Android APIs
public class

RecyclerView

extends ViewGroup
implements ScrollingView NestedScrollingChild
java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ android.support.v7.widget.RecyclerView
Known Direct Subclasses

Class Overview

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

Glossary of terms:

  • Adapter: A subclass of RecyclerView.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 getChildAt(int). 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 RecyclerView.Adapter and RecyclerView.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. 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. 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 getAdapterPosition(). Beware that these methods may not be able to calculate adapter positions if 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 RecyclerView.LayoutManager you almost always want to use layout positions whereas when writing an RecyclerView.Adapter, you probably want to use adapter positions.

Summary

Nested Classes
class RecyclerView.Adapter<VH extends RecyclerView.ViewHolder> Base class for an Adapter

Adapters provide a binding from an app-specific data set to views that are displayed within a RecyclerView

class RecyclerView.AdapterDataObserver Observer base class for watching changes to an RecyclerView.Adapter
interface RecyclerView.ChildDrawingOrderCallback A callback interface that can be used to alter the drawing order of RecyclerView children. 
class RecyclerView.ItemAnimator This class defines the animations that take place on items as changes are made to the adapter. 
class RecyclerView.ItemDecoration An ItemDecoration allows the application to add a special drawing and layout offset to specific item views from the adapter's data set. 
class RecyclerView.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. 
class RecyclerView.LayoutParams LayoutParams subclass for children of RecyclerView
interface RecyclerView.OnChildAttachStateChangeListener A Listener interface that can be attached to a RecylcerView to get notified whenever a ViewHolder is attached to or detached from RecyclerView. 
interface RecyclerView.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. 
class RecyclerView.OnScrollListener An OnScrollListener can be set on a RecyclerView to receive messages when a scrolling event has occurred on that RecyclerView. 
class RecyclerView.RecycledViewPool RecycledViewPool lets you share Views between multiple RecyclerViews. 
class RecyclerView.Recycler A Recycler is responsible for managing scrapped or detached item views for reuse. 
interface RecyclerView.RecyclerListener A RecyclerListener can be set on a RecyclerView to receive messages whenever a view is recycled. 
class RecyclerView.SimpleOnItemTouchListener An implementation of RecyclerView.OnItemTouchListener that has empty method bodies and default return values. 
class RecyclerView.SmoothScroller

Base class for smooth scrolling. 

class RecyclerView.State

Contains useful information about the current RecyclerView state like target scroll position or view focus. 

class RecyclerView.ViewCacheExtension ViewCacheExtension is a helper class to provide an additional layer of view caching that can ben controlled by the developer. 
class RecyclerView.ViewHolder A ViewHolder describes an item view and metadata about its place within the RecyclerView. 
XML Attributes
Attribute Name Related Method Description
android.support.v7.recyclerview:layoutManager Class name of the Layout Manager to be used. 
[Expand]
Inherited XML Attributes
From class android.view.ViewGroup
From class android.view.View
Constants
int HORIZONTAL
int INVALID_TYPE
long NO_ID
int NO_POSITION
int SCROLL_STATE_DRAGGING The RecyclerView is currently being dragged by outside input such as user touch input.
int SCROLL_STATE_IDLE The RecyclerView is not currently scrolling.
int SCROLL_STATE_SETTLING The RecyclerView is currently animating to a final position while not under outside control.
int TOUCH_SLOP_DEFAULT Constant for use with setScrollingTouchSlop(int).
int TOUCH_SLOP_PAGING Constant for use with setScrollingTouchSlop(int).
int VERTICAL
[Expand]
Inherited Constants
From class android.view.ViewGroup
From class android.view.View
[Expand]
Inherited Fields
From class android.view.View
Public Constructors
RecyclerView(Context context)
RecyclerView(Context context, AttributeSet attrs)
RecyclerView(Context context, AttributeSet attrs, int defStyle)
Public Methods
void addFocusables(ArrayList<View> views, int direction, int focusableMode)
Adds any focusable views that are descendants of this view (possibly including this view if it is focusable itself) to views.
void addItemDecoration(RecyclerView.ItemDecoration decor)
Add an RecyclerView.ItemDecoration to this RecyclerView.
void addItemDecoration(RecyclerView.ItemDecoration decor, int index)
Add an RecyclerView.ItemDecoration to this RecyclerView.
void addOnChildAttachStateChangeListener(RecyclerView.OnChildAttachStateChangeListener listener)
Register a listener that will be notified whenever a child view is attached to or detached from RecyclerView.
void addOnItemTouchListener(RecyclerView.OnItemTouchListener listener)
Add an RecyclerView.OnItemTouchListener to intercept touch events before they are dispatched to child views or this view's standard scrolling behavior.
void addOnScrollListener(RecyclerView.OnScrollListener listener)
Add a listener that will be notified of any changes in scroll state or position.
void clearOnChildAttachStateChangeListeners()
void clearOnScrollListeners()
Remove all secondary listener that were notified of any changes in scroll state or position.
int computeHorizontalScrollExtent()

Compute the horizontal extent of the horizontal scrollbar's thumb within the horizontal range.

int computeHorizontalScrollOffset()

Compute the horizontal offset of the horizontal scrollbar's thumb within the horizontal range.

int computeHorizontalScrollRange()

Compute the horizontal range that the horizontal scrollbar represents.

int computeVerticalScrollExtent()

Compute the vertical extent of the vertical scrollbar's thumb within the vertical range.

int computeVerticalScrollOffset()

Compute the vertical offset of the vertical scrollbar's thumb within the vertical range.

int computeVerticalScrollRange()

Compute the vertical range that the vertical scrollbar represents.

boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed)
Dispatch a fling to a nested scrolling parent.
boolean dispatchNestedPreFling(float velocityX, float velocityY)
Dispatch a fling to a nested scrolling parent before it is processed by this view.
boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow)
Dispatch one step of a nested scroll in progress before this view consumes any portion of it.
boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow)
Dispatch one step of a nested scroll in progress.
void draw(Canvas c)
Manually render this view (and all of its children) to the given Canvas.
boolean drawChild(Canvas canvas, View child, long drawingTime)
Draw one child of this View Group.
View findChildViewUnder(float x, float y)
Find the topmost view under the given point.
RecyclerView.ViewHolder findViewHolderForAdapterPosition(int position)
Return the ViewHolder for the item in the given position of the data set.
RecyclerView.ViewHolder findViewHolderForItemId(long id)
Return the ViewHolder for the item with the given id.
RecyclerView.ViewHolder findViewHolderForLayoutPosition(int position)
Return the ViewHolder for the item in the given position of the data set as of the latest layout pass.
RecyclerView.ViewHolder findViewHolderForPosition(int position)
boolean fling(int velocityX, int velocityY)
Begin a standard fling with an initial velocity along each axis in pixels per second.
View focusSearch(View focused, int direction)
Find the nearest view in the specified direction that wants to take focus.
ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs)
Returns a new set of layout parameters based on the supplied attributes set.
Adapter getAdapter()
Retrieves the previously set adapter or null if no adapter is set.
int getBaseline()

Return the offset of the RecyclerView's text baseline from the its top boundary.

int getChildAdapterPosition(View child)
Return the adapter position that the given child view corresponds to.
long getChildItemId(View child)
Return the stable item id that the given child view corresponds to.
int getChildLayoutPosition(View child)
Return the adapter position of the given child view as of the latest completed layout pass.
int getChildPosition(View child)
This method is deprecated. use getChildAdapterPosition(View) or getChildLayoutPosition(View).
RecyclerView.ViewHolder getChildViewHolder(View child)
Retrieve the RecyclerView.ViewHolder for the given child view.
RecyclerViewAccessibilityDelegate getCompatAccessibilityDelegate()
Returns the accessibility delegate compatibility implementation used by the RecyclerView.
RecyclerView.ItemAnimator getItemAnimator()
Gets the current ItemAnimator for this RecyclerView.
RecyclerView.LayoutManager getLayoutManager()
Return the RecyclerView.LayoutManager currently responsible for layout policy for this RecyclerView.
int getMaxFlingVelocity()
Returns the maximum fling velocity used by this RecyclerView.
int getMinFlingVelocity()
Returns the minimum velocity to start a fling.
RecyclerView.RecycledViewPool getRecycledViewPool()
Retrieve this RecyclerView's RecyclerView.RecycledViewPool.
int getScrollState()
Return the current scrolling state of the RecyclerView.
boolean hasFixedSize()
boolean hasNestedScrollingParent()
Returns true if this view has a nested scrolling parent.
boolean hasPendingAdapterUpdates()
Returns whether there are pending adapter updates which are not yet applied to the layout.
void invalidateItemDecorations()
Invalidates all ItemDecorations.
boolean isAnimating()
Returns true if RecyclerView is currently running some animations.
boolean isAttachedToWindow()
Returns true if RecyclerView is attached to window.
boolean isComputingLayout()
Returns whether RecyclerView is currently computing a layout.
boolean isLayoutFrozen()
Returns true if layout and scroll are frozen.
boolean isNestedScrollingEnabled()
Returns true if nested scrolling is enabled for this view.
void offsetChildrenHorizontal(int dx)
Offset the bounds of all child views by dx pixels.
void offsetChildrenVertical(int dy)
Offset the bounds of all child views by dy pixels.
void onChildAttachedToWindow(View child)
Called when an item view is attached to this RecyclerView.
void onChildDetachedFromWindow(View child)
Called when an item view is detached from this RecyclerView.
void onDraw(Canvas c)
Implement this to do your drawing.
boolean onGenericMotionEvent(MotionEvent event)
Implement this method to handle generic motion events.
boolean onInterceptTouchEvent(MotionEvent e)
Implement this method to intercept all touch screen motion events.
void onScrollStateChanged(int state)
Called when the scroll state of this RecyclerView changes.
void onScrolled(int dx, int dy)
Called when the scroll position of this RecyclerView changes.
boolean onTouchEvent(MotionEvent e)
Implement this method to handle touch screen motion events.
void removeItemDecoration(RecyclerView.ItemDecoration decor)
Remove an RecyclerView.ItemDecoration from this RecyclerView.
void removeOnChildAttachStateChangeListener(RecyclerView.OnChildAttachStateChangeListener listener)
Removes the provided listener from child attached state listeners list.
void removeOnItemTouchListener(RecyclerView.OnItemTouchListener listener)
void removeOnScrollListener(RecyclerView.OnScrollListener listener)
Remove a listener that was notified of any changes in scroll state or position.
void requestChildFocus(View child, View focused)
Called when a child of this parent wants focus
boolean requestChildRectangleOnScreen(View child, Rect rect, boolean immediate)
Called when a child of this group wants a particular rectangle to be positioned onto the screen.
void requestDisallowInterceptTouchEvent(boolean disallowIntercept)
Called when a child does not want this parent and its ancestors to intercept touch events with onInterceptTouchEvent(MotionEvent).
void requestLayout()
Call this when something has changed which has invalidated the layout of this view.
void scrollBy(int x, int y)
Move the scrolled position of your view.
void scrollTo(int x, int y)
Set the scrolled position of your view.
void scrollToPosition(int position)
Convenience method to scroll to a certain position.
void sendAccessibilityEventUnchecked(AccessibilityEvent event)
This method behaves exactly as sendAccessibilityEvent(int) but takes as an argument an empty AccessibilityEvent and does not perform a check whether accessibility is enabled.
void setAccessibilityDelegateCompat(RecyclerViewAccessibilityDelegate accessibilityDelegate)
Sets the accessibility delegate compatibility implementation used by RecyclerView.
void setAdapter(Adapter adapter)
Set a new adapter to provide child views on demand.
void setChildDrawingOrderCallback(RecyclerView.ChildDrawingOrderCallback childDrawingOrderCallback)
Sets the RecyclerView.ChildDrawingOrderCallback to be used for drawing children.
void setClipToPadding(boolean clipToPadding)
Sets whether this ViewGroup will clip its children to its padding and resize (but not clip) any EdgeEffect to the padded region, if padding is present.
void setHasFixedSize(boolean hasFixedSize)
RecyclerView can perform several optimizations if it can know in advance that changes in adapter content cannot change the size of the RecyclerView itself.
void setItemAnimator(RecyclerView.ItemAnimator animator)
Sets the RecyclerView.ItemAnimator that will handle animations involving changes to the items in this RecyclerView.
void setItemViewCacheSize(int size)
Set the number of offscreen views to retain before adding them to the potentially shared recycled view pool.
void setLayoutFrozen(boolean frozen)
Enable or disable layout and scroll.
void setLayoutManager(RecyclerView.LayoutManager layout)
Set the RecyclerView.LayoutManager that this RecyclerView will use.
void setNestedScrollingEnabled(boolean enabled)
Enable or disable nested scrolling for this view.
void setOnScrollListener(RecyclerView.OnScrollListener listener)
void setRecycledViewPool(RecyclerView.RecycledViewPool pool)
Recycled view pools allow multiple RecyclerViews to share a common pool of scrap views.
void setRecyclerListener(RecyclerView.RecyclerListener listener)
Register a listener that will be notified whenever a child view is recycled.
void setScrollingTouchSlop(int slopConstant)
Configure the scrolling touch slop for a specific use case.
void setViewCacheExtension(RecyclerView.ViewCacheExtension extension)
Sets a new RecyclerView.ViewCacheExtension to be used by the Recycler.
void smoothScrollBy(int dx, int dy)
Animate a scroll by the given amount of pixels along either axis.
void smoothScrollToPosition(int position)
Starts a smooth scroll to an adapter position.
boolean startNestedScroll(int axes)
Begin a nestable scroll operation along the given axes.
void stopNestedScroll()
Stop a nested scroll in progress.
void stopScroll()
Stop any current scroll in progress, such as one started by smoothScrollBy(int, int), fling(int, int) or a touch-initiated fling.
void swapAdapter(Adapter adapter, boolean removeAndRecycleExistingViews)
Swaps the current adapter with the provided one.
Protected Methods
boolean checkLayoutParams(ViewGroup.LayoutParams p)
void dispatchRestoreInstanceState(SparseArray<Parcelable> container)
Override to prevent thawing of any views created by the adapter.
void dispatchSaveInstanceState(SparseArray<Parcelable> container)
Override to prevent freezing of any views created by the adapter.
ViewGroup.LayoutParams generateDefaultLayoutParams()
Returns a set of default layout parameters.
ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p)
Returns a safe set of layout parameters based on the supplied layout params.
int getChildDrawingOrder(int childCount, int i)
Returns the index of the child to draw for this iteration.
void onAttachedToWindow()
This is called when the view is attached to a window.
void onDetachedFromWindow()
This is called when the view is detached from a window.
void onLayout(boolean changed, int l, int t, int r, int b)
Called from layout when this view should assign a size and position to each of its children.
void onMeasure(int widthSpec, int heightSpec)

