RecyclerView
open class RecyclerView : ViewGroup, ScrollingView, NestedScrollingChild2, NestedScrollingChild3
kotlin.Any | |||
↳ | android.view.View | ||
↳ | android.view.ViewGroup | ||
↳ | androidx.recyclerview.widget.RecyclerView |
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#getAdapterPosition()
, 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#getAdapterPosition()
. 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 callingadapter.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 useSortedList
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 theandroidx.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 |
Base class for an Adapter |
abstract |
Observer base class for watching changes to an |
abstract |
A callback interface that can be used to alter the drawing order of RecyclerView children. |
open |
EdgeEffectFactory lets you customize the over-scroll edge effect for RecyclerViews. |
abstract |
This class defines the animations that take place on items as changes are made to the adapter. |
abstract |
An ItemDecoration allows the application to add a special drawing and layout offset to specific item views from the adapter's data set. |
abstract |
A |
open |
|
abstract |
A Listener interface that can be attached to a RecylcerView to get notified whenever a ViewHolder is attached to or detached from RecyclerView. |
abstract |
This class defines the behavior of fling if the developer wishes to handle it. |
abstract |
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 |
An OnScrollListener can be added to a RecyclerView to receive messages when a scrolling event has occurred on that RecyclerView. |
open |
RecycledViewPool lets you share Views between multiple RecyclerViews. |
A Recycler is responsible for managing scrapped or detached item views for reuse. |
|
abstract |
A RecyclerListener can be set on a RecyclerView to receive messages whenever a view is recycled. |
open |
An implementation of |
abstract |
Base class for smooth scrolling. |
open |
Contains useful information about the current RecyclerView state like target scroll position or view focus. |
abstract |
ViewCacheExtension is a helper class to provide an additional layer of view caching that can be controlled by the developer. |
abstract |
A ViewHolder describes an item view and metadata about its place within the RecyclerView. |
Constants |
|
---|---|
static Int | |
static Int | |
static Long | |
static Int | |
static Int |
The RecyclerView is currently being dragged by outside input such as user touch input. |
static Int |
The RecyclerView is not currently scrolling. |
static Int |
The RecyclerView is currently animating to a final position while not under outside control. |
static Int |
Constant for use with |
static Int |
Constant for use with |
static Int |
Constant that represents that a duration has not been defined. |
static Int |
Public constructors |
|
---|---|
<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 |
open Unit |
addItemDecoration(@NonNull decor: RecyclerView.ItemDecoration) Add an |
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 |
open Unit |
addOnScrollListener(@NonNull listener: RecyclerView.OnScrollListener) Add a listener that will be notified of any changes in scroll state or position. |
open Unit |
Removes all listeners that were added via |
open Unit |
Remove all secondary listener that were notified of any changes in scroll state or position. |
open Int |
Compute the horizontal extent of the horizontal scrollbar's thumb within the horizontal range. |
open Int |
Compute the horizontal offset of the horizontal scrollbar's thumb within the horizontal range. |
open Int |
Compute the horizontal range that the horizontal scrollbar represents. |
open Int |
Compute the vertical extent of the vertical scrollbar's thumb within the vertical range. |
open Int |
Compute the vertical offset of the vertical scrollbar's thumb within the vertical range. |
open Int |
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 | |
open Boolean | |
open Boolean | |
Unit | |
open Boolean | |
open Unit | |
open Boolean | |
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! |
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 |
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! | |
open RecyclerView.Adapter<RecyclerView.ViewHolder!>? |
Retrieves the previously set adapter or null if no adapter is set. |
open Int |
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 |
open 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. |
open RecyclerViewAccessibilityDelegate? |
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 |
Retrieves the previously set |
open RecyclerView.ItemAnimator? |
Gets the current ItemAnimator for this RecyclerView. |
open RecyclerView.ItemDecoration |
getItemDecorationAt(index: Int) Returns an |
open Int |
Returns the number of |
open RecyclerView.LayoutManager? |
Return the |
open Int |
Returns the maximum fling velocity used by this RecyclerView. |
open Int |
Returns the minimum velocity to start a fling. |
open RecyclerView.OnFlingListener? |
Get the current |
open 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. |
open RecyclerView.RecycledViewPool |
Retrieve this RecyclerView's |
open Int |
Return the current scrolling state of the RecyclerView. |
open Boolean | |
open Boolean | |
open Boolean |
hasNestedScrollingParent(type: Int) |
open Boolean |
Returns whether there are pending adapter updates which are not yet applied to the layout. |
open Unit |
Invalidates all ItemDecorations. |
open Boolean |
Returns true if RecyclerView is currently running some animations. |
open Boolean |
Returns true if RecyclerView is attached to window. |
open Boolean |
Returns whether RecyclerView is currently computing a layout. |
