RecyclerView.LayoutManager

public static abstract class RecyclerView.LayoutManager
extends Object

java.lang.Object
   ↳ androidx.recyclerview.widget.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. By changing the LayoutManager a RecyclerView can be used to implement a standard vertically scrolling list, a uniform grid, staggered grids, horizontally scrolling collections and more. Several stock layout managers are provided for general use.

If the LayoutManager specifies a default constructor or one with the signature (Context, AttributeSet, int, int), RecyclerView will instantiate and set the LayoutManager when being inflated. Most used properties can be then obtained from getProperties(Context, AttributeSet, int, int). In case a LayoutManager specifies both constructors, the non-default constructor will take precedence.

Summary

Nested classes

interface RecyclerView.LayoutManager.LayoutPrefetchRegistry

Interface for LayoutManagers to request items to be prefetched, based on position, with specified distance from viewport, which indicates priority. 

class RecyclerView.LayoutManager.Properties

Some general properties that a LayoutManager may want to use. 

Public constructors

LayoutManager()

Public methods

void addDisappearingView(View child, int index)

To be called only during onLayoutChildren(Recycler, State) to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

void addDisappearingView(View child)

To be called only during onLayoutChildren(Recycler, State) to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

void addView(View child, int index)

Add a view to the currently attached RecyclerView if needed.

void addView(View child)

Add a view to the currently attached RecyclerView if needed.

void assertInLayoutOrScroll(String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is not.

void assertNotInLayoutOrScroll(String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is.

void attachView(View child)

Reattach a previously detached view.

void attachView(View child, int index, RecyclerView.LayoutParams lp)

Reattach a previously detached view.

void attachView(View child, int index)

Reattach a previously detached view.

void calculateItemDecorationsForChild(View child, Rect outRect)

Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.

boolean canScrollHorizontally()

Query if horizontal scrolling is currently supported.

boolean canScrollVertically()

Query if vertical scrolling is currently supported.

boolean checkLayoutParams(RecyclerView.LayoutParams lp)

Determines the validity of the supplied LayoutParams object.

static int chooseSize(int spec, int desired, int min)

Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.

void collectAdjacentPrefetchPositions(int dx, int dy, RecyclerView.State state, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)

Gather all positions from the LayoutManager to be prefetched, given specified momentum.

void collectInitialPrefetchPositions(int adapterItemCount, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)

Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView.

int computeHorizontalScrollExtent(RecyclerView.State state)

Override this method if you want to support scroll bars.

int computeHorizontalScrollOffset(RecyclerView.State state)

Override this method if you want to support scroll bars.

int computeHorizontalScrollRange(RecyclerView.State state)

Override this method if you want to support scroll bars.

int computeVerticalScrollExtent(RecyclerView.State state)

Override this method if you want to support scroll bars.

int computeVerticalScrollOffset(RecyclerView.State state)

Override this method if you want to support scroll bars.

int computeVerticalScrollRange(RecyclerView.State state)

Override this method if you want to support scroll bars.

void detachAndScrapAttachedViews(RecyclerView.Recycler recycler)

Temporarily detach and scrap all currently attached child views.

void detachAndScrapView(View child, RecyclerView.Recycler recycler)

Detach a child view and add it to a Recycler's scrap heap.

void detachAndScrapViewAt(int index, RecyclerView.Recycler recycler)

Detach a child view and add it to a Recycler's scrap heap.

void detachView(View child)

Temporarily detach a child view.

void detachViewAt(int index)

Temporarily detach a child view.

void endAnimation(View view)

Ends all animations on the view created by the RecyclerView.ItemAnimator.

View findContainingItemView(View view)

Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.

View findViewByPosition(int position)

Finds the view which represents the given adapter position.

abstract RecyclerView.LayoutParams generateDefaultLayoutParams()

Create a default LayoutParams object for a child of the RecyclerView.

RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs)

Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.

RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp)

Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.

int getBaseline()

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

int getBottomDecorationHeight(View child)

Returns the total height of item decorations applied to child's bottom.

View getChildAt(int index)

Return the child view at the given index

int getChildCount()

Return the current number of child views attached to the parent RecyclerView.

static int getChildMeasureSpec(int parentSize, int parentMode, int padding, int childDimension, boolean canScroll)

Calculate a MeasureSpec value for measuring a child view in one dimension.

static int getChildMeasureSpec(int parentSize, int padding, int childDimension, boolean canScroll)

This method is deprecated. use getChildMeasureSpec(int, int, int, int, boolean)

boolean getClipToPadding()

Check if the RecyclerView is configured to clip child views to its padding.

int getColumnCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)

Returns the number of columns for accessibility.

int getDecoratedBottom(View child)

Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations.

void getDecoratedBoundsWithMargins(View view, Rect outBounds)

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

int getDecoratedLeft(View child)

Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations.

int getDecoratedMeasuredHeight(View child)

Returns the measured height of the given child, plus the additional size of any insets applied by ItemDecorations.

int getDecoratedMeasuredWidth(View child)

Returns the measured width of the given child, plus the additional size of any insets applied by ItemDecorations.

int getDecoratedRight(View child)

Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations.

int getDecoratedTop(View child)

Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations.

View getFocusedChild()

Returns the item View which has or contains focus.

int getHeight()

Returns the height that is currently relevant to the LayoutManager.

int getHeightMode()

Return the height measurement spec mode that is currently relevant to the LayoutManager.

int getItemCount()

Returns the number of items in the adapter bound to the parent RecyclerView.

int getItemViewType(View view)

Returns the View type defined by the adapter.

int getLayoutDirection()

Returns the resolved layout direction for this RecyclerView.

int getLeftDecorationWidth(View child)

Returns the total width of item decorations applied to child's left.

int getMinimumHeight()
int getMinimumWidth()
int getPaddingBottom()

Return the bottom padding of the parent RecyclerView

int getPaddingEnd()

Return the end padding of the parent RecyclerView

int getPaddingLeft()

Return the left padding of the parent RecyclerView

int getPaddingRight()

Return the right padding of the parent RecyclerView

int getPaddingStart()

Return the start padding of the parent RecyclerView

int getPaddingTop()