Measure the view and its content to determine the measured width and the measured height.

void onRestoreInstanceState(Parcelable state)
Hook allowing a view to re-apply a representation of its internal state that had previously been generated by onSaveInstanceState().
Parcelable onSaveInstanceState()
Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state.
void onSizeChanged(int w, int h, int oldw, int oldh)
This is called during layout when the size of this view has changed.
void removeDetachedView(View child, boolean animate)
Finishes the removal of a detached view.
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Inherited Methods
From class android.view.ViewGroup
From class android.view.View
From class java.lang.Object
From interface android.view.ViewParent
From interface android.view.ViewManager
From interface android.graphics.drawable.Drawable.Callback
From interface android.view.KeyEvent.Callback
From interface android.view.accessibility.AccessibilityEventSource
From interface android.support.v4.view.ScrollingView
From interface android.support.v4.view.NestedScrollingChild

XML Attributes

android.support.v7.recyclerview:layoutManager

Class name of the Layout Manager to be used.

The class must extend android.support.v7.widget.RecyclerView$LayoutManager and have either a default constructor or constructor with the signature (android.content.Context, android.util.AttributeSet, int, int).

If the name starts with a '.', application package is prefixed. Else, if the name contains a '.', the classname is assumed to be a full class name. Else, the recycler view package name (android.support.v7.widget) is prefixed.

Must be a string value, using '\\;' to escape characters such as '\\n' or '\\uxxxx' for a unicode character.

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This is a private symbol.

Related Methods

Constants

public static final int HORIZONTAL

Constant Value: 0 (0x00000000)

public static final int INVALID_TYPE

Constant Value: -1 (0xffffffff)

public static final long NO_ID

Constant Value: -1 (0xffffffffffffffff)

public static final int NO_POSITION

Constant Value: -1 (0xffffffff)

public static final int SCROLL_STATE_DRAGGING

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

See Also
Constant Value: 1 (0x00000001)

public static final int SCROLL_STATE_IDLE

The RecyclerView is not currently scrolling.

See Also
Constant Value: 0 (0x00000000)

public static final int SCROLL_STATE_SETTLING

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

See Also
Constant Value: 2 (0x00000002)

public static final int TOUCH_SLOP_DEFAULT

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

Constant Value: 0 (0x00000000)

public static final int TOUCH_SLOP_PAGING

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.

Constant Value: 1 (0x00000001)

public static final int VERTICAL

Constant Value: 1 (0x00000001)

Public Constructors

public RecyclerView (Context context)

public RecyclerView (Context context, AttributeSet attrs)

public RecyclerView (Context context, AttributeSet attrs, int defStyle)

Public Methods

public void addFocusables (ArrayList<View> views, int direction, int focusableMode)

Adds any focusable views that are descendants of this view (possibly including this view if it is focusable itself) to views. This method adds all focusable views regardless if we are in touch mode or only views focusable in touch mode if we are in touch mode or only views that can take accessibility focus if accessibility is enabled depending on the focusable mode parameter.