open Boolean | |
Boolean |
Returns whether layout and scroll calls on this container are currently being suppressed, due to an earlier call to |
open Boolean | |
open Unit |
offsetChildrenHorizontal(@Px dx: Int) Offset the bounds of all child views by |
open Unit |
offsetChildrenVertical(@Px dy: Int) Offset the bounds of all child views by |
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 | |
open Boolean |
onGenericMotionEvent(event: MotionEvent!) |
open Boolean | |
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 |
open Unit |
removeItemDecorationAt(index: Int) Removes the |
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 |
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 | |
open Unit | |
open Unit | |
open Unit |
scrollToPosition(position: Int) Convenience method to scroll to a certain position. |
open Unit | |
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 |
open Unit |
setClipToPadding(clipToPadding: Boolean) |
open Unit |
setEdgeEffectFactory(@NonNull edgeEffectFactory: RecyclerView.EdgeEffectFactory) Set a |
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 |
open Unit |
setItemViewCacheSize(size: Int) Set the number of offscreen views to retain before adding them to the potentially shared |
open Unit |
setLayoutFrozen(frozen: Boolean) Enable or disable layout and scroll. |
open Unit |
setLayoutManager(@Nullable layout: RecyclerView.LayoutManager?) Set the |
open Unit |
setLayoutTransition(transition: LayoutTransition!) |
open Unit |
setNestedScrollingEnabled(enabled: Boolean) |
open Unit |
setOnFlingListener(@Nullable onFlingListener: RecyclerView.OnFlingListener?) Set a |
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 |
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 | |
open Unit |
stopNestedScroll(type: Int) |
open Unit |
Stop any current scroll in progress, such as one started by |
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 |
|
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open Boolean | |
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! | |
open LayoutParams! | |
open Int |
getChildDrawingOrder(childCount: Int, i: Int) |
open Unit | |
open Unit | |
open Unit | |
open Unit | |
open Boolean |
onRequestFocusInDescendants(direction: Int, previouslyFocusedRect: Rect!) |
open Unit |
onRestoreInstanceState(state: Parcelable!) |
open Parcelable! | |
open Unit |
onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) |
open Unit |
removeDetachedView(child: View!, animate: Boolean) |
Constants
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
SCROLL_STATE_IDLE
static val SCROLL_STATE_IDLE: Int
The RecyclerView is not currently scrolling.
Value: 0
See Also
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
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
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 |
RecyclerView.ItemDecoration: 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.
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 |
addOnChildAttachStateChangeListener
open fun addOnChildAttachStateChangeListener(@NonNull listener: RecyclerView.OnChildAttachStateChangeListener): Unit
Register a listener that will be notified whenever a child view is attached to or detached from RecyclerView.
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
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 |
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 |
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 |
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 |
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 |
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 |
dispatchNestedFling
open fun dispatchNestedFling(velocityX: Float, velocityY: Float, consumed: Boolean): 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
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. |
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#getAdapterPosition()
to get the current adapter position of a 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 funfindViewHolderForPosition(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. |
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 |
View!: 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
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 fungetChildPosition(@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 |
View: 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 |
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. |
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. |
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
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 funisLayoutFrozen(): 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
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 |
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
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 |
requestChildRectangleOnScreen
open fun requestChildRectangleOnScreen(child: View!, rect: Rect!, immediate: Boolean): Boolean
requestDisallowInterceptTouchEvent
open fun requestDisallowInterceptTouchEvent(disallowIntercept: Boolean): Unit
requestLayout
open fun requestLayout(): 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 |
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
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. |
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 funsetLayoutFrozen(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 RecyclerView will use.
In contrast to other adapter-backed views such as android.widget.ListView
or android.widget.GridView
, RecyclerView allows client code to provide custom layout arrangements for child views. These arrangements are controlled by the LayoutManager
. A LayoutManager must be provided for RecyclerView to function.
