Android APIs
public class

RecyclerView

extends ViewGroup
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.

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
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.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.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. 
[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 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 draw(Canvas c)
Manually render this view (and all of its children) to the given Canvas.
View findChildViewUnder(float x, float y)
Find the topmost view under the given point.
RecyclerView.ViewHolder findViewHolderForItemId(long id)
Return the ViewHolder for the item with the given id.
RecyclerView.ViewHolder findViewHolderForPosition(int position)
Return the ViewHolder for the item in the given position of the data set.
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.
long getChildItemId(View child)
Return the stable item id that the given child view corresponds to.
int getChildPosition(View child)
Return the adapter position that the given child view corresponds to.
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.
RecyclerView.RecycledViewPool getRecycledViewPool()
Retrieve this RecyclerView's RecyclerView.RecycledViewPool.
int getScrollState()
Return the current scrolling state of the RecyclerView.
boolean hasFixedSize()
void invalidateItemDecorations()
Invalidates all ItemDecorations.
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 onInterceptTouchEvent(MotionEvent e)
Implement this method to intercept all touch screen motion events.
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 removeOnItemTouchListener(RecyclerView.OnItemTouchListener listener)
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 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 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 setClipToPadding(boolean clipToPadding)
By default, children are clipped to the padding of the ViewGroup.
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 setLayoutManager(RecyclerView.LayoutManager layout)
Set the RecyclerView.LayoutManager that this RecyclerView will use.
void setOnScrollListener(RecyclerView.OnScrollListener listener)
Set a listener that will be notified of any changes in scroll state or position.
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.
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)
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.

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.
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.
[Expand]
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

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 enabeld depending on the focusable mode paramater.

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 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 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 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 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.

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

public RecyclerView.ViewHolder findViewHolderForPosition (int position)

Return the ViewHolder for the item in the given position of the data set.

Parameters
position The position of the item in the data set of the adapter
Returns
  • The ViewHolder at 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

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 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 getChildPosition (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 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 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 void invalidateItemDecorations ()

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

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 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 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 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 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 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 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 setClipToPadding (boolean clipToPadding)

By default, children are clipped to the padding of the ViewGroup. This allows view groups to override this behavior

Parameters
clipToPadding true to clip children to the padding of the group, 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 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 setOnScrollListener (RecyclerView.OnScrollListener listener)

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 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 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

protected 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

protected 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

protected 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

protected 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

protected 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

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 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 overriden 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