Parameters
views Focusable views found so far or null if all we are interested is the number of focusables.
direction The direction of the focus.
focusableMode The type of focusables to be added.

public void addItemDecoration (RecyclerView.ItemDecoration decor)

Add an RecyclerView.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 Decoration to add

public void addItemDecoration (RecyclerView.ItemDecoration decor, int index)

Add an RecyclerView.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 Decoration to add
index Position in the decoration chain to insert this decoration at. If this value is negative the decoration will be added at the end.

public void addOnChildAttachStateChangeListener (RecyclerView.OnChildAttachStateChangeListener listener)

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 Listener to register

public void addOnItemTouchListener (RecyclerView.OnItemTouchListener listener)

Add an RecyclerView.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 onInterceptTouchEvent(RecyclerView, MotionEvent) its onTouchEvent(RecyclerView, MotionEvent) method will be called for each incoming MotionEvent until the end of the gesture.

Parameters
listener Listener to add

public void addOnScrollListener (RecyclerView.OnScrollListener listener)

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 listener to set or null to clear

public void clearOnChildAttachStateChangeListeners ()

public void clearOnScrollListeners ()

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

public int computeHorizontalScrollExtent ()

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 computeHorizontalScrollExtent(RecyclerView.State) in your LayoutManager.

Returns
  • The horizontal extent of the scrollbar's thumb

public int computeHorizontalScrollOffset ()

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 computeHorizontalScrollOffset(RecyclerView.State) in your LayoutManager.

Returns
  • The horizontal offset of the scrollbar's thumb

public int computeHorizontalScrollRange ()

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 computeHorizontalScrollRange(RecyclerView.State) in your LayoutManager.

Returns
  • The total horizontal range represented by the vertical scrollbar

public int computeVerticalScrollExtent ()

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 computeVerticalScrollExtent(RecyclerView.State) in your LayoutManager.

Returns
  • The vertical extent of the scrollbar's thumb

public int computeVerticalScrollOffset ()

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 computeVerticalScrollOffset(RecyclerView.State) in your LayoutManager.

Returns
  • The vertical offset of the scrollbar's thumb

public int computeVerticalScrollRange ()

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 computeVerticalScrollRange(RecyclerView.State) in your LayoutManager.

Returns
  • The total vertical range represented by the vertical scrollbar

public boolean dispatchNestedFling (float velocityX, float velocityY, boolean consumed)

Dispatch a fling to a nested scrolling parent.

This method should be used to indicate that a nested scrolling child has detected suitable conditions for a fling. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceeds the minimum fling velocity along a scrollable axis.

If a nested scrolling child view would normally fling but it is at the edge of its own content, it can use this method to delegate the fling to its nested scrolling parent instead. The parent may optionally consume the fling or observe a child fling.

Parameters
velocityX Horizontal fling velocity in pixels per second
velocityY Vertical fling velocity in pixels per second
consumed true if the child consumed the fling, false otherwise
Returns
  • true if the nested scrolling parent consumed or otherwise reacted to the fling

public boolean dispatchNestedPreFling (float velocityX, float velocityY)

Dispatch a fling to a nested scrolling parent before it is processed by this view.

Nested pre-fling events are to nested fling events what touch intercept is to touch and what nested pre-scroll is to nested scroll. dispatchNestedPreFling offsets an opportunity for the parent view in a nested fling to fully consume the fling before the child view consumes it. If this method returns true, a nested parent view consumed the fling and this view should not scroll as a result.

For a better user experience, only one view in a nested scrolling chain should consume the fling at a time. If a parent view consumed the fling this method will return false. Custom view implementations should account for this in two ways:

  • If a custom view is paged and needs to settle to a fixed page-point, do not call dispatchNestedPreFling; consume the fling and settle to a valid position regardless.
  • If a nested parent does consume the fling, this view should not scroll at all, even to settle back to a valid idle position.

Views should also not offer fling velocities to nested parent views along an axis where scrolling is not currently supported; a ScrollView should not offer a horizontal fling velocity to its parents since scrolling along that axis is not permitted and carrying velocity along that motion does not make sense.

Parameters
velocityX Horizontal fling velocity in pixels per second
velocityY Vertical fling velocity in pixels per second
Returns
  • true if a nested scrolling parent consumed the fling

public boolean dispatchNestedPreScroll (int dx, int dy, int[] consumed, int[] offsetInWindow)

Dispatch one step of a nested scroll in progress before this view consumes any portion of it.

Nested pre-scroll events are to nested scroll events what touch intercept is to touch. dispatchNestedPreScroll offers an opportunity for the parent view in a nested scrolling operation to consume some or all of the scroll operation before the child view consumes it.

Parameters
dx Horizontal scroll distance in pixels
dy Vertical scroll distance in pixels
consumed Output. If not null, consumed[0] will contain the consumed component of dx and consumed[1] the consumed dy.
offsetInWindow Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking.
Returns
  • true if the parent consumed some or all of the scroll delta

public boolean dispatchNestedScroll (int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow)

Dispatch one step of a nested scroll in progress.

Implementations of views that support nested scrolling should call this to report info about a scroll in progress to the current nested scrolling parent. If a nested scroll is not currently in progress or nested scrolling is not enabled for this view this method does nothing.

Compatible View implementations should also call dispatchNestedPreScroll before consuming a component of the scroll event themselves.

Parameters
dxConsumed Horizontal distance in pixels consumed by this view during this scroll step
dyConsumed Vertical distance in pixels consumed by this view during this scroll step
dxUnconsumed Horizontal scroll distance in pixels not consumed by this view
dyUnconsumed Horizontal scroll distance in pixels not consumed by this view
offsetInWindow Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking.
Returns
  • true if the event was dispatched, false if it could not be dispatched.

public void draw (Canvas c)

Manually render this view (and all of its children) to the given Canvas. The view must have already done a full layout before this function is called. When implementing a view, implement onDraw(android.graphics.Canvas) instead of overriding this method. If you do need to override this method, call the superclass version.

