinearLayout.HORIZONTAL

INVALID_TYPE

static val INVALID_TYPE: Int

Value: -1

NO_ID

static val NO_ID: Long

Value: -1

NO_POSITION

static val NO_POSITION: Int

Value: -1

SCROLL_STATE_DRAGGING

static val SCROLL_STATE_DRAGGING: Int

The RecyclerView is currently being dragged by outside input such as user touch input.

Value: 1

See Also

#getScrollState()

SCROLL_STATE_IDLE

static val SCROLL_STATE_IDLE: Int

The RecyclerView is not currently scrolling.

Value: 0

See Also

#getScrollState()

SCROLL_STATE_SETTLING

static val SCROLL_STATE_SETTLING: Int

The RecyclerView is currently animating to a final position while not under outside control.

Value: 2

See Also

#getScrollState()

TOUCH_SLOP_DEFAULT

static val TOUCH_SLOP_DEFAULT: Int

Constant for use with setScrollingTouchSlop(int). Indicates that the RecyclerView should use the standard touch slop for smooth, continuous scrolling.

Value: 0

TOUCH_SLOP_PAGING

static val TOUCH_SLOP_PAGING: Int

Constant for use with setScrollingTouchSlop(int). Indicates that the RecyclerView should use the standard touch slop for scrolling widgets that snap to a page or other coarse-grained barrier.

Value: 1

UNDEFINED_DURATION

static val UNDEFINED_DURATION: Int

Constant that represents that a duration has not been defined.

Value: Integer.MIN_VALUE

VERTICAL

static val VERTICAL: Int

Value: LinearLayout.VERTICAL

Public constructors

<init>

RecyclerView(@NonNull context: Context)

<init>

RecyclerView(
    @NonNull context: Context, 
    @Nullable attrs: AttributeSet?)

<init>

RecyclerView(
    @NonNull context: Context, 
    @Nullable attrs: AttributeSet?, 
    defStyleAttr: Int)

Public methods

addFocusables

open fun addFocusables(
    views: ArrayList<View!>!, 
    direction: Int, 
    focusableMode: Int
): Unit

addItemDecoration

open fun addItemDecoration(
    @NonNull decor: RecyclerView.ItemDecoration, 
    index: Int
): Unit

Add an ItemDecoration to this RecyclerView. Item decorations can affect both measurement and drawing of individual item views.

Item decorations are ordered. Decorations placed earlier in the list will be run/queried/drawn first for their effects on item views. Padding added to views will be nested; a padding added by an earlier decoration will mean further item decorations in the list will be asked to draw/pad within the previous decoration's given area.

Parameters
`decor`	RecyclerView.ItemDecoration: Decoration to add
`index`	Int: Position in the decoration chain to insert this decoration at. If this value is negative the decoration will be added at the end.

addItemDecoration

open fun addItemDecoration(@NonNull decor: RecyclerView.ItemDecoration): Unit

Add an ItemDecoration to this RecyclerView. Item decorations can affect both measurement and drawing of individual item views.

Parameters
`decor`	RecyclerView.ItemDecoration: Decoration to add

addOnChildAttachStateChangeListener

open fun addOnChildAttachStateChangeListener(@NonNull listener: RecyclerView.OnChildAttachStateChangeListener): Unit

This listener will be called when a LayoutManager or the RecyclerView decides that a child view is no longer needed. If an application associates expensive or heavyweight data with item views, this may be a good place to release or free those resources.

Parameters
`listener`	RecyclerView.OnChildAttachStateChangeListener: Listener to register

addOnItemTouchListener

open fun addOnItemTouchListener(@NonNull listener: RecyclerView.OnItemTouchListener): Unit

Add an OnItemTouchListener to intercept touch events before they are dispatched to child views or this view's standard scrolling behavior.

Client code may use listeners to implement item manipulation behavior. Once a listener returns true from OnItemTouchListener#onInterceptTouchEvent(RecyclerView, MotionEvent) its OnItemTouchListener#onTouchEvent(RecyclerView, MotionEvent) method will be called for each incoming MotionEvent until the end of the gesture.

Parameters
`listener`	RecyclerView.OnItemTouchListener: Listener to add

See Also

SimpleOnItemTouchListener

addOnScrollListener

open fun addOnScrollListener(@NonNull listener: RecyclerView.OnScrollListener): Unit

Add a listener that will be notified of any changes in scroll state or position.

Components that add a listener should take care to remove it when finished. Other components that take ownership of a view may call clearOnScrollListeners() to remove all attached listeners.