Return the top padding of the parent RecyclerView

int getPosition(View view)

Returns the adapter position of the item represented by the given View.

static RecyclerView.LayoutManager.Properties getProperties(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)

Parse the xml attributes to get the most common properties used by layout managers.

int getRightDecorationWidth(View child)

Returns the total width of item decorations applied to child's right.

int getRowCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)

Returns the number of rows for accessibility.

int getSelectionModeForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)

Returns the selection mode for accessibility.

int getTopDecorationHeight(View child)

Returns the total height of item decorations applied to child's top.

void getTransformedBoundingBox(View child, boolean includeDecorInsets, Rect out)

Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.

int getWidth()

Returns the width that is currently relevant to the LayoutManager.

int getWidthMode()

Return the width measurement spec mode that is currently relevant to the LayoutManager.

boolean hasFocus()

Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.

void ignoreView(View view)

Flags a view so that it will not be scrapped or recycled.

boolean isAttachedToWindow()

Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.

boolean isAutoMeasureEnabled()

Returns whether the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or if it should be done by the LayoutManager's implementation of onMeasure(Recycler, State, int, int).

boolean isFocused()

Returns true if the RecyclerView this LayoutManager is bound to has focus.

final boolean isItemPrefetchEnabled()

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

boolean isLayoutHierarchical(RecyclerView.Recycler recycler, RecyclerView.State state)

Returns whether layout is hierarchical or not to be used for accessibility.

boolean isMeasurementCacheEnabled()

In addition to the View Framework's measurement cache, RecyclerView uses its own additional measurement cache for its children to avoid re-measuring them when not necessary.

boolean isSmoothScrolling()
boolean isViewPartiallyVisible(View child, boolean completelyVisible, boolean acceptEndPointInclusion)

Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters.

void layoutDecorated(View child, int left, int top, int right, int bottom)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations.

void layoutDecoratedWithMargins(View child, int left, int top, int right, int bottom)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations and margins.

void measureChild(View child, int widthUsed, int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.

void measureChildWithMargins(View child, int widthUsed, int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account.

void moveView(int fromIndex, int toIndex)

Moves a View from one position to another.

void offsetChildrenHorizontal(int dx)

Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.

void offsetChildrenVertical(int dy)

Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.

void onAdapterChanged(Adapter oldAdapter, Adapter newAdapter)

Called if the RecyclerView this LayoutManager is bound to has a different adapter set via RecyclerView.setAdapter(Adapter) or RecyclerView.swapAdapter(Adapter, boolean).

boolean onAddFocusables(RecyclerView recyclerView, ArrayList<View> views, int direction, int focusableMode)

Called to populate focusable views within the RecyclerView.

void onAttachedToWindow(RecyclerView view)

Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.

void onDetachedFromWindow(RecyclerView view)

This method is deprecated. override onDetachedFromWindow(RecyclerView, Recycler)

void onDetachedFromWindow(RecyclerView view, RecyclerView.Recycler recycler)

Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.

View onFocusSearchFailed(View focused, int direction, RecyclerView.Recycler recycler, RecyclerView.State state)

Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.

void onInitializeAccessibilityEvent(AccessibilityEvent event)
void onInitializeAccessibilityEvent(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityEvent event)

Called by the accessibility delegate to initialize an accessibility event.

void onInitializeAccessibilityNodeInfo(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityNodeInfoCompat info)

Called by the AccessibilityDelegate when the information about the current layout should be populated.

void onInitializeAccessibilityNodeInfoForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View host, AccessibilityNodeInfoCompat info)

Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated.

View onInterceptFocusSearch(View focused, int direction)

This method gives a LayoutManager an opportunity to intercept the initial focus search before the default behavior of FocusFinder is used.

void onItemsAdded(RecyclerView recyclerView, int positionStart, int itemCount)

Called when items have been added to the adapter.

void onItemsChanged(RecyclerView recyclerView)

Called in response to a call to RecyclerView.Adapter.notifyDataSetChanged() or RecyclerView.swapAdapter(Adapter, boolean) ()} and signals that the the entire data set has changed.

void onItemsMoved(RecyclerView recyclerView, int from, int to, int itemCount)

Called when an item is moved withing the adapter.

void onItemsRemoved(RecyclerView recyclerView, int positionStart, int itemCount)

Called when items have been removed from the adapter.

void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount)

Called when items have been changed in the adapter.

void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount, Object payload)

Called when items have been changed in the adapter and with optional payload.

void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)

Lay out all relevant child views from the given adapter.

void onLayoutCompleted(RecyclerView.State state)

Called after a full layout calculation is finished.

void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec)

Measure the attached RecyclerView.

boolean onRequestChildFocus(RecyclerView parent, View child, View focused)

This method is deprecated. Use onRequestChildFocus(RecyclerView, State, View, View)

boolean onRequestChildFocus(RecyclerView parent, RecyclerView.State state, View child, View focused)

Called when a descendant view of the RecyclerView requests focus.

void onRestoreInstanceState(Parcelable state)

Called when the RecyclerView is ready to restore the state based on a previous RecyclerView.

Parcelable onSaveInstanceState()

Called when the LayoutManager should save its state.

void onScrollStateChanged(int state)

RecyclerView calls this method to notify LayoutManager that scroll state has changed.

boolean performAccessibilityAction(RecyclerView.Recycler recycler, RecyclerView.State state, int action, Bundle args)

Called by AccessibilityDelegate when an action is requested from the RecyclerView.

boolean performAccessibilityActionForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View view, int action, Bundle args)

Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager.

void postOnAnimation(Runnable action)

Causes the Runnable to execute on the next animation time step.

void removeAllViews()

Remove all views from the currently attached RecyclerView.

void removeAndRecycleAllViews(RecyclerView.Recycler recycler)

Removes all views and recycles them using the given recycler.

void removeAndRecycleView(View child, RecyclerView.Recycler recycler)

Remove a child view and recycle it using the given Recycler.

void removeAndRecycleViewAt(int index, RecyclerView.Recycler recycler)

Remove a child view and recycle it using the given Recycler.

boolean removeCallbacks(Runnable action)

Removes the specified Runnable from the message queue.

void removeDetachedView(View child)