Parameters
c The Canvas to which the View is rendered.

public boolean drawChild (Canvas canvas, View child, long drawingTime)

Draw one child of this View Group. This method is responsible for getting the canvas in the right state. This includes clipping, translating so that the child's scrolled origin is at 0, 0, and applying any animation transformations.

Parameters
canvas The canvas on which to draw the child
child Who to draw
drawingTime The time at which draw is occurring
Returns
  • True if an invalidate() was issued

public View findChildViewUnder (float x, float y)

Find the topmost view under the given point.

Parameters
x Horizontal position in pixels to search
y Vertical position in pixels to search
Returns
  • The child view under (x, y) or null if no matching child is found

public RecyclerView.ViewHolder findViewHolderForAdapterPosition (int position)

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 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.

Parameters
position The position of the item in the data set of the adapter
Returns
  • The ViewHolder at position or null if there is no such item

public RecyclerView.ViewHolder findViewHolderForItemId (long id)

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.

Parameters
id The id for the requested item
Returns
  • The ViewHolder with the given id or null if there is no such item

public RecyclerView.ViewHolder findViewHolderForLayoutPosition (int position)

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 #getAdapterPosition() to get the current adapter position of a ViewHolder.

Parameters
position The position of the item in the data set of the adapter
Returns
  • The ViewHolder at position or null if there is no such item

public RecyclerView.ViewHolder findViewHolderForPosition (int position)

public boolean fling (int velocityX, int velocityY)

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 Initial horizontal velocity in pixels per second
velocityY Initial vertical velocity in pixels per second
Returns
  • 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.

public View focusSearch (View focused, int direction)

Find the nearest view in the specified direction that wants to take focus.

Parameters
focused The view that currently has focus
direction One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT, or 0 for not applicable.

public ViewGroup.LayoutParams generateLayoutParams (AttributeSet attrs)

Returns a new set of layout parameters based on the supplied attributes set.

Parameters
attrs the attributes to build the layout parameters from
Returns

public Adapter getAdapter ()

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

Returns
  • The previously set adapter

public int getBaseline ()

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.

Returns
  • the offset of the baseline within the RecyclerView's bounds or -1 if baseline alignment is not supported

public int getChildAdapterPosition (View child)

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

Parameters
child Child View to query
Returns
  • Adapter position corresponding to the given view or NO_POSITION

public long getChildItemId (View child)

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

Parameters
child Child View to query
Returns
  • Item id corresponding to the given view or NO_ID

public int getChildLayoutPosition (View child)

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 Child View to query
Returns
  • Adapter position of the given View as of last layout pass or NO_POSITION if the View is representing a removed item.

public int getChildPosition (View child)

This method is deprecated.
use getChildAdapterPosition(View) or getChildLayoutPosition(View).

public RecyclerView.ViewHolder getChildViewHolder (View child)

Retrieve the RecyclerView.ViewHolder for the given child view.

Parameters
child Child of this RecyclerView to query for its ViewHolder
Returns
  • The child view's ViewHolder

public RecyclerViewAccessibilityDelegate getCompatAccessibilityDelegate ()

Returns the accessibility delegate compatibility implementation used by the RecyclerView.

Returns
  • An instance of AccessibilityDelegateCompat used by RecyclerView

public RecyclerView.ItemAnimator getItemAnimator ()

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.

Returns
  • ItemAnimator The current ItemAnimator. If null, no animations will occur when changes occur to the items in this RecyclerView.

public RecyclerView.LayoutManager getLayoutManager ()

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

Returns
  • The currently bound LayoutManager

public int getMaxFlingVelocity ()

Returns the maximum fling velocity used by this RecyclerView.

Returns
  • The maximum fling velocity used by this RecyclerView.

public int getMinFlingVelocity ()

Returns the minimum velocity to start a fling.

Returns
  • The minimum velocity to start a fling

public RecyclerView.RecycledViewPool getRecycledViewPool ()

Retrieve this RecyclerView's RecyclerView.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.

Returns
  • The pool used to store recycled item views for reuse.

public int getScrollState ()

Return the current scrolling state of the RecyclerView.

public boolean hasFixedSize ()

Returns
  • true if the app has specified that changes in adapter content cannot change the size of the RecyclerView itself.

public boolean hasNestedScrollingParent ()

Returns true if this view has a nested scrolling parent.

The presence of a nested scrolling parent indicates that this view has initiated a nested scroll and it was accepted by an ancestor view further up the view hierarchy.

Returns
  • whether this view has a nested scrolling parent

public boolean hasPendingAdapterUpdates ()

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.

Returns
  • True if there are some adapter updates which are not yet reflected to layout or false if layout is up to date.

public void invalidateItemDecorations ()

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

public boolean isAnimating ()

Returns true if RecyclerView is currently running some animations.

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

Returns
  • True if there are some item animations currently running or waiting to be started.

public boolean isAttachedToWindow ()

Returns true if RecyclerView is attached to window.

public boolean isComputingLayout ()

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.

Returns
  • true if RecyclerView is currently computing a layout, false otherwise

public boolean isLayoutFrozen ()

Returns true if layout and scroll are frozen.

Returns
  • true if layout and scroll are frozen

public boolean isNestedScrollingEnabled ()

Returns true if nested scrolling is enabled for this view.

If nested scrolling is enabled and this View class implementation supports it, this view will act as a nested scrolling child view when applicable, forwarding data about the scroll operation in progress to a compatible and cooperating nested scrolling parent.

Returns
  • true if nested scrolling is enabled

public void offsetChildrenHorizontal (int dx)

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

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

public void offsetChildrenVertical (int dy)

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

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

public void onChildAttachedToWindow (View child)

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 RecyclerView.LayoutManager measures or lays out the view and is a good time to perform these changes.