Parameters
`listener`	RecyclerView.OnScrollListener: listener to set

clearOnChildAttachStateChangeListeners

open fun clearOnChildAttachStateChangeListeners(): Unit

Removes all listeners that were added via addOnChildAttachStateChangeListener(OnChildAttachStateChangeListener).

clearOnScrollListeners

open fun clearOnScrollListeners(): Unit

Remove all secondary listener that were notified of any changes in scroll state or position.

computeHorizontalScrollExtent

open fun computeHorizontalScrollExtent(): Int

Compute the horizontal extent of the horizontal scrollbar's thumb within the horizontal range. This value is used to compute the length of the thumb within the scrollbar's track.

The range is expressed in arbitrary units that must be the same as the units used by computeHorizontalScrollRange() and computeHorizontalScrollOffset().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeHorizontalScrollExtent(RecyclerView.State) in your LayoutManager.

Return
`Int`	The horizontal extent of the scrollbar's thumb

See Also

RecyclerView.LayoutManager#computeHorizontalScrollExtent(RecyclerView.State)

computeHorizontalScrollOffset

open fun computeHorizontalScrollOffset(): Int

Compute the horizontal offset of the horizontal scrollbar's thumb within the horizontal range. This value is used to compute the length of the thumb within the scrollbar's track.

The range is expressed in arbitrary units that must be the same as the units used by computeHorizontalScrollRange() and computeHorizontalScrollExtent().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeHorizontalScrollOffset(RecyclerView.State) in your LayoutManager.

Return
`Int`	The horizontal offset of the scrollbar's thumb

See Also

RecyclerView.LayoutManager#computeHorizontalScrollOffset

computeHorizontalScrollRange

open fun computeHorizontalScrollRange(): Int

Compute the horizontal range that the horizontal scrollbar represents.

The range is expressed in arbitrary units that must be the same as the units used by computeHorizontalScrollExtent() and computeHorizontalScrollOffset().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeHorizontalScrollRange(RecyclerView.State) in your LayoutManager.

Return
`Int`	The total horizontal range represented by the vertical scrollbar

See Also

RecyclerView.LayoutManager#computeHorizontalScrollRange(RecyclerView.State)

computeVerticalScrollExtent

open fun computeVerticalScrollExtent(): Int

Compute the vertical extent of the vertical scrollbar's thumb within the vertical range. This value is used to compute the length of the thumb within the scrollbar's track.

The range is expressed in arbitrary units that must be the same as the units used by computeVerticalScrollRange() and computeVerticalScrollOffset().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeVerticalScrollExtent(RecyclerView.State) in your LayoutManager.

Return
`Int`	The vertical extent of the scrollbar's thumb

See Also

RecyclerView.LayoutManager#computeVerticalScrollExtent(RecyclerView.State)

computeVerticalScrollOffset

open fun computeVerticalScrollOffset(): Int

Compute the vertical offset of the vertical scrollbar's thumb within the vertical range. This value is used to compute the length of the thumb within the scrollbar's track.

The range is expressed in arbitrary units that must be the same as the units used by computeVerticalScrollRange() and computeVerticalScrollExtent().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeVerticalScrollOffset(RecyclerView.State) in your LayoutManager.

Return
`Int`	The vertical offset of the scrollbar's thumb

See Also

RecyclerView.LayoutManager#computeVerticalScrollOffset

computeVerticalScrollRange

open fun computeVerticalScrollRange(): Int

Compute the vertical range that the vertical scrollbar represents.

The range is expressed in arbitrary units that must be the same as the units used by computeVerticalScrollExtent() and computeVerticalScrollOffset().

Default implementation returns 0.

If you want to support scroll bars, override RecyclerView.LayoutManager#computeVerticalScrollRange(RecyclerView.State) in your LayoutManager.

Return
`Int`	The total vertical range represented by the vertical scrollbar

See Also

RecyclerView.LayoutManager#computeVerticalScrollRange(RecyclerView.State)

dispatchNestedFling

open fun dispatchNestedFling(
    velocityX: Float, 
    velocityY: Float, 
    consumed: Boolean
): Boolean

dispatchNestedPreFling

open fun dispatchNestedPreFling(
    velocityX: Float, 
    velocityY: Float
): Boolean

dispatchNestedPreScroll

open fun dispatchNestedPreScroll(
    dx: Int, 
    dy: Int, 
    consumed: IntArray?, 
    offsetInWindow: IntArray?
): Boolean

dispatchNestedPreScroll

open fun dispatchNestedPreScroll(
    dx: Int, 
    dy: Int, 
    consumed: IntArray?, 
    offsetInWindow: IntArray?, 
    type: Int
): Boolean

dispatchNestedScroll

open fun dispatchNestedScroll(
    dxConsumed: Int, 
    dyConsumed: Int, 
    dxUnconsumed: Int, 
    dyUnconsumed: Int, 
    offsetInWindow: IntArray?
): Boolean

