recyclerview/androidx.recyclerview.widget/RecyclerView/LayoutManager

LayoutManager

abstract class LayoutManager(source)

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. In case a LayoutManager specifies both constructors, the non-default constructor will take precedence.

Inheritors

Constructors

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constructor()

Types

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interface LayoutPrefetchRegistry
Interface for LayoutManagers to request items to be prefetched, based on position, with specified distance from viewport, which indicates priority.
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open class Properties
Some general properties that a LayoutManager may want to use.

Functions

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open fun addDisappearingView(child: View)
open fun addDisappearingView(child: View, index: Int)
To be called only during onLayoutChildren 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.
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open fun addView(child: View)
open fun addView(child: View, index: Int)
Add a view to the currently attached RecyclerView if needed.
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open fun assertInLayoutOrScroll(message: String)
Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is not.
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open fun assertNotInLayoutOrScroll(message: String)
Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is.
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open fun attachView(@NonNull child: View)
open fun attachView(@NonNull child: View, index: Int)
open fun attachView(@NonNull child: View, index: Int, lp: RecyclerView.LayoutParams)
Reattach a previously detached view.
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open fun calculateItemDecorationsForChild(@NonNull child: View, @NonNull outRect: Rect)
Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.
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open fun canScrollHorizontally(): Boolean
Query if horizontal scrolling is currently supported.
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open fun canScrollVertically(): Boolean
Query if vertical scrolling is currently supported.
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open fun checkLayoutParams(lp: RecyclerView.LayoutParams): Boolean
Determines the validity of the supplied LayoutParams object.
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open fun chooseSize(spec: Int, desired: Int, min: Int): Int
Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.
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open fun collectAdjacentPrefetchPositions(dx: Int, dy: Int, state: RecyclerView.State, layoutPrefetchRegistry: RecyclerView.LayoutManager.LayoutPrefetchRegistry)
Gather all positions from the LayoutManager to be prefetched, given specified momentum.
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open fun collectInitialPrefetchPositions(adapterItemCount: Int, layoutPrefetchRegistry: RecyclerView.LayoutManager.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.
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open fun computeHorizontalScrollExtent(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun computeHorizontalScrollOffset(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun computeHorizontalScrollRange(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun computeVerticalScrollExtent(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun computeVerticalScrollOffset(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun computeVerticalScrollRange(@NonNull state: RecyclerView.State): Int
Override this method if you want to support scroll bars.
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open fun detachAndScrapAttachedViews(@NonNull recycler: RecyclerView.Recycler)
Temporarily detach and scrap all currently attached child views.
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open fun detachAndScrapView(@NonNull child: View, @NonNull recycler: RecyclerView.Recycler)
Detach a child view and add it to a Recycler's scrap heap.
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open fun detachAndScrapViewAt(index: Int, @NonNull recycler: RecyclerView.Recycler)
Detach a child view and add it to a Recycler's scrap heap.
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open fun detachView(@NonNull child: View)
Temporarily detach a child view.
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open fun detachViewAt(index: Int)
Temporarily detach a child view.
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open fun endAnimation(view: View)
Ends all animations on the view created by the ItemAnimator.
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@Nullable
open fun findContainingItemView(@NonNull view: View): View
Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.
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@Nullable
open fun findViewByPosition(position: Int): View
Finds the view which represents the given adapter position.
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abstract fun generateDefaultLayoutParams(): RecyclerView.LayoutParams
Create a default LayoutParams object for a child of the RecyclerView.
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open fun generateLayoutParams(lp: ViewGroup.LayoutParams): RecyclerView.LayoutParams
Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.
open fun generateLayoutParams(c: Context, attrs: AttributeSet): RecyclerView.LayoutParams
Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.
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open fun getBaseline(): Int
Returns offset of the RecyclerView's text baseline from the its top boundary.
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open fun getBottomDecorationHeight(@NonNull child: View): Int
Returns the total height of item decorations applied to child's bottom.
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@Nullable
open fun getChildAt(index: Int): View
Return the child view at the given index
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open fun getChildCount(): Int
Return the current number of child views attached to the parent RecyclerView.
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open fun getChildMeasureSpec(parentSize: Int, padding: Int, childDimension: Int, canScroll: Boolean): Int
open fun getChildMeasureSpec(parentSize: Int, parentMode: Int, padding: Int, childDimension: Int, canScroll: Boolean): Int
Calculate a MeasureSpec value for measuring a child view in one dimension.
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open fun getClipToPadding(): Boolean
Check if the RecyclerView is configured to clip child views to its padding.
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open fun getColumnCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
Returns the number of columns for accessibility.
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open fun getDecoratedBottom(@NonNull child: View): Int
Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations.
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open fun getDecoratedBoundsWithMargins(@NonNull view: View, @NonNull outBounds: Rect)
Returns the bounds of the view including its decoration and margins.
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open fun getDecoratedLeft(@NonNull child: View): Int
Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations.
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open fun getDecoratedMeasuredHeight(@NonNull child: View): Int
Returns the measured height of the given child, plus the additional size of any insets applied by ItemDecorations.
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open fun getDecoratedMeasuredWidth(@NonNull child: View): Int
Returns the measured width of the given child, plus the additional size of any insets applied by ItemDecorations.
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open fun getDecoratedRight(@NonNull child: View): Int
Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations.
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open fun getDecoratedTop(@NonNull child: View): Int
Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations.
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@Nullable