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

public void onChildDetachedFromWindow (View child)

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 RecyclerView.LayoutManager fully detaches the child view from the parent and its window.

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

public void onDraw (Canvas c)

Implement this to do your drawing.

Parameters
c the canvas on which the background will be drawn

public boolean onGenericMotionEvent (MotionEvent event)

Implement this method to handle generic motion events.

Generic motion events describe joystick movements, mouse hovers, track pad touches, scroll wheel movements and other input events. The source of the motion event specifies the class of input that was received. Implementations of this method must examine the bits in the source before processing the event. The following code example shows how this is done.

Generic motion events with source class SOURCE_CLASS_POINTER are delivered to the view under the pointer. All other generic motion events are delivered to the focused view.

 public boolean onGenericMotionEvent(MotionEvent event) {
     if (event.isFromSource(InputDevice.SOURCE_CLASS_JOYSTICK)) {
         if (event.getAction() == MotionEvent.ACTION_MOVE) {
             // process the joystick movement...
             return true;
         }
     }
     if (event.isFromSource(InputDevice.SOURCE_CLASS_POINTER)) {
         switch (event.getAction()) {
             case MotionEvent.ACTION_HOVER_MOVE:
                 // process the mouse hover movement...
                 return true;
             case MotionEvent.ACTION_SCROLL:
                 // process the scroll wheel movement...
                 return true;
         }
     }
     return super.onGenericMotionEvent(event);
 }

Parameters
event The generic motion event being processed.
Returns
  • True if the event was handled, false otherwise.

public boolean onInterceptTouchEvent (MotionEvent e)

Implement this method to intercept all touch screen motion events. This allows you to watch events as they are dispatched to your children, and take ownership of the current gesture at any point.

Using this function takes some care, as it has a fairly complicated interaction with View.onTouchEvent(MotionEvent), and using it requires implementing that method as well as this one in the correct way. Events will be received in the following order:

  1. You will receive the down event here.
  2. The down event will be handled either by a child of this view group, or given to your own onTouchEvent() method to handle; this means you should implement onTouchEvent() to return true, so you will continue to see the rest of the gesture (instead of looking for a parent view to handle it). Also, by returning true from onTouchEvent(), you will not receive any following events in onInterceptTouchEvent() and all touch processing must happen in onTouchEvent() like normal.
  3. For as long as you return false from this function, each following event (up to and including the final up) will be delivered first here and then to the target's onTouchEvent().
  4. If you return true from here, you will not receive any following events: the target view will receive the same event but with the action ACTION_CANCEL, and all further events will be delivered to your onTouchEvent() method and no longer appear here.

Parameters
e The motion event being dispatched down the hierarchy.
Returns
  • Return true to steal motion events from the children and have them dispatched to this ViewGroup through onTouchEvent(). The current target will receive an ACTION_CANCEL event, and no further messages will be delivered here.

public void onScrollStateChanged (int state)

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 the new scroll state, one of SCROLL_STATE_IDLE, SCROLL_STATE_DRAGGING or SCROLL_STATE_SETTLING

public void onScrolled (int dx, int dy)

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 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 getScrollX() and 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 horizontal distance scrolled in pixels
dy vertical distance scrolled in pixels

public boolean onTouchEvent (MotionEvent e)

Implement this method to handle touch screen motion events.

If this method is used to detect click actions, it is recommended that the actions be performed by implementing and calling performClick(). This will ensure consistent system behavior, including:

  • obeying click sound preferences
  • dispatching OnClickListener calls
  • handling ACTION_CLICK when accessibility features are enabled

Parameters
e The motion event.
Returns
  • True if the event was handled, false otherwise.

public void removeItemDecoration (RecyclerView.ItemDecoration decor)

Remove an RecyclerView.ItemDecoration from this RecyclerView.

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

Parameters
decor Decoration to remove

public void removeOnChildAttachStateChangeListener (RecyclerView.OnChildAttachStateChangeListener listener)

Removes the provided listener from child attached state listeners list.

Parameters
listener Listener to unregister

public void removeOnItemTouchListener (RecyclerView.OnItemTouchListener listener)

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

Parameters
listener Listener to remove

public void removeOnScrollListener (RecyclerView.OnScrollListener listener)

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

Parameters
listener listener to set or null to clear

public void requestChildFocus (View child, View focused)

Called when a child of this parent wants focus

Parameters
child The child of this ViewParent that wants focus. This view will contain the focused view. It is not necessarily the view that actually has focus.
focused The view that is a descendant of child that actually has focus

public boolean requestChildRectangleOnScreen (View child, Rect rect, boolean immediate)

Called when a child of this group wants a particular rectangle to be positioned onto the screen. ViewGroups overriding this can trust that:

  • child will be a direct child of this group
  • rectangle will be in the child's coordinates

ViewGroups overriding this should uphold the contract:

  • nothing will change if the rectangle is already visible
  • the view port will be scrolled only just enough to make the rectangle visible
Parameters
child The direct child making the request.
rect The rectangle in the child's coordinates the child wishes to be on the screen.
immediate True to forbid animated or delayed scrolling, false otherwise
Returns
  • Whether the group scrolled to handle the operation

public void requestDisallowInterceptTouchEvent (boolean disallowIntercept)

Called when a child does not want this parent and its ancestors to intercept touch events with onInterceptTouchEvent(MotionEvent).

This parent should pass this call onto its parents. This parent must obey this request for the duration of the touch (that is, only clear the flag after this parent has received an up or a cancel.

Parameters
disallowIntercept True if the child does not want the parent to intercept touch events.

public void requestLayout ()

Call this when something has changed which has invalidated the layout of this view. This will schedule a layout pass of the view tree. This should not be called while the view hierarchy is currently in a layout pass (isInLayout(). If layout is happening, the request may be honored at the end of the current layout pass (and then layout will run again) or after the current frame is drawn and the next layout occurs.