dispatchNestedScroll

open fun dispatchNestedScroll(
    dxConsumed: Int, 
    dyConsumed: Int, 
    dxUnconsumed: Int, 
    dyUnconsumed: Int, 
    offsetInWindow: IntArray?, 
    type: Int
): Boolean

dispatchNestedScroll

fun dispatchNestedScroll(
    dxConsumed: Int, 
    dyConsumed: Int, 
    dxUnconsumed: Int, 
    dyUnconsumed: Int, 
    offsetInWindow: IntArray?, 
    type: Int, 
    @NonNull consumed: IntArray
): Unit

dispatchPopulateAccessibilityEvent

open fun dispatchPopulateAccessibilityEvent(event: AccessibilityEvent!): Boolean

draw

open fun draw(c: Canvas!): Unit

drawChild

open fun drawChild(
    canvas: Canvas!, 
    child: View!, 
    drawingTime: Long
): Boolean

findChildViewUnder

@Nullable open fun findChildViewUnder(
    x: Float, 
    y: Float
): View?

Find the topmost view under the given point.

Parameters
`x`	Float: Horizontal position in pixels to search
`y`	Float: Vertical position in pixels to search

Return
`View?`	The child view under (x, y) or null if no matching child is found

findContainingItemView

@Nullable open fun findContainingItemView(@NonNull view: View): View?

Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the RecyclerView. This returned view can be used to get the ViewHolder by calling getChildViewHolder(View).

Parameters
`view`	View: The view that is a descendant of the RecyclerView.

Return
`View?`	The direct child of the RecyclerView which contains the given view or null if the provided view is not a descendant of this RecyclerView.

See Also

#getChildViewHolder(View)
#findContainingViewHolder(View)

findContainingViewHolder

@Nullable open fun findContainingViewHolder(@NonNull view: View): RecyclerView.ViewHolder?

Returns the ViewHolder that contains the given view.

Parameters
`view`	View: The view that is a descendant of the RecyclerView.

Return
`RecyclerView.ViewHolder?`	The ViewHolder that contains the given view or null if the provided view is not a descendant of this RecyclerView.

findViewHolderForAdapterPosition

@Nullable open fun findViewHolderForAdapterPosition(position: Int): RecyclerView.ViewHolder?

Return the ViewHolder for the item in the given position of the data set. Unlike findViewHolderForLayoutPosition(int) this method takes into account any pending adapter changes that may not be reflected to the layout yet. On the other hand, if Adapter#notifyDataSetChanged() has been called but the new layout has not been calculated yet, this method will return null since the new positions of views are unknown until the layout is calculated.

This method checks only the children of RecyclerView. If the item at the given position is not laid out, it will not create a new one.

When the ItemAnimator is running a change animation, there might be 2 ViewHolders representing the same Item. In this case, the updated ViewHolder will be returned.

Parameters
`position`	Int: The position of the item in the data set of the adapter

Return
`RecyclerView.ViewHolder?`	The ViewHolder at `position` or null if there is no such item

findViewHolderForItemId

open fun findViewHolderForItemId(id: Long): RecyclerView.ViewHolder!

Return the ViewHolder for the item with the given id. The RecyclerView must use an Adapter with stableIds to return a non-null value.

This method checks only the children of RecyclerView. If the item with the given id is not laid out, it will not create a new one. When the ItemAnimator is running a change animation, there might be 2 ViewHolders with the same id. In this case, the updated ViewHolder will be returned.

Parameters
`id`	Long: The id for the requested item

Return
`RecyclerView.ViewHolder!`	The ViewHolder with the given `id` or null if there is no such item

findViewHolderForLayoutPosition

@Nullable open fun findViewHolderForLayoutPosition(position: Int): RecyclerView.ViewHolder?

Return the ViewHolder for the item in the given position of the data set as of the latest layout pass.

This method checks only the children of RecyclerView. If the item at the given position is not laid out, it will not create a new one.

Note that when Adapter contents change, ViewHolder positions are not updated until the next layout calculation. If there are pending adapter updates, the return value of this method may not match your adapter contents. You can use #ViewHolder#getBindingAdapterPosition() to get the current adapter position of a ViewHolder. If the Adapter that is assigned to the RecyclerView is an adapter that combines other adapters (e.g. ConcatAdapter), you can use the ViewHolder#getBindingAdapter()) to find the position relative to the Adapter that bound the ViewHolder.

When the ItemAnimator is running a change animation, there might be 2 ViewHolders with the same layout position representing the same Item. In this case, the updated ViewHolder will be returned.