Finish removing a view that was previously temporarily detached.

void removeView(View child)

Remove a view from the currently attached RecyclerView if needed.

void removeViewAt(int index)

Remove a view from the currently attached RecyclerView if needed.

boolean requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect, boolean immediate, boolean focusedChildVisible)

Requests that the given child of the RecyclerView be positioned onto the screen.

boolean requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect, boolean immediate)

Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen.

void requestLayout()

Calls RecyclerView#requestLayout on the underlying RecyclerView

void requestSimpleAnimationsInNextLayout()

A LayoutManager can call this method to force RecyclerView to run simple animations in the next layout pass, even if there is not any trigger to do so.

int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state)

Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.

void scrollToPosition(int position)

Scroll to the specified adapter position.

int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state)

Scroll vertically by dy pixels in screen coordinates and return the distance traveled.

void setAutoMeasureEnabled(boolean enabled)

This method is deprecated. Implementors of LayoutManager should define whether or not it uses AutoMeasure by overriding isAutoMeasureEnabled().

final void setItemPrefetchEnabled(boolean enabled)

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

void setMeasuredDimension(int widthSize, int heightSize)

Set the measured dimensions of the host RecyclerView.

void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)

Sets the measured dimensions from the given bounding box of the children and the measurement specs that were passed into RecyclerView.onMeasure(int, int).

void setMeasurementCacheEnabled(boolean measurementCacheEnabled)

Sets whether RecyclerView should use its own measurement cache for the children.

void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position)

Smooth scroll to the specified adapter position.

void startSmoothScroll(RecyclerView.SmoothScroller smoothScroller)

Starts a smooth scroll using the provided RecyclerView.SmoothScroller.

void stopIgnoringView(View view)

View can be scrapped and recycled again.

boolean supportsPredictiveItemAnimations()

Returns whether this LayoutManager supports "predictive item animations".

Inherited methods

Public constructors

LayoutManager

public LayoutManager ()

Public methods

addDisappearingView

public void addDisappearingView (View child, 
                int index)

To be called only during onLayoutChildren(Recycler, State) to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

Views added via this method are going to be invisible to LayoutManager after the dispatchLayout pass is complete. They cannot be retrieved via getChildAt(int) or won't be included in getChildCount() method.

Parameters
child View: View to add and then remove with animation.

index int: Index of the view.

addDisappearingView

public void addDisappearingView (View child)

To be called only during onLayoutChildren(Recycler, State) to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

Views added via this method are going to be invisible to LayoutManager after the dispatchLayout pass is complete. They cannot be retrieved via getChildAt(int) or won't be included in getChildCount() method.

Parameters
child View: View to add and then remove with animation.

addView

public void addView (View child, 
                int index)

Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a RecyclerView.Recycler using RecyclerView.Recycler.getViewForPosition(int).

Parameters
child View: View to add

index int: Index to add child at

addView

public void addView (View child)

Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a RecyclerView.Recycler using RecyclerView.Recycler.getViewForPosition(int).

Parameters
child View: View to add

assertInLayoutOrScroll

public void assertInLayoutOrScroll (String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is not.

Parameters
message String: The message for the exception. Can be null.

assertNotInLayoutOrScroll

public void assertNotInLayoutOrScroll (String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is.

Parameters
message String: The message for the exception. Can be null.

attachView

public void attachView (View child)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView(android.view.View, RecyclerView.Recycler) scrapped}.

Parameters
child View: Child to reattach

attachView

public void attachView (View child, 
                int index, 
                RecyclerView.LayoutParams lp)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView(android.view.View, RecyclerView.Recycler) scrapped}.

Parameters
child View: Child to reattach

index int: Intended child index for child

lp RecyclerView.LayoutParams: LayoutParams for child

attachView

public void attachView (View child, 
                int index)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView(android.view.View, RecyclerView.Recycler) scrapped}.

Parameters
child View: Child to reattach

index int: Intended child index for child

calculateItemDecorationsForChild

public void calculateItemDecorationsForChild (View child, 
                Rect outRect)

Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.

  • The Rect's left is set to the total width of left decorations.
  • The Rect's top is set to the total height of top decorations.
  • The Rect's right is set to the total width of right decorations.
  • The Rect's bottom is set to total height of bottom decorations.

Note that item decorations are automatically calculated when one of the LayoutManager's measure child methods is called. If you need to measure the child with custom specs via View.measure(int, int), you can use this method to get decorations.

Parameters
child View: The child view whose decorations should be calculated

outRect Rect: The Rect to hold result values

canScrollHorizontally

public boolean canScrollHorizontally ()

Query if horizontal scrolling is currently supported. The default implementation returns false.

Returns
boolean True if this LayoutManager can scroll the current contents horizontally

canScrollVertically

public boolean canScrollVertically ()

Query if vertical scrolling is currently supported. The default implementation returns false.

Returns
boolean True if this LayoutManager can scroll the current contents vertically

checkLayoutParams

public boolean checkLayoutParams (RecyclerView.LayoutParams lp)

Determines the validity of the supplied LayoutParams object.

This should check to make sure that the object is of the correct type and all values are within acceptable ranges. The default implementation returns true for non-null params.

Parameters
lp RecyclerView.LayoutParams: LayoutParams object to check

Returns
boolean true if this LayoutParams object is valid, false otherwise

chooseSize

public static int chooseSize (int spec, 
                int desired, 
                int min)

Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.

Parameters
spec int: The measureSpec

desired int: The preferred measurement

min int: The minimum value

Returns
int A size that fits to the given specs

collectAdjacentPrefetchPositions

public void collectAdjacentPrefetchPositions (int dx, 
                int dy, 
                RecyclerView.State state, 
                RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)

Gather all positions from the LayoutManager to be prefetched, given specified momentum.

If item prefetch is enabled, this method is called in between traversals to gather which positions the LayoutManager will soon need, given upcoming movement in subsequent traversals.

The LayoutManager should call RecyclerView.LayoutManager.LayoutPrefetchRegistry.addPosition(int, int) for each item to be prepared, and these positions will have their ViewHolders created and bound, if there is sufficient time available, in advance of being needed by a scroll or layout.