Subclasses which override this method should call the superclass method to handle possible request-during-layout errors correctly.

public void scrollBy (int x, int y)

Move the scrolled position of your view. This will cause a call to onScrollChanged(int, int, int, int) and the view will be invalidated.

Parameters
x the amount of pixels to scroll by horizontally
y the amount of pixels to scroll by vertically

public void scrollTo (int x, int y)

Set the scrolled position of your view. This will cause a call to onScrollChanged(int, int, int, int) and the view will be invalidated.

Parameters
x the x position to scroll to
y the y position to scroll to

public void scrollToPosition (int position)

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

Parameters
position Scroll to this adapter position

public void sendAccessibilityEventUnchecked (AccessibilityEvent event)

This method behaves exactly as sendAccessibilityEvent(int) but takes as an argument an empty AccessibilityEvent and does not perform a check whether accessibility is enabled.

If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its sendAccessibilityEventUnchecked(View, AccessibilityEvent) is responsible for handling this call.

Parameters
event The event to send.

public void setAccessibilityDelegateCompat (RecyclerViewAccessibilityDelegate accessibilityDelegate)

Sets the accessibility delegate compatibility implementation used by RecyclerView.

Parameters
accessibilityDelegate The accessibility delegate to be used by RecyclerView.

public void setAdapter (Adapter adapter)

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 The new adapter to set, or null to set no adapter.

public void setChildDrawingOrderCallback (RecyclerView.ChildDrawingOrderCallback childDrawingOrderCallback)

Sets the RecyclerView.ChildDrawingOrderCallback to be used for drawing children.

See getChildDrawingOrder(int, int) for details. Calling this method will always call 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 The ChildDrawingOrderCallback to be used by the drawing system.

public void setClipToPadding (boolean clipToPadding)

Sets whether this ViewGroup 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 ViewGroup. This clipping behavior is only enabled if padding is non-zero.

Parameters
clipToPadding true to clip children to the padding of the group, and resize (but not clip) any EdgeEffect to the padded region. False otherwise.

public void setHasFixedSize (boolean hasFixedSize)

RecyclerView can perform several optimizations if it can know in advance that changes in adapter content cannot change the size of the RecyclerView itself. If your use of RecyclerView falls into this category, set this to true.

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

public void setItemAnimator (RecyclerView.ItemAnimator animator)

Sets the RecyclerView.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 The ItemAnimator being set. If null, no animations will occur when changes occur to the items in this RecyclerView.

public void setItemViewCacheSize (int size)

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 Number of views to cache offscreen before returning them to the general recycled view pool

public void setLayoutFrozen (boolean frozen)

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; onFocusSearchFailed(View, int, Recycler, State) will not be called.

setLayoutFrozen(true) does not prevent app from directly calling scrollToPosition(int), 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 true to freeze layout and scroll, false to re-enable.

public void setLayoutManager (RecyclerView.LayoutManager layout)

Set the RecyclerView.LayoutManager that this RecyclerView will use.

In contrast to other adapter-backed views such as ListView or GridView, RecyclerView allows client code to provide custom layout arrangements for child views. These arrangements are controlled by the RecyclerView.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 LayoutManager to use

public void setNestedScrollingEnabled (boolean enabled)

Enable or disable nested scrolling for this view.

If this property is set to true the view will be permitted to initiate nested scrolling operations with a compatible parent view in the current hierarchy. If this view does not implement nested scrolling this will have no effect. Disabling nested scrolling while a nested scroll is in progress has the effect of stopping the nested scroll.

Parameters
enabled true to enable nested scrolling, false to disable

public void setOnScrollListener (RecyclerView.OnScrollListener listener)

This method is deprecated.
Use addOnScrollListener(OnScrollListener) and removeOnScrollListener(OnScrollListener)

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

Parameters
listener Listener to set or null to clear

public void setRecycledViewPool (RecyclerView.RecycledViewPool pool)

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 ViewPager.

Parameters
pool Pool to set. If this parameter is null a new pool will be created and used.

public void setRecyclerListener (RecyclerView.RecyclerListener listener)

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 Listener to register, or null to clear

public void setScrollingTouchSlop (int slopConstant)

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 One of the TOUCH_SLOP_ constants representing the intended usage of this RecyclerView

public void setViewCacheExtension (RecyclerView.ViewCacheExtension extension)

Sets a new RecyclerView.ViewCacheExtension to be used by the Recycler.

Parameters
extension ViewCacheExtension to be used or null if you want to clear the existing one.

public void smoothScrollBy (int dx, int dy)

Animate a scroll by the given amount of pixels along either axis.

Parameters
dx Pixels to scroll horizontally
dy Pixels to scroll vertically

public void smoothScrollToPosition (int position)

Starts a smooth scroll to an adapter position.

To support smooth scrolling, you must override smoothScrollToPosition(RecyclerView, State, int) and create a RecyclerView.SmoothScroller.

RecyclerView.LayoutManager is responsible for creating the actual scroll action. If you want to provide a custom smooth scroll logic, override smoothScrollToPosition(RecyclerView, State, int) in your LayoutManager.

Parameters
position The adapter position to scroll to

public boolean startNestedScroll (int axes)

Begin a nestable scroll operation along the given axes.

A view starting a nested scroll promises to abide by the following contract:

The view will call startNestedScroll upon initiating a scroll operation. In the case of a touch scroll this corresponds to the initial ACTION_DOWN. In the case of touch scrolling the nested scroll will be terminated automatically in the same manner as requestDisallowInterceptTouchEvent(boolean). In the event of programmatic scrolling the caller must explicitly call stopNestedScroll() to indicate the end of the nested scroll.

If startNestedScroll returns true, a cooperative parent was found. If it returns false the caller may ignore the rest of this contract until the next scroll. Calling startNestedScroll while a nested scroll is already in progress will return true.

At each incremental step of the scroll the caller should invoke dispatchNestedPreScroll once it has calculated the requested scrolling delta. If it returns true the nested scrolling parent at least partially consumed the scroll and the caller should adjust the amount it scrolls by.