Parameters
`position`	Int: The position of the item in the data set of the adapter

Return
`RecyclerView.ViewHolder?`	The ViewHolder at `position` or null if there is no such item

findViewHolderForPosition

@Nullable open fun findViewHolderForPosition(position: Int): RecyclerView.ViewHolder?

Deprecated: use findViewHolderForLayoutPosition(int) or findViewHolderForAdapterPosition(int)

fling

open fun fling(
    velocityX: Int, 
    velocityY: Int
): Boolean

Begin a standard fling with an initial velocity along each axis in pixels per second. If the velocity given is below the system-defined minimum this method will return false and no fling will occur.

Parameters
`velocityX`	Int: Initial horizontal velocity in pixels per second
`velocityY`	Int: Initial vertical velocity in pixels per second

Return
`Boolean`	true if the fling was started, false if the velocity was too low to fling or LayoutManager does not support scrolling in the axis fling is issued.

See Also

focusSearch

open fun focusSearch(
    focused: View!, 
    direction: Int
): View!

Since RecyclerView is a collection ViewGroup that includes virtual children (items that are in the Adapter but not visible in the UI), it employs a more involved focus search strategy that differs from other ViewGroups.

It first does a focus search within the RecyclerView. If this search finds a View that is in the focus direction with respect to the currently focused View, RecyclerView returns that child as the next focus target. When it cannot find such child, it calls LayoutManager#onFocusSearchFailed(View, int, Recycler, State) to layout more Views in the focus search direction. If LayoutManager adds a View that matches the focus search criteria, it will be returned as the focus search result. Otherwise, RecyclerView will call parent to handle the focus search like a regular ViewGroup.

When the direction is View#FOCUS_FORWARD or View#FOCUS_BACKWARD, a View that is not in the focus direction is still valid focus target which may not be the desired behavior if the Adapter has more children in the focus direction. To handle this case, RecyclerView converts the focus direction to an absolute direction and makes a preliminary focus search in that direction. If there are no Views to gain focus, it will call LayoutManager#onFocusSearchFailed(View, int, Recycler, State) before running a focus search with the original (relative) direction. This allows RecyclerView to provide better candidates to the focus search while still allowing the view system to take focus from the RecyclerView and give it to a more suitable child if such child exists.

Parameters
`focused`	View!: The view that currently has focus
`direction`	Int: One of `View#FOCUS_UP`, `View#FOCUS_DOWN`, `View#FOCUS_LEFT`, `View#FOCUS_RIGHT`, `View#FOCUS_FORWARD`, `View#FOCUS_BACKWARD` or 0 for not applicable.

Return
`View!`	A new View that can be the next focus after the focused View

generateLayoutParams

open fun generateLayoutParams(attrs: AttributeSet!): LayoutParams!

getAccessibilityClassName

open fun getAccessibilityClassName(): CharSequence!

getAdapter

@Nullable open fun getAdapter(): RecyclerView.Adapter<RecyclerView.ViewHolder!>?

Retrieves the previously set adapter or null if no adapter is set.

Return
`RecyclerView.Adapter<RecyclerView.ViewHolder!>?`	The previously set adapter

See Also

#setAdapter(Adapter)

getBaseline

open fun getBaseline(): Int

Return the offset of the RecyclerView's text baseline from the its top boundary. If the LayoutManager of this RecyclerView does not support baseline alignment, this method returns -1.

Return
`Int`	the offset of the baseline within the RecyclerView's bounds or -1 if baseline alignment is not supported

getChildAdapterPosition

open fun getChildAdapterPosition(@NonNull child: View): Int

Return the adapter position that the given child view corresponds to.

Parameters
`child`	View: Child View to query

Return
`Int`	Adapter position corresponding to the given view or `NO_POSITION`

getChildItemId

open fun getChildItemId(@NonNull child: View): Long

Return the stable item id that the given child view corresponds to.

Parameters
`child`	View: Child View to query

Return
`Long`	Item id corresponding to the given view or `NO_ID`

getChildLayoutPosition

open fun getChildLayoutPosition(@NonNull child: View): Int

Return the adapter position of the given child view as of the latest completed layout pass.

This position may not be equal to Item's adapter position if there are pending changes in the adapter which have not been reflected to the layout yet.

Parameters
`child`	View: Child View to query

Return
`Int`	Adapter position of the given View as of last layout pass or `NO_POSITION` if the View is representing a removed item.

getChildPosition

open fun getChildPosition(@NonNull child: View): Int

Deprecated: use getChildAdapterPosition(View) or getChildLayoutPosition(View).

getChildViewHolder

open fun getChildViewHolder(@NonNull child: View): RecyclerView.ViewHolder!