Parameters
dx int: X movement component.

dy int: Y movement component.

state RecyclerView.State: State of RecyclerView

layoutPrefetchRegistry RecyclerView.LayoutManager.LayoutPrefetchRegistry: PrefetchRegistry to add prefetch entries into.

collectInitialPrefetchPositions

public void collectInitialPrefetchPositions (int adapterItemCount, 
                RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)

Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView.

This method is only called when a RecyclerView is nested in another RecyclerView.

If item prefetch is enabled for this LayoutManager, as well in another containing LayoutManager, this method is called in between draw traversals to gather which positions this LayoutManager will first need, once it appears on the screen.

For example, if this LayoutManager represents a horizontally scrolling list within a vertically scrolling LayoutManager, this method would be called when the horizontal list is about to come onscreen.

The LayoutManager should call RecyclerView.LayoutManager.LayoutPrefetchRegistry.addPosition(int, int) for each item to be prepared, and these positions will have their ViewHolders created and bound, if there is sufficient time available, in advance of being needed by a scroll or layout.

Parameters
adapterItemCount int: number of items in the associated adapter.

layoutPrefetchRegistry RecyclerView.LayoutManager.LayoutPrefetchRegistry: PrefetchRegistry to add prefetch entries into.

computeHorizontalScrollExtent

public int computeHorizontalScrollExtent (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeHorizontalScrollExtent() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current state of RecyclerView

Returns
int The horizontal extent of the scrollbar's thumb

computeHorizontalScrollOffset

public int computeHorizontalScrollOffset (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeHorizontalScrollOffset() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current State of RecyclerView where you can find total item count

Returns
int The horizontal offset of the scrollbar's thumb

computeHorizontalScrollRange

public int computeHorizontalScrollRange (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeHorizontalScrollRange() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current State of RecyclerView where you can find total item count

Returns
int The total horizontal range represented by the vertical scrollbar

computeVerticalScrollExtent

public int computeVerticalScrollExtent (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeVerticalScrollExtent() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current state of RecyclerView

Returns
int The vertical extent of the scrollbar's thumb

computeVerticalScrollOffset

public int computeVerticalScrollOffset (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeVerticalScrollOffset() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current State of RecyclerView where you can find total item count

Returns
int The vertical offset of the scrollbar's thumb

computeVerticalScrollRange

public int computeVerticalScrollRange (RecyclerView.State state)

Override this method if you want to support scroll bars.

Read RecyclerView.computeVerticalScrollRange() for details.

Default implementation returns 0.

Parameters
state RecyclerView.State: Current State of RecyclerView where you can find total item count

Returns
int The total vertical range represented by the vertical scrollbar

detachAndScrapAttachedViews

public void detachAndScrapAttachedViews (RecyclerView.Recycler recycler)

Temporarily detach and scrap all currently attached child views. Views will be scrapped into the given Recycler. The Recycler may prefer to reuse scrap views before other views that were previously recycled.

Parameters
recycler RecyclerView.Recycler: Recycler to scrap views into

detachAndScrapView

public void detachAndScrapView (View child, 
                RecyclerView.Recycler recycler)

Detach a child view and add it to a Recycler's scrap heap.

Scrapping a view allows it to be rebound and reused to show updated or different data.

Parameters
child View: Child to detach and scrap

recycler RecyclerView.Recycler: Recycler to deposit the new scrap view into

detachAndScrapViewAt

public void detachAndScrapViewAt (int index, 
                RecyclerView.Recycler recycler)

Detach a child view and add it to a Recycler's scrap heap.

Scrapping a view allows it to be rebound and reused to show updated or different data.

Parameters
index int: Index of child to detach and scrap

recycler RecyclerView.Recycler: Recycler to deposit the new scrap view into

detachView

public void detachView (View child)

Temporarily detach a child view.

LayoutManagers may want to perform a lightweight detach operation to rearrange views currently attached to the RecyclerView. Generally LayoutManager implementations will want to use detachAndScrapView(android.view.View, RecyclerView.Recycler) so that the detached view may be rebound and reused.

If a LayoutManager uses this method to detach a view, it must reattach or fully remove the detached view before the LayoutManager entry point method called by RecyclerView returns.

Parameters
child View: Child to detach

detachViewAt

public void detachViewAt (int index)

Temporarily detach a child view.

LayoutManagers may want to perform a lightweight detach operation to rearrange views currently attached to the RecyclerView. Generally LayoutManager implementations will want to use detachAndScrapView(android.view.View, RecyclerView.Recycler) so that the detached view may be rebound and reused.

If a LayoutManager uses this method to detach a view, it must reattach or fully remove the detached view before the LayoutManager entry point method called by RecyclerView returns.

Parameters
index int: Index of the child to detach

endAnimation

public void endAnimation (View view)

Ends all animations on the view created by the RecyclerView.ItemAnimator.

Parameters
view View: The View for which the animations should be ended.

findContainingItemView

public View findContainingItemView (View view)

Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.

Note that this method may return null if the view is a child of the RecyclerView but not a child of the LayoutManager (e.g. running a disappear animation).

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

Returns
View The direct child of the LayoutManager which contains the given view or null if the provided view is not a descendant of this LayoutManager.

findViewByPosition

public View findViewByPosition (int position)

Finds the view which represents the given adapter position.

This method traverses each child since it has no information about child order. Override this method to improve performance if your LayoutManager keeps data about child views.

If a view is ignored via ignoreView(View), it is also ignored by this method.

Parameters
position int: Position of the item in adapter

Returns
View The child view that represents the given position or null if the position is not laid out

generateDefaultLayoutParams

public abstract RecyclerView.LayoutParams generateDefaultLayoutParams ()

Create a default LayoutParams object for a child of the RecyclerView.

LayoutManagers will often want to use a custom LayoutParams type to store extra information specific to the layout. Client code should subclass RecyclerView.LayoutParams for this purpose.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams(LayoutParams), generateLayoutParams(android.view.ViewGroup.LayoutParams) and generateLayoutParams(android.content.Context, android.util.AttributeSet).