Several default strategies are provided for common uses such as lists and grids.
Parameters | |
---|---|
layout |
RecyclerView.LayoutManager?: LayoutManager to use |
setLayoutTransition
open funsetLayoutTransition(transition: LayoutTransition!): Unit
Deprecated: Use setItemAnimator(ItemAnimator)
()}.
setOnFlingListener
open fun setOnFlingListener(@Nullable onFlingListener: RecyclerView.OnFlingListener?): Unit
Set a OnFlingListener
for this RecyclerView
.
If the OnFlingListener
is set then it will receive calls to fling(int,int)
and will be able to intercept them.
Parameters | |
---|---|
onFlingListener |
RecyclerView.OnFlingListener?: The OnFlingListener instance. |
setOnScrollListener
open funsetOnScrollListener(@Nullable listener: RecyclerView.OnScrollListener?): Unit
Deprecated: Use addOnScrollListener(OnScrollListener)
and removeOnScrollListener(OnScrollListener)
Set a listener that will be notified of any changes in scroll state or position.
Parameters | |
---|---|
listener |
RecyclerView.OnScrollListener?: Listener to set or null to clear |
setPreserveFocusAfterLayout
open fun setPreserveFocusAfterLayout(preserveFocusAfterLayout: Boolean): Unit
Set whether the RecyclerView should try to keep the same Item focused after a layout calculation or not.
Usually, LayoutManagers keep focused views visible before and after layout but sometimes, views may lose focus during a layout calculation as their state changes or they are replaced with another view due to type change or animation. In these cases, RecyclerView can request focus on the new view automatically.
Parameters | |
---|---|
preserveFocusAfterLayout |
Boolean: Whether RecyclerView should preserve focused Item during a layout calculations. Defaults to true. |
See Also
setRecycledViewPool
open fun setRecycledViewPool(@Nullable pool: RecyclerView.RecycledViewPool?): Unit
Recycled view pools allow multiple RecyclerViews to share a common pool of scrap views. This can be useful if you have multiple RecyclerViews with adapters that use the same view types, for example if you have several data sets with the same kinds of item views displayed by a androidx.viewpager.widget.ViewPager
.
Parameters | |
---|---|
pool |
RecyclerView.RecycledViewPool?: Pool to set. If this parameter is null a new pool will be created and used. |
setRecyclerListener
open fun setRecyclerListener(@Nullable listener: RecyclerView.RecyclerListener?): Unit
Register a listener that will be notified whenever a child view is recycled.
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.RecyclerListener?: Listener to register, or null to clear |
setScrollingTouchSlop
open fun setScrollingTouchSlop(slopConstant: Int): Unit
Configure the scrolling touch slop for a specific use case. Set up the RecyclerView's scrolling motion threshold based on common usages. Valid arguments are TOUCH_SLOP_DEFAULT
and TOUCH_SLOP_PAGING
.
Parameters | |
---|---|
slopConstant |
Int: One of the TOUCH_SLOP_ constants representing the intended usage of this RecyclerView |
setViewCacheExtension
open fun setViewCacheExtension(@Nullable extension: RecyclerView.ViewCacheExtension?): Unit
Sets a new ViewCacheExtension
to be used by the Recycler.
Parameters | |
---|---|
extension |
RecyclerView.ViewCacheExtension?: ViewCacheExtension to be used or null if you want to clear the existing one. |
smoothScrollBy
open fun smoothScrollBy(@Px dx: Int, @Px dy: Int): Unit
Animate a scroll by the given amount of pixels along either axis.
Parameters | |
---|---|
dx |
Int: Pixels to scroll horizontally |
dy |
Int: Pixels to scroll vertically |
smoothScrollBy
open fun smoothScrollBy(@Px dx: Int, @Px dy: Int, @Nullable interpolator: Interpolator?): Unit
Animate a scroll by the given amount of pixels along either axis.
Parameters | |
---|---|
dx |
Int: Pixels to scroll horizontally |
dy |
Int: Pixels to scroll vertically |
interpolator |
Int: Interpolator to be used for scrolling. If it is null , RecyclerView will use an internal default interpolator. |
smoothScrollBy
open fun smoothScrollBy(@Px dx: Int, @Px dy: Int, @Nullable interpolator: Interpolator?, duration: Int): Unit
Smooth scrolls the RecyclerView by a given distance.