Retrieve the ViewHolder for the given child view.

Parameters
`child`	View: Child of this RecyclerView to query for its ViewHolder

Return
`RecyclerView.ViewHolder!`	The child view's ViewHolder

getClipToPadding

open fun getClipToPadding(): Boolean

Returns whether this RecyclerView will clip its children to its padding, and resize (but not clip) any EdgeEffect to the padded region, if padding is present.

By default, children are clipped to the padding of their parent RecyclerView. This clipping behavior is only enabled if padding is non-zero.

Return
`Boolean`	true if this RecyclerView clips children to its padding and resizes (but doesn't clip) any EdgeEffect to the padded region, false otherwise.

getCompatAccessibilityDelegate

@Nullable open fun getCompatAccessibilityDelegate(): RecyclerViewAccessibilityDelegate?

Returns the accessibility delegate compatibility implementation used by the RecyclerView.

Return
`RecyclerViewAccessibilityDelegate?`	An instance of AccessibilityDelegateCompat used by RecyclerView

getDecoratedBoundsWithMargins

open fun getDecoratedBoundsWithMargins(
    @NonNull view: View, 
    @NonNull outBounds: Rect
): Unit

Returns the bounds of the view including its decoration and margins.

Parameters
`view`	View: The view element to check
`outBounds`	Rect: A rect that will receive the bounds of the element including its decoration and margins.

getEdgeEffectFactory

@NonNull open fun getEdgeEffectFactory(): RecyclerView.EdgeEffectFactory

Retrieves the previously set EdgeEffectFactory or the default factory if nothing was set.

Return
`RecyclerView.EdgeEffectFactory`	The previously set `EdgeEffectFactory`

See Also

#setEdgeEffectFactory(EdgeEffectFactory)

getItemAnimator

@Nullable open fun getItemAnimator(): RecyclerView.ItemAnimator?

Gets the current ItemAnimator for this RecyclerView. A null return value indicates that there is no animator and that item changes will happen without any animations. By default, RecyclerView instantiates and uses an instance of DefaultItemAnimator.

Return
`RecyclerView.ItemAnimator?`	ItemAnimator The current ItemAnimator. If null, no animations will occur when changes occur to the items in this RecyclerView.

getItemDecorationAt

@NonNull open fun getItemDecorationAt(index: Int): RecyclerView.ItemDecoration

Returns an ItemDecoration previously added to this RecyclerView.

Parameters
`index`	Int: The index position of the desired ItemDecoration.

Return
`RecyclerView.ItemDecoration`	the ItemDecoration at index position

Exceptions
`IndexOutOfBoundsException`	on invalid index

getItemDecorationCount

open fun getItemDecorationCount(): Int

Returns the number of ItemDecoration currently added to this RecyclerView.

Return
`Int`	number of ItemDecorations currently added added to this RecyclerView.

getLayoutManager

@Nullable open fun getLayoutManager(): RecyclerView.LayoutManager?

Return the LayoutManager currently responsible for layout policy for this RecyclerView.

Return
`RecyclerView.LayoutManager?`	The currently bound LayoutManager

getMaxFlingVelocity

open fun getMaxFlingVelocity(): Int

Returns the maximum fling velocity used by this RecyclerView.

Return
`Int`	The maximum fling velocity used by this RecyclerView.

getMinFlingVelocity

open fun getMinFlingVelocity(): Int

Returns the minimum velocity to start a fling.

Return
`Int`	The minimum velocity to start a fling

getOnFlingListener

@Nullable open fun getOnFlingListener(): RecyclerView.OnFlingListener?

Get the current OnFlingListener from this RecyclerView.

Return
`RecyclerView.OnFlingListener?`	The `OnFlingListener` instance currently set (can be null).

getPreserveFocusAfterLayout

open fun getPreserveFocusAfterLayout(): Boolean

Returns true if the RecyclerView should attempt to preserve currently focused Adapter Item's focus even if the View representing the Item is replaced during a layout calculation.

By default, this value is true.

Return
`Boolean`	True if the RecyclerView will try to preserve focused Item after a layout if it loses focus.

See Also

#setPreserveFocusAfterLayout(boolean)

getRecycledViewPool

@NonNull open fun getRecycledViewPool(): RecyclerView.RecycledViewPool

Retrieve this RecyclerView's RecycledViewPool. This method will never return null; if no pool is set for this view a new one will be created. See setRecycledViewPool for more information.

Return
`RecyclerView.RecycledViewPool`	The pool used to store recycled item views for reuse.

See Also

#setRecycledViewPool(RecycledViewPool)

getScrollState

open fun getScrollState(): Int

Return the current scrolling state of the RecyclerView.