Returns
RecyclerView.LayoutParams A new LayoutParams for a child view

generateLayoutParams

public RecyclerView.LayoutParams generateLayoutParams (Context c, 
                AttributeSet attrs)

Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams(LayoutParams), generateLayoutParams(android.view.ViewGroup.LayoutParams) and generateLayoutParams(android.content.Context, android.util.AttributeSet).

Parameters
c Context: Context for obtaining styled attributes

attrs AttributeSet: AttributeSet describing the supplied arguments

Returns
RecyclerView.LayoutParams a new LayoutParams object

generateLayoutParams

public RecyclerView.LayoutParams generateLayoutParams (ViewGroup.LayoutParams lp)

Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams(LayoutParams), generateLayoutParams(android.view.ViewGroup.LayoutParams) and generateLayoutParams(android.content.Context, android.util.AttributeSet).

Parameters
lp ViewGroup.LayoutParams: Source LayoutParams object to copy values from

Returns
RecyclerView.LayoutParams a new LayoutParams object

getBaseline

public int getBaseline ()

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

Returns
int The offset of the RecyclerView's text baseline from the its top boundary; -1 if there is no baseline.

getBottomDecorationHeight

public int getBottomDecorationHeight (View child)

Returns the total height of item decorations applied to child's bottom.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild(View, Rect) is called.

Parameters
child View: Child to query

Returns
int The total height of item decorations applied to the child's bottom.

getChildAt

public View getChildAt (int index)

Return the child view at the given index

Parameters
index int: Index of child to return

Returns
View Child view at index

getChildCount

public int getChildCount ()

Return the current number of child views attached to the parent RecyclerView. This does not include child views that were temporarily detached and/or scrapped.

Returns
int Number of attached children

getChildMeasureSpec

public static int getChildMeasureSpec (int parentSize, 
                int parentMode, 
                int padding, 
                int childDimension, 
                boolean canScroll)

Calculate a MeasureSpec value for measuring a child view in one dimension.

Parameters
parentSize int: Size of the parent view where the child will be placed

parentMode int: The measurement spec mode of the parent

padding int: Total space currently consumed by other elements of parent

childDimension int: Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT. Generally obtained from the child view's LayoutParams

canScroll boolean: true if the parent RecyclerView can scroll in this dimension

Returns
int a MeasureSpec value for the child view

getChildMeasureSpec

public static int getChildMeasureSpec (int parentSize, 
                int padding, 
                int childDimension, 
                boolean canScroll)

This method is deprecated.
use getChildMeasureSpec(int, int, int, int, boolean)

Calculate a MeasureSpec value for measuring a child view in one dimension.

Parameters
parentSize int: Size of the parent view where the child will be placed

padding int: Total space currently consumed by other elements of the parent

childDimension int: Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT. Generally obtained from the child view's LayoutParams

canScroll boolean: true if the parent RecyclerView can scroll in this dimension

Returns
int a MeasureSpec value for the child view

getClipToPadding

public boolean getClipToPadding ()

Check if the RecyclerView is configured to clip child views to its padding.

Returns
boolean true if this RecyclerView clips children to its padding, false otherwise

getColumnCountForAccessibility

public int getColumnCountForAccessibility (RecyclerView.Recycler recycler, 
                RecyclerView.State state)

Returns the number of columns for accessibility.

Default implementation returns the number of items in the adapter if LayoutManager supports horizontal scrolling or 1 if LayoutManager does not support horizontal scrolling.

Parameters
recycler RecyclerView.Recycler: The Recycler that can be used to convert view positions into adapter positions

state RecyclerView.State: The current state of RecyclerView

Returns
int The number of rows in LayoutManager for accessibility.

getDecoratedBottom

public int getDecoratedBottom (View child)

Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
child View: Child to query

Returns
int Child bottom edge with offsets applied

getDecoratedBoundsWithMargins

public void getDecoratedBoundsWithMargins (View view, 
                Rect outBounds)

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

Parameters
view View: The view element to check

outBounds Rect: A rect that will receive the bounds of the element including its decoration and margins.

getDecoratedLeft

public int getDecoratedLeft (View child)

Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
child View: Child to query

Returns
int Child left edge with offsets applied

getDecoratedMeasuredHeight

public int getDecoratedMeasuredHeight (View child)

Returns the measured height of the given child, plus the additional size of any insets applied by ItemDecorations.

Parameters
child View: Child view to query

Returns
int child's measured height plus ItemDecoration insets

getDecoratedMeasuredWidth

public int getDecoratedMeasuredWidth (View child)

Returns the measured width of the given child, plus the additional size of any insets applied by ItemDecorations.

Parameters
child View: Child view to query

Returns
int child's measured width plus ItemDecoration insets

getDecoratedRight

public int getDecoratedRight (View child)

Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
child View: Child to query

Returns
int Child right edge with offsets applied

getDecoratedTop

public int getDecoratedTop (View child)

Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
child View: Child to query

Returns
int Child top edge with offsets applied

getFocusedChild

public View getFocusedChild ()

Returns the item View which has or contains focus.

Returns
View A direct child of RecyclerView which has focus or contains the focused child.

getHeight

public int getHeight ()

Returns the height that is currently relevant to the LayoutManager.

This value is usually equal to the laid out height of the RecyclerView but may reflect the current View.MeasureSpec height if the RecyclerView.LayoutManager is using AutoMeasure and the RecyclerView is in the process of measuring. The LayoutManager must always use this method to retrieve the height relevant to it at any given time.

Returns
int Height in pixels

getHeightMode

public int getHeightMode ()

Return the height measurement spec mode that is currently relevant to the LayoutManager.

This value is set only if the LayoutManager opts into the AutoMeasure api via setAutoMeasureEnabled(boolean).

When RecyclerView is running a layout, this value is always set to View.MeasureSpec.EXACTLY even if it was measured with a different spec mode.

Returns
int Height measure spec mode

getItemCount

public int getItemCount ()

Returns the number of items in the adapter bound to the parent RecyclerView.

Note that this number is not necessarily equal to State#getItemCount(). In methods where RecyclerView.State is available, you should use State#getItemCount() instead. For more details, check the documentation for State#getItemCount().

Returns
int The number of items in the bound adapter

getItemViewType

public int getItemViewType (View view)

Returns the View type defined by the adapter.