After applying the remainder of the scroll delta the caller should invoke dispatchNestedScroll, passing both the delta consumed and the delta unconsumed. A nested scrolling parent may treat these values differently. See onNestedScroll(View, int, int, int, int).

Parameters
axes Flags consisting of a combination of SCROLL_AXIS_HORIZONTAL and/or SCROLL_AXIS_VERTICAL.
Returns
  • true if a cooperative parent was found and nested scrolling has been enabled for the current gesture.

public void stopNestedScroll ()

Stop a nested scroll in progress.

Calling this method when a nested scroll is not currently in progress is harmless.

public void stopScroll ()

Stop any current scroll in progress, such as one started by smoothScrollBy(int, int), fling(int, int) or a touch-initiated fling.

public void swapAdapter (Adapter adapter, boolean removeAndRecycleExistingViews)

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 RecyclerView.ViewHolder and does not clear the RecycledViewPool.

Note that it still calls onAdapterChanged callbacks.

Parameters
adapter The new adapter to set, or null to set no adapter.
removeAndRecycleExistingViews 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.

Protected Methods

protected boolean checkLayoutParams (ViewGroup.LayoutParams p)

protected void dispatchRestoreInstanceState (SparseArray<Parcelable> container)

Override to prevent thawing of any views created by the adapter.

Parameters
container The SparseArray which holds previously saved state.

protected void dispatchSaveInstanceState (SparseArray<Parcelable> container)

Override to prevent freezing of any views created by the adapter.

Parameters
container The SparseArray in which to save the view's state.

protected ViewGroup.LayoutParams generateDefaultLayoutParams ()

Returns a set of default layout parameters. These parameters are requested when the View passed to addView(View) has no layout parameters already set. If null is returned, an exception is thrown from addView.

Returns
  • a set of default layout parameters or null

protected ViewGroup.LayoutParams generateLayoutParams (ViewGroup.LayoutParams p)

Returns a safe set of layout parameters based on the supplied layout params. When a ViewGroup is passed a View whose layout params do not pass the test of checkLayoutParams(android.view.ViewGroup.LayoutParams), this method is invoked. This method should return a new set of layout params suitable for this ViewGroup, possibly by copying the appropriate attributes from the specified set of layout params.

Parameters
p The layout parameters to convert into a suitable set of layout parameters for this ViewGroup.
Returns

protected int getChildDrawingOrder (int childCount, int i)

Returns the index of the child to draw for this iteration. Override this if you want to change the drawing order of children. By default, it returns i.

NOTE: In order for this method to be called, you must enable child ordering first by calling setChildrenDrawingOrderEnabled(boolean).

Parameters
i The current iteration.
Returns
  • The index of the child to draw this iteration.

protected void onAttachedToWindow ()

This is called when the view is attached to a window. At this point it has a Surface and will start drawing. Note that this function is guaranteed to be called before onDraw(android.graphics.Canvas), however it may be called any time before the first onDraw -- including before or after onMeasure(int, int).

protected void onDetachedFromWindow ()

This is called when the view is detached from a window. At this point it no longer has a surface for drawing.

protected void onLayout (boolean changed, int l, int t, int r, int b)

Called from layout when this view should assign a size and position to each of its children. Derived classes with children should override this method and call layout on each of their children.

Parameters
changed This is a new size or position for this view
l Left position, relative to parent
t Top position, relative to parent
r Right position, relative to parent
b Bottom position, relative to parent

protected void onMeasure (int widthSpec, int heightSpec)

Measure the view and its content to determine the measured width and the measured height. This method is invoked by measure(int, int) and should be overridden by subclasses to provide accurate and efficient measurement of their contents.

CONTRACT: When overriding this method, you must call setMeasuredDimension(int, int) to store the measured width and height of this view. Failure to do so will trigger an IllegalStateException, thrown by measure(int, int). Calling the superclass' onMeasure(int, int) is a valid use.

The base class implementation of measure defaults to the background size, unless a larger size is allowed by the MeasureSpec. Subclasses should override onMeasure(int, int) to provide better measurements of their content.

If this method is overridden, it is the subclass's responsibility to make sure the measured height and width are at least the view's minimum height and width (getSuggestedMinimumHeight() and getSuggestedMinimumWidth()).

Parameters
widthSpec horizontal space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.
heightSpec vertical space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.

protected void onRestoreInstanceState (Parcelable state)

Hook allowing a view to re-apply a representation of its internal state that had previously been generated by onSaveInstanceState(). This function will never be called with a null state.

Parameters
state The frozen state that had previously been returned by onSaveInstanceState().

protected Parcelable onSaveInstanceState ()

Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state. This state should only contain information that is not persistent or can not be reconstructed later. For example, you will never store your current position on screen because that will be computed again when a new instance of the view is placed in its view hierarchy.

Some examples of things you may store here: the current cursor position in a text view (but usually not the text itself since that is stored in a content provider or other persistent storage), the currently selected item in a list view.

Returns
  • Returns a Parcelable object containing the view's current dynamic state, or null if there is nothing interesting to save. The default implementation returns null.

protected void onSizeChanged (int w, int h, int oldw, int oldh)

This is called during layout when the size of this view has changed. If you were just added to the view hierarchy, you're called with the old values of 0.

Parameters
w Current width of this view.
h Current height of this view.
oldw Old width of this view.
oldh Old height of this view.

protected void removeDetachedView (View child, boolean animate)

Finishes the removal of a detached view. This method will dispatch the detached from window event and notify the hierarchy change listener.

This method is intended to be lightweight and makes no assumptions about whether the parent or child should be redrawn. Proper use of this method will include also making any appropriate requestLayout() or invalidate() calls. For example, callers can post a Runnable which performs a requestLayout() on the next frame, after all detach/remove calls are finished, causing layout to be run prior to redrawing the view hierarchy.

Parameters
child the child to be definitely removed from the view hierarchy
animate if true and the view has an animation, the view is placed in the disappearing views list, otherwise, it is detached from the window