Return
`Int`	`SCROLL_STATE_IDLE`, `SCROLL_STATE_DRAGGING` or `SCROLL_STATE_SETTLING`

hasFixedSize

open fun hasFixedSize(): Boolean

Return
`Boolean`	true if the app has specified that changes in adapter content cannot change the size of the RecyclerView itself.

hasNestedScrollingParent

open fun hasNestedScrollingParent(): Boolean

hasNestedScrollingParent

open fun hasNestedScrollingParent(type: Int): Boolean

hasPendingAdapterUpdates

open fun hasPendingAdapterUpdates(): Boolean

Returns whether there are pending adapter updates which are not yet applied to the layout.

If this method returns true, it means that what user is currently seeing may not reflect them adapter contents (depending on what has changed). You may use this information to defer or cancel some operations.

This method returns true if RecyclerView has not yet calculated the first layout after it is attached to the Window or the Adapter has been replaced.

Return
`Boolean`	True if there are some adapter updates which are not yet reflected to layout or false if layout is up to date.

invalidateItemDecorations

open fun invalidateItemDecorations(): Unit

Invalidates all ItemDecorations. If RecyclerView has item decorations, calling this method will trigger a requestLayout() call.

isAnimating

open fun isAnimating(): Boolean

Returns true if RecyclerView is currently running some animations.

If you want to be notified when animations are finished, use ItemAnimator#isRunning(ItemAnimator.ItemAnimatorFinishedListener).

Return
`Boolean`	True if there are some item animations currently running or waiting to be started.

isAttachedToWindow

open fun isAttachedToWindow(): Boolean

Returns true if RecyclerView is attached to window.

isComputingLayout

open fun isComputingLayout(): Boolean

Returns whether RecyclerView is currently computing a layout.

If this method returns true, it means that RecyclerView is in a lockdown state and any attempt to update adapter contents will result in an exception because adapter contents cannot be changed while RecyclerView is trying to compute the layout.

It is very unlikely that your code will be running during this state as it is called by the framework when a layout traversal happens or RecyclerView starts to scroll in response to system events (touch, accessibility etc).

This case may happen if you have some custom logic to change adapter contents in response to a View callback (e.g. focus change callback) which might be triggered during a layout calculation. In these cases, you should just postpone the change using a Handler or a similar mechanism.

Return
`Boolean`	`true` if RecyclerView is currently computing a layout, `false` otherwise

isLayoutFrozen

open fun isLayoutFrozen(): Boolean

Deprecated: Use isLayoutSuppressed().

Return
`Boolean`	true if layout and scroll are frozen

isLayoutSuppressed

fun isLayoutSuppressed(): Boolean

Returns whether layout and scroll calls on this container are currently being suppressed, due to an earlier call to suppressLayout(boolean).

Return
`Boolean`	true if layout and scroll are currently suppressed, false otherwise.

isNestedScrollingEnabled

open fun isNestedScrollingEnabled(): Boolean

nestedScrollBy

open fun nestedScrollBy(
    x: Int, 
    y: Int
): Unit

Same as RecyclerView#scrollBy(int, int), but also participates in nested scrolling.

Parameters
`x`	Int: The amount of horizontal scroll requested
`y`	Int: The amount of vertical scroll requested

See Also

androidx.core.view.NestedScrollingChild

offsetChildrenHorizontal

open fun offsetChildrenHorizontal(@Px dx: Int): Unit

Offset the bounds of all child views by dx pixels. Useful for implementing simple scrolling in LayoutManagers.

Parameters
`dx`	Int: Horizontal pixel offset to apply to the bounds of all child views

offsetChildrenVertical

open fun offsetChildrenVertical(@Px dy: Int): Unit

Offset the bounds of all child views by dy pixels. Useful for implementing simple scrolling in LayoutManagers.

Parameters
`dy`	Int: Vertical pixel offset to apply to the bounds of all child views

onChildAttachedToWindow

open fun onChildAttachedToWindow(@NonNull child: View): Unit

Called when an item view is attached to this RecyclerView.

Subclasses of RecyclerView may want to perform extra bookkeeping or modifications of child views as they become attached. This will be called before a LayoutManager measures or lays out the view and is a good time to perform these changes.

Parameters
`child`	View: Child view that is now attached to this RecyclerView and its associated window

onChildDetachedFromWindow

open fun onChildDetachedFromWindow(@NonNull child: View): Unit

Called when an item view is detached from this RecyclerView.

Subclasses of RecyclerView may want to perform extra bookkeeping or modifications of child views as they become detached. This will be called as a LayoutManager fully detaches the child view from the parent and its window.