Parameters
view View: The view to query

Returns
int The type of the view assigned by the adapter.

getLayoutDirection

public int getLayoutDirection ()

Returns the resolved layout direction for this RecyclerView.

Returns
int ViewCompat.LAYOUT_DIRECTION_RTL if the layout direction is RTL or returns ViewCompat.LAYOUT_DIRECTION_LTR if the layout direction is not RTL.

getLeftDecorationWidth

public int getLeftDecorationWidth (View child)

Returns the total width of item decorations applied to child's left.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild(View, Rect) is called.

Parameters
child View: Child to query

Returns
int The total width of item decorations applied to the child's left.

getMinimumHeight

public int getMinimumHeight ()

Returns
int The host RecyclerView's View.getMinimumHeight()

getMinimumWidth

public int getMinimumWidth ()

Returns
int The host RecyclerView's View.getMinimumWidth()

getPaddingBottom

public int getPaddingBottom ()

Return the bottom padding of the parent RecyclerView

Returns
int Padding in pixels

getPaddingEnd

public int getPaddingEnd ()

Return the end padding of the parent RecyclerView

Returns
int Padding in pixels

getPaddingLeft

public int getPaddingLeft ()

Return the left padding of the parent RecyclerView

Returns
int Padding in pixels

getPaddingRight

public int getPaddingRight ()

Return the right padding of the parent RecyclerView

Returns
int Padding in pixels

getPaddingStart

public int getPaddingStart ()

Return the start padding of the parent RecyclerView

Returns
int Padding in pixels

getPaddingTop

public int getPaddingTop ()

Return the top padding of the parent RecyclerView

Returns
int Padding in pixels

getPosition

public int getPosition (View view)

Returns the adapter position of the item represented by the given View. This does not contain any adapter changes that might have happened after the last layout.

Parameters
view View: The view to query

Returns
int The adapter position of the item which is rendered by this View.

getProperties

public static RecyclerView.LayoutManager.Properties getProperties (Context context, 
                AttributeSet attrs, 
                int defStyleAttr, 
                int defStyleRes)

Parse the xml attributes to get the most common properties used by layout managers. R.attr.orientation R.attr.spanCount R.attr.reverseLayout R.attr.stackFromEnd

Parameters
context Context

attrs AttributeSet

defStyleAttr int

defStyleRes int

Returns
RecyclerView.LayoutManager.Properties an object containing the properties as specified in the attrs.

getRightDecorationWidth

public int getRightDecorationWidth (View child)

Returns the total width of item decorations applied to child's right.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild(View, Rect) is called.

Parameters
child View: Child to query

Returns
int The total width of item decorations applied to the child's right.

getRowCountForAccessibility

public int getRowCountForAccessibility (RecyclerView.Recycler recycler, 
                RecyclerView.State state)

Returns the number of rows for accessibility.

Default implementation returns the number of items in the adapter if LayoutManager supports vertical scrolling or 1 if LayoutManager does not support vertical scrolling.

Parameters
recycler RecyclerView.Recycler: The Recycler that can be used to convert view positions into adapter positions

state RecyclerView.State: The current state of RecyclerView

Returns
int The number of rows in LayoutManager for accessibility.

getSelectionModeForAccessibility

public int getSelectionModeForAccessibility (RecyclerView.Recycler recycler, 
                RecyclerView.State state)

Returns the selection mode for accessibility. Should be AccessibilityNodeInfoCompat.CollectionInfoCompat.SELECTION_MODE_NONE, AccessibilityNodeInfoCompat.CollectionInfoCompat.SELECTION_MODE_SINGLE or AccessibilityNodeInfoCompat.CollectionInfoCompat.SELECTION_MODE_MULTIPLE.

Default implementation returns AccessibilityNodeInfoCompat.CollectionInfoCompat.SELECTION_MODE_NONE.

Parameters
recycler RecyclerView.Recycler: The Recycler that can be used to convert view positions into adapter positions

state RecyclerView.State: The current state of RecyclerView

Returns
int Selection mode for accessibility. Default implementation returns AccessibilityNodeInfoCompat.CollectionInfoCompat.SELECTION_MODE_NONE.

getTopDecorationHeight

public int getTopDecorationHeight (View child)

Returns the total height of item decorations applied to child's top.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild(View, Rect) is called.

Parameters
child View: Child to query

Returns
int The total height of item decorations applied to the child's top.

getTransformedBoundingBox

public void getTransformedBoundingBox (View child, 
                boolean includeDecorInsets, 
                Rect out)

Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.

If includeDecorInsets is true, they are applied first before applying the View's matrix so that the decor offsets also go through the same transformation.

Parameters
child View: The ItemView whose bounding box should be calculated.

includeDecorInsets boolean: True if the decor insets should be included in the bounding box

out Rect: The rectangle into which the output will be written.

getWidth

public int getWidth ()

Returns the width that is currently relevant to the LayoutManager.

This value is usually equal to the laid out width of the RecyclerView but may reflect the current View.MeasureSpec width if the RecyclerView.LayoutManager is using AutoMeasure and the RecyclerView is in the process of measuring. The LayoutManager must always use this method to retrieve the width relevant to it at any given time.

Returns
int Width in pixels

getWidthMode

public int getWidthMode ()

Return the width measurement spec mode that is currently relevant to the LayoutManager.

This value is set only if the LayoutManager opts into the AutoMeasure api via setAutoMeasureEnabled(boolean).

When RecyclerView is running a layout, this value is always set to View.MeasureSpec.EXACTLY even if it was measured with a different spec mode.

Returns
int Width measure spec mode

hasFocus

public boolean hasFocus ()

Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.

Returns
boolean true if the RecyclerView has or contains focus

See also:

ignoreView

public void ignoreView (View view)

Flags a view so that it will not be scrapped or recycled.

Scope of ignoring a child is strictly restricted to position tracking, scrapping and recyling. Methods like removeAndRecycleAllViews(Recycler) will ignore the child whereas removeAllViews() or offsetChildrenHorizontal(int) will not ignore the child.

Before this child can be recycled again, you have to call stopIgnoringView(View).

You can call this method only if your LayoutManger is in onLayout or onScroll callback.