Parameters | |
---|---|
dx |
Int: x distance in pixels. |
dy |
Int: y distance in pixels. |
interpolator |
Int: Interpolator to be used for scrolling. If it is null , RecyclerView will use an internal default interpolator. |
duration |
Int: Duration of the animation in milliseconds. Set to UNDEFINED_DURATION to have the duration be automatically calculated based on an internally defined standard initial velocity. A duration less than 1 (that does not equal UNDEFINED_DURATION), will result in a call to scrollBy(int, int) . |
smoothScrollToPosition
open fun smoothScrollToPosition(position: Int): Unit
Starts a smooth scroll to an adapter position.
To support smooth scrolling, you must override LayoutManager#smoothScrollToPosition(RecyclerView, State, int)
and create a SmoothScroller
.
LayoutManager
is responsible for creating the actual scroll action. If you want to provide a custom smooth scroll logic, override LayoutManager#smoothScrollToPosition(RecyclerView, State, int)
in your LayoutManager.
Parameters | |
---|---|
position |
Int: The adapter position to scroll to |
stopNestedScroll
open fun stopNestedScroll(): Unit
stopScroll
open fun stopScroll(): Unit
Stop any current scroll in progress, such as one started by smoothScrollBy(int, int)
, fling(int, int)
or a touch-initiated fling.
suppressLayout
fun suppressLayout(suppress: Boolean): Unit
Tells this RecyclerView to suppress all layout and scroll calls until layout suppression is disabled with a later call to suppressLayout(false). When layout suppression is disabled, a requestLayout() call is sent if requestLayout() was attempted while layout was being suppressed.
In addition to the layout suppression 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.
suppressLayout(true)
does not prevent app from directly calling
, LayoutManager#smoothScrollToPosition( * RecyclerView, State, int)
.
setAdapter(Adapter)
and swapAdapter(Adapter, boolean)
will automatically stop suppressing.
Note: Running ItemAnimator is not stopped automatically, it's caller's responsibility to call ItemAnimator.end().
Parameters | |
---|---|
suppress |
Boolean: true to suppress layout and scroll, false to re-enable. |
swapAdapter
open fun swapAdapter(@Nullable adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?, removeAndRecycleExistingViews: Boolean): Unit
Swaps the current adapter with the provided one. It is similar to setAdapter(Adapter)
but assumes existing adapter and the new adapter uses the same ViewHolder
and does not clear the RecycledViewPool.
Note that it still calls onAdapterChanged callbacks.
Parameters | |
---|---|
adapter |
RecyclerView.Adapter<RecyclerView.ViewHolder!>?: The new adapter to set, or null to set no adapter. |
removeAndRecycleExistingViews |
RecyclerView.Adapter<RecyclerView.ViewHolder!>?: If set to true, RecyclerView will recycle all existing Views. If adapters have stable ids and/or you want to animate the disappearing views, you may prefer to set this to false. |
See Also
Protected methods
checkLayoutParams
protected open fun checkLayoutParams(p: LayoutParams!): Boolean
dispatchRestoreInstanceState
protected open fun dispatchRestoreInstanceState(container: SparseArray<Parcelable!>!): Unit
Override to prevent thawing of any views created by the adapter.
dispatchSaveInstanceState
protected open fun dispatchSaveInstanceState(container: SparseArray<Parcelable!>!): Unit
Override to prevent freezing of any views created by the adapter.
generateDefaultLayoutParams
protected open fun generateDefaultLayoutParams(): LayoutParams!
generateLayoutParams
protected open fun generateLayoutParams(p: LayoutParams!): LayoutParams!
onAttachedToWindow
protected open fun onAttachedToWindow(): Unit
onDetachedFromWindow
protected open fun onDetachedFromWindow(): Unit
onRequestFocusInDescendants
protected open fun onRequestFocusInDescendants(direction: Int, previouslyFocusedRect: Rect!): Boolean
onRestoreInstanceState
protected open fun onRestoreInstanceState(state: Parcelable!): Unit
onSaveInstanceState
protected open fun onSaveInstanceState(): Parcelable!
removeDetachedView
protected open fun removeDetachedView(child: View!