Parameters
`child`	View: Child view that is now detached from this RecyclerView and its associated window

onDraw

open fun onDraw(c: Canvas!): Unit

onGenericMotionEvent

open fun onGenericMotionEvent(event: MotionEvent!): Boolean

onInterceptTouchEvent

open fun onInterceptTouchEvent(e: MotionEvent!): Boolean

onScrollStateChanged

open fun onScrollStateChanged(state: Int): Unit

Called when the scroll state of this RecyclerView changes. Subclasses should use this method to respond to state changes instead of an explicit listener.

This method will always be invoked before listeners, but after the LayoutManager responds to the scroll state change.

Parameters
`state`	Int: the new scroll state, one of `SCROLL_STATE_IDLE`, `SCROLL_STATE_DRAGGING` or `SCROLL_STATE_SETTLING`

onScrolled

open fun onScrolled(
    @Px dx: Int, 
    @Px dy: Int
): Unit

Called when the scroll position of this RecyclerView changes. Subclasses should use this method to respond to scrolling within the adapter's data set instead of an explicit listener.

This method will always be invoked before listeners. If a subclass needs to perform any additional upkeep or bookkeeping after scrolling but before listeners run, this is a good place to do so.

This differs from View#onScrollChanged(int, int, int, int) in that it receives the distance scrolled in either direction within the adapter's data set instead of absolute scroll coordinates. Since RecyclerView cannot compute the absolute scroll position from any arbitrary point in the data set, onScrollChanged will always receive the current View#getScrollX() and View#getScrollY() values which do not correspond to the data set scroll position. However, some subclasses may choose to use these fields as special offsets.

Parameters
`dx`	Int: horizontal distance scrolled in pixels
`dy`	Int: vertical distance scrolled in pixels

onTouchEvent

open fun onTouchEvent(e: MotionEvent!): Boolean

removeItemDecoration

open fun removeItemDecoration(@NonNull decor: RecyclerView.ItemDecoration): Unit

Remove an ItemDecoration from this RecyclerView.

The given decoration will no longer impact the measurement and drawing of item views.

Parameters
`decor`	RecyclerView.ItemDecoration: Decoration to remove

See Also

#addItemDecoration(ItemDecoration)

removeItemDecorationAt

open fun removeItemDecorationAt(index: Int): Unit

Removes the ItemDecoration associated with the supplied index position.

Parameters
`index`	Int: The index position of the ItemDecoration to be removed.

removeOnChildAttachStateChangeListener

open fun removeOnChildAttachStateChangeListener(@NonNull listener: RecyclerView.OnChildAttachStateChangeListener): Unit

Removes the provided listener from child attached state listeners list.

Parameters
`listener`	RecyclerView.OnChildAttachStateChangeListener: Listener to unregister

removeOnItemTouchListener

open fun removeOnItemTouchListener(@NonNull listener: RecyclerView.OnItemTouchListener): Unit

Remove an OnItemTouchListener. It will no longer be able to intercept touch events.

Parameters
`listener`	RecyclerView.OnItemTouchListener: Listener to remove

removeOnScrollListener

open fun removeOnScrollListener(@NonNull listener: RecyclerView.OnScrollListener): Unit

Remove a listener that was notified of any changes in scroll state or position.

Parameters
`listener`	RecyclerView.OnScrollListener: listener to set or null to clear

requestChildFocus

open fun requestChildFocus(
    child: View!, 
    focused: View!
): Unit

requestChildRectangleOnScreen

open fun requestChildRectangleOnScreen(
    child: View!, 
    rect: Rect!, 
    immediate: Boolean
): Boolean

requestDisallowInterceptTouchEvent

open fun requestDisallowInterceptTouchEvent(disallowIntercept: Boolean): Unit

requestLayout

open fun requestLayout(): Unit

scrollBy

open fun scrollBy(
    x: Int, 
    y: Int
): Unit

scrollTo

open fun scrollTo(
    x: Int, 
    y: Int
): Unit

scrollToPosition

open fun scrollToPosition(position: Int): Unit

Convenience method to scroll to a certain position. RecyclerView does not implement scrolling logic, rather forwards the call to RecyclerView.LayoutManager#scrollToPosition(int)

Parameters
`position`	Int: Scroll to this adapter position

See Also

RecyclerView.LayoutManager#scrollToPosition(int)

sendAccessibilityEventUnchecked

open fun sendAccessibilityEventUnchecked(event: AccessibilityEvent!): Unit

setAccessibilityDelegateCompat

open fun setAccessibilityDelegateCompat(@Nullable accessibilityDelegate: RecyclerViewAccessibilityDelegate?): Unit

Sets the accessibility delegate compatibility implementation used by RecyclerView.