Parameters
view View: View to ignore.

isAttachedToWindow

public boolean isAttachedToWindow ()

Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.

Returns
boolean True if this LayoutManager is controlling a RecyclerView and the RecyclerView is attached to window.

isAutoMeasureEnabled

public boolean isAutoMeasureEnabled ()

Returns whether the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or if it should be done by the LayoutManager's implementation of onMeasure(Recycler, State, int, int).

This method returns false by default (it actually returns the value passed to the deprecated setAutoMeasureEnabled(boolean)) and should be overridden to return true if a LayoutManager wants to be auto measured by the RecyclerView.

If this method is overridden to return true, onMeasure(Recycler, State, int, int) should not be overridden.

AutoMeasure is a RecyclerView mechanism that handles the measuring pass of layout in a simple and contract satisfying way, including the wrapping of children laid out by LayoutManager. Simply put, it handles wrapping children by calling onLayoutChildren(Recycler, State) during a call to RecyclerView.onMeasure(int, int), and then calculating desired dimensions based on children's dimensions and positions. It does this while supporting all existing animation capabilities of the RecyclerView.

More specifically:

  1. When RecyclerView.onMeasure(int, int) is called, if the provided measure specs both have a mode of View.MeasureSpec.EXACTLY, RecyclerView will set its measured dimensions accordingly and return, allowing layout to continue as normal (Actually, RecyclerView will call onMeasure(Recycler, State, int, int) for backwards compatibility reasons but it should not be overridden if AutoMeasure is being used).
  2. If one of the layout specs is not EXACT, the RecyclerView will start the layout process. It will first process all pending Adapter updates and then decide whether to run a predictive layout. If it decides to do so, it will first call onLayoutChildren(Recycler, State) with RecyclerView.State.isPreLayout() set to true. At this stage, getWidth() and getHeight() will still return the width and height of the RecyclerView as of the last layout calculation.

    After handling the predictive case, RecyclerView will call onLayoutChildren(Recycler, State) with RecyclerView.State.isMeasuring() set to true and RecyclerView.State.isPreLayout() set to false. The LayoutManager can access the measurement specs via getHeight(), getHeightMode(), getWidth() and getWidthMode().

  3. After the layout calculation, RecyclerView sets the measured width & height by calculating the bounding box for the children (+ RecyclerView's padding). The LayoutManagers can override setMeasuredDimension(Rect, int, int) to choose different values. For instance, GridLayoutManager overrides this value to handle the case where if it is vertical and has 3 columns but only 2 items, it should still measure its width to fit 3 items, not 2.
  4. Any following calls to RecyclerView.onMeasure(int, int) will run onLayoutChildren(Recycler, State) with RecyclerView.State.isMeasuring() set to true and RecyclerView.State.isPreLayout() set to false. RecyclerView will take care of which views are actually added / removed / moved / changed for animations so that the LayoutManager should not worry about them and handle each onLayoutChildren(Recycler, State) call as if it is the last one.
  5. When measure is complete and RecyclerView's RecyclerView.onLayout(boolean, int, int, int, int) method is called, RecyclerView checks whether it already did layout calculations during the measure pass and if so, it re-uses that information. It may still decide to call onLayoutChildren(Recycler, State) if the last measure spec was different from the final dimensions or adapter contents have changed between the measure call and the layout call.
  6. Finally, animations are calculated and run as usual.

Returns
boolean True if the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or False if it should be done by the LayoutManager's implementation of onMeasure(Recycler, State, int, int).

isFocused

public boolean isFocused ()

Returns true if the RecyclerView this LayoutManager is bound to has focus.

Returns
boolean True if the RecyclerView has focus, false otherwise.

See also:

isItemPrefetchEnabled

public final boolean isItemPrefetchEnabled ()

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

Returns
boolean true if item prefetch is enabled, false otherwise

isLayoutHierarchical

public boolean isLayoutHierarchical (RecyclerView.Recycler recycler, 
                RecyclerView.State state)

Returns whether layout is hierarchical or not to be used for accessibility.

Default implementation returns false.

Parameters
recycler RecyclerView.Recycler: The Recycler that can be used to convert view positions into adapter positions

state RecyclerView.State: The current state of RecyclerView

Returns
boolean True if layout is hierarchical.

isMeasurementCacheEnabled

public boolean isMeasurementCacheEnabled ()

In addition to the View Framework's measurement cache, RecyclerView uses its own additional measurement cache for its children to avoid re-measuring them when not necessary. It is on by default but it can be turned off via setMeasurementCacheEnabled(boolean).

Returns
boolean True if measurement cache is enabled, false otherwise.

isSmoothScrolling

public boolean isSmoothScrolling ()

Returns
boolean true if RecyclerView is currently in the state of smooth scrolling.

isViewPartiallyVisible

public boolean isViewPartiallyVisible (View child, 
                boolean completelyVisible, 
                boolean acceptEndPointInclusion)

Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters. A view is partially visible if it has non-zero overlap with RV's padded bounded area. If acceptEndPointInclusion flag is set to true, it's also considered partially visible if it's located outside RV's bounds and it's hitting either RV's start or end bounds.

Parameters
child View: The child view to be examined.

completelyVisible boolean: If true, the method returns true if and only if the child is completely visible. If false, the method returns true if and only if the child is only partially visible (that is it will return false if the child is either completely visible or out of RV's bounds).

acceptEndPointInclusion boolean: If the view's endpoint intersection with RV's start of end bounds is enough to consider it partially visible, false otherwise.

Returns
boolean True if the given child is partially or fully visible, false otherwise.

layoutDecorated

public void layoutDecorated (View child, 
                int left, 
                int top, 
                int right, 
                int bottom)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations.

LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:

Parameters
child View: Child to lay out

left int: Left edge, with item decoration insets included

top int: Top edge, with item decoration insets included

right int: Right edge, with item decoration insets included

bottom int: Bottom edge, with item decoration insets included

layoutDecoratedWithMargins

public void layoutDecoratedWithMargins (View child, 
                int left, 
                int top, 
                int right, 
                int bottom)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations and margins.

LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:

Parameters
child View: Child to lay out

left int: Left edge, with item decoration insets and left margin included

top int: Top edge, with item decoration insets and top margin included

right int: Right edge, with item decoration insets and right margin included

bottom int: Bottom edge, with item decoration insets and bottom margin included

measureChild

public void measureChild (View child, 
                int widthUsed, 
                int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.

If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.

Parameters
child View: Child view to measure

widthUsed int: Width in pixels currently consumed by other views, if relevant

heightUsed int: Height in pixels currently consumed by other views, if relevant

measureChildWithMargins

public void measureChildWithMargins (View child, 
                int widthUsed, 
                int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account.

If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.

Parameters
child View: Child view to measure

widthUsed int: Width in pixels currently consumed by other views, if relevant

heightUsed int: Height in pixels currently consumed by other views, if relevant

moveView

public void moveView (int fromIndex, 
                int toIndex)

Moves a View from one position to another.

Parameters
fromIndex int: The View's initial index

toIndex int: The View's target index

offsetChildrenHorizontal

public void offsetChildrenHorizontal (int dx)

Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.

Parameters
dx int: Pixels to offset by

offsetChildrenVertical

public void offsetChildrenVertical (int dy)

Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.

Parameters
dy int: Pixels to offset by

onAdapterChanged

public void onAdapterChanged (Adapter oldAdapter, 
                Adapter newAdapter)

Called if the RecyclerView this LayoutManager is bound to has a different adapter set via RecyclerView.setAdapter(Adapter) or RecyclerView.swapAdapter(Adapter, boolean). The LayoutManager may use this opportunity to clear caches and configure state such that it can relayout appropriately with the new data and potentially new view types.

The default implementation removes all currently attached views.

Parameters
oldAdapter Adapter: The previous adapter instance. Will be null if there was previously no adapter.

newAdapter Adapter: The new adapter instance. Might be null if RecyclerView.setAdapter(RecyclerView.Adapter) is called with null.

onAddFocusables

public boolean onAddFocusables (RecyclerView recyclerView, 
                ArrayList<View> views, 
                int direction, 
                int focusableMode)

Called to populate focusable views within the RecyclerView.

The LayoutManager implementation should return true if the default behavior of View.addFocusables(java.util.ArrayList, int) should be suppressed.

The default implementation returns false to trigger RecyclerView to fall back to the default ViewGroup behavior.

Parameters
recyclerView RecyclerView: The RecyclerView hosting this LayoutManager

views ArrayList: List of output views. This method should add valid focusable views to this list.

direction int: One of View.FOCUS_UP, View.FOCUS_DOWN, View.FOCUS_LEFT, View.FOCUS_RIGHT, View.FOCUS_BACKWARD, View.FOCUS_FORWARD

focusableMode int: The type of focusables to be added.

Returns
boolean true to suppress the default behavior, false to add default focusables after this method returns.

onAttachedToWindow

public void onAttachedToWindow (RecyclerView view)

Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.

If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not call onLayoutChildren(Recycler, State) if nothing has changed and a layout was not requested on the RecyclerView while it was detached.

Subclass implementations should always call through to the superclass implementation.

Parameters
view RecyclerView: The RecyclerView this LayoutManager is bound to

onDetachedFromWindow

public void onDetachedFromWindow (RecyclerView view)

This method is deprecated.
override onDetachedFromWindow(RecyclerView, Recycler)

Parameters
view RecyclerView

onDetachedFromWindow

public void onDetachedFromWindow (RecyclerView view, 
                RecyclerView.Recycler recycler)

Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.

LayoutManager should clear all of its View references as another LayoutManager might be assigned to the RecyclerView.

If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not call onLayoutChildren(Recycler, State) if nothing has changed and a layout was not requested on the RecyclerView while it was detached.

If your LayoutManager has View references that it cleans in on-detach, it should also call RecyclerView.requestLayout() to ensure that it is re-laid out when RecyclerView is re-attached.

Subclass implementations should always call through to the superclass implementation.

Parameters
view RecyclerView: The RecyclerView this LayoutManager is bound to

recycler RecyclerView.Recycler: The recycler to use if you prefer to recycle your children instead of keeping them around.

onFocusSearchFailed

public View onFocusSearchFailed (View focused, 
                int direction, 
                RecyclerView.Recycler recycler, 
                RecyclerView.State state)

Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.

This is the LayoutManager's opportunity to populate views in the given direction to fulfill the request if it can. The LayoutManager should attach and return the view to be focused, if a focusable view in the given direction is found. Otherwise, if all the existing (or the newly populated views) are unfocusable, it returns the next unfocusable view to become visible on the screen. This unfocusable view is typically the first view that's either partially or fully out of RV's padded bounded area in the given direction. The default implementation returns null.

Parameters
focused View: The currently focused view

direction int: One of View.FOCUS_UP, View.FOCUS_DOWN, View.FOCUS_LEFT, View.FOCUS_RIGHT, View.FOCUS_BACKWARD, View.FOCUS_FORWARD or 0 for not applicable

recycler RecyclerView.Recycler: The recycler to use for obtaining views for currently offscreen items

state RecyclerView.State: Transient state of RecyclerView

Returns
View The chosen view to be focused if a focusable view is found, otherwise an unfocusable view to become visible onto the screen, else null.

onInitializeAccessibilityEvent

public void onInitializeAccessibilityEvent (AccessibilityEvent event)

Parameters
event AccessibilityEvent

onInitializeAccessibilityEvent

public void onInitializeAccessibilityEvent (RecyclerView.Recycler recycler, 
                RecyclerView.State state, 
                AccessibilityEvent event)

Called by the accessibility delegate to initialize an accessibility event.

Default implementation adds item count and scroll information to the event.

Parameters
recycler RecyclerView.Recycler: The Recycler that can be used to convert view positions into adapter positions

state RecyclerView.State: The current state of RecyclerView

event AccessibilityEvent: The event instance to initialize

onInitializeAccessibilityNodeInfo

public void onInitializeAccessibilityNodeInfo (RecyclerView.Recycler recycler, 
                RecyclerView.State state, 
                AccessibilityNodeInfoCompat info)

Called by the AccessibilityDelegate when the information about the current layout should be populated.

Default implementation adds a