Parameters
`accessibilityDelegate`	RecyclerViewAccessibilityDelegate?: The accessibility delegate to be used by RecyclerView.

setAdapter

open fun setAdapter(@Nullable adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?): Unit

Set a new adapter to provide child views on demand.

When adapter is changed, all existing views are recycled back to the pool. If the pool has only one adapter, it will be cleared.

Parameters
`adapter`	RecyclerView.Adapter<RecyclerView.ViewHolder!>?: The new adapter to set, or null to set no adapter.

See Also

#swapAdapter(Adapter, boolean)

setChildDrawingOrderCallback

open fun setChildDrawingOrderCallback(@Nullable childDrawingOrderCallback: RecyclerView.ChildDrawingOrderCallback?): Unit

Sets the ChildDrawingOrderCallback to be used for drawing children.

See ViewGroup#getChildDrawingOrder(int, int) for details. Calling this method will always call ViewGroup#setChildrenDrawingOrderEnabled(boolean). The parameter will be true if childDrawingOrderCallback is not null, false otherwise.

Note that child drawing order may be overridden by View's elevation.

Parameters
`childDrawingOrderCallback`	RecyclerView.ChildDrawingOrderCallback?: The ChildDrawingOrderCallback to be used by the drawing system.

setClipToPadding

open fun setClipToPadding(clipToPadding: Boolean): Unit

setEdgeEffectFactory

open fun setEdgeEffectFactory(@NonNull edgeEffectFactory: RecyclerView.EdgeEffectFactory): Unit

Set a EdgeEffectFactory for this RecyclerView.

When a new EdgeEffectFactory is set, any existing over-scroll effects are cleared and new effects are created as needed using EdgeEffectFactory#createEdgeEffect(RecyclerView, int)

Parameters
`edgeEffectFactory`	RecyclerView.EdgeEffectFactory: The `EdgeEffectFactory` instance.

setHasFixedSize

open fun setHasFixedSize(hasFixedSize: Boolean): Unit

RecyclerView can perform several optimizations if it can know in advance that RecyclerView's size is not affected by the adapter contents. RecyclerView can still change its size based on other factors (e.g. its parent's size) but this size calculation cannot depend on the size of its children or contents of its adapter (except the number of items in the adapter).

If your use of RecyclerView falls into this category, set this to true. It will allow RecyclerView to avoid invalidating the whole layout when its adapter contents change.

Parameters
`hasFixedSize`	Boolean: true if adapter changes cannot affect the size of the RecyclerView.

setItemAnimator

open fun setItemAnimator(@Nullable animator: RecyclerView.ItemAnimator?): Unit

Sets the ItemAnimator that will handle animations involving changes to the items in this RecyclerView. By default, RecyclerView instantiates and uses an instance of DefaultItemAnimator. Whether item animations are enabled for the RecyclerView depends on the ItemAnimator and whether the LayoutManager supports item animations.

Parameters
`animator`	RecyclerView.ItemAnimator?: The ItemAnimator being set. If null, no animations will occur when changes occur to the items in this RecyclerView.

setItemViewCacheSize

open fun setItemViewCacheSize(size: Int): Unit

Set the number of offscreen views to retain before adding them to the potentially shared recycled view pool.

The offscreen view cache stays aware of changes in the attached adapter, allowing a LayoutManager to reuse those views unmodified without needing to return to the adapter to rebind them.

Parameters
`size`	Int: Number of views to cache offscreen before returning them to the general recycled view pool

setLayoutFrozen

open fun setLayoutFrozen(frozen: Boolean): Unit

Deprecated: Use suppressLayout(boolean).

Enable or disable layout and scroll. After setLayoutFrozen(true) is called, Layout requests will be postponed until setLayoutFrozen(false) is called; child views are not updated when RecyclerView is frozen, smoothScrollBy(int, int), scrollBy(int, int), scrollToPosition(int) and smoothScrollToPosition(int) are dropped; TouchEvents and GenericMotionEvents are dropped; LayoutManager#onFocusSearchFailed(View, int, Recycler, State) will not be called.

setLayoutFrozen(true) does not prevent app from directly calling , LayoutManager#smoothScrollToPosition( *RecyclerView, State, int).

setAdapter(Adapter) and swapAdapter(Adapter, boolean) will automatically stop frozen.

Note: Running ItemAnimator is not stopped automatically, it's caller's responsibility to call ItemAnimator.end().

Parameters
`frozen`	Boolean: true to freeze layout and scroll, false to re-enable.

setLayoutManager

open fun setLayoutManager(@Nullable layout: RecyclerView.LayoutManager?): Unit

Set the LayoutManager that this RecyclerVie