open fun getFocusedChild(): View
Returns the item View which has or contains focus.
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@Px
open fun getHeight(): Int
Returns the height that is currently relevant to the LayoutManager.
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open fun getHeightMode(): Int
Return the height measurement spec mode that is currently relevant to the LayoutManager.
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open fun getItemCount(): Int
Returns the number of items in the adapter bound to the parent RecyclerView.
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open fun getItemViewType(@NonNull view: View): Int
Returns the View type defined by the adapter.
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open fun getLayoutDirection(): Int
Returns the resolved layout direction for this RecyclerView.
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open fun getLeftDecorationWidth(@NonNull child: View): Int
Returns the total width of item decorations applied to child's left.
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@Px
open fun getMinimumHeight(): Int
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@Px
open fun getMinimumWidth(): Int
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@Px
open fun getPaddingBottom(): Int
Return the bottom padding of the parent RecyclerView
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@Px
open fun getPaddingEnd(): Int
Return the end padding of the parent RecyclerView
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@Px
open fun getPaddingLeft(): Int
Return the left padding of the parent RecyclerView
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@Px
open fun getPaddingRight(): Int
Return the right padding of the parent RecyclerView
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@Px
open fun getPaddingStart(): Int
Return the start padding of the parent RecyclerView
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@Px
open fun getPaddingTop(): Int
Return the top padding of the parent RecyclerView
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open fun getPosition(@NonNull view: View): Int
Returns the adapter position of the item represented by the given View.
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open fun getProperties(@NonNull context: Context, @Nullable attrs: AttributeSet, defStyleAttr: Int, defStyleRes: Int): RecyclerView.LayoutManager.Properties
Parse the xml attributes to get the most common properties used by layout managers.
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open fun getRightDecorationWidth(@NonNull child: View): Int
Returns the total width of item decorations applied to child's right.
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open fun getRowCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
Returns the number of rows for accessibility.
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open fun getSelectionModeForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
Returns the selection mode for accessibility.
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open fun getTopDecorationHeight(@NonNull child: View): Int
Returns the total height of item decorations applied to child's top.
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open fun getTransformedBoundingBox(@NonNull child: View, includeDecorInsets: Boolean, @NonNull out: Rect)
Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.
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@Px
open fun getWidth(): Int
Returns the width that is currently relevant to the LayoutManager.
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open fun getWidthMode(): Int
Return the width measurement spec mode that is currently relevant to the LayoutManager.
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open fun hasFocus(): Boolean
Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.
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open fun ignoreView(@NonNull view: View)
Flags a view so that it will not be scrapped or recycled.
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open fun isAttachedToWindow(): Boolean
Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.
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open fun isAutoMeasureEnabled(): Boolean
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.
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open fun isFocused(): Boolean
Returns true if the RecyclerView this LayoutManager is bound to has focus.
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fun isItemPrefetchEnabled(): Boolean
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.
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open fun isLayoutHierarchical(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Boolean
Returns whether layout is hierarchical or not to be used for accessibility.
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open fun isLayoutReversed(): Boolean
Query if the layout is in reverse order.
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open fun isMeasurementCacheEnabled(): Boolean
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.
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open fun isViewPartiallyVisible(@NonNull child: View, completelyVisible: Boolean, acceptEndPointInclusion: Boolean): Boolean
Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters.
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open fun layoutDecorated(@NonNull child: View, left: Int, top: Int, right: Int, bottom: Int)
Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations.
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open fun layoutDecoratedWithMargins(@NonNull child: View, left: Int, top: Int, right: Int, bottom: Int)
Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations and margins.
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open fun measureChild(@NonNull child: View, widthUsed: Int, heightUsed: Int)
Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.
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open fun measureChildWithMargins(@NonNull child: View, widthUsed: Int, heightUsed: Int)
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.
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open fun moveView(fromIndex: Int, toIndex: Int)
Moves a View from one position to another.
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open fun offsetChildrenHorizontal(@Px dx: Int)
Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.
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open fun offsetChildrenVertical(@Px dy: Int)
Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.
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open fun onAdapterChanged(@Nullable oldAdapter: RecyclerView.Adapter, @Nullable newAdapter: RecyclerView.Adapter)
Called if the RecyclerView this LayoutManager is bound to has a different adapter set via setAdapter or swapAdapter.
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open fun onAddFocusables(@NonNull recyclerView: RecyclerView, @NonNull views: ArrayList<View>, direction: Int, focusableMode: Int): Boolean
Called to populate focusable views within the RecyclerView.
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@CallSuper
open fun onAttachedToWindow(view: RecyclerView)
Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.
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open fun onDetachedFromWindow(view: RecyclerView)

@CallSuper
open fun onDetachedFromWindow(view: RecyclerView, recycler: RecyclerView.Recycler)
Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.
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@Nullable
open fun onFocusSearchFailed(@NonNull focused: View, direction: Int, @NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): View
Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.
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open fun onInitializeAccessibilityEvent(@NonNull event: AccessibilityEvent)

open fun onInitializeAccessibilityEvent(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull event: AccessibilityEvent)
Called by the accessibility delegate to initialize an accessibility event.
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open fun onInitializeAccessibilityNodeInfo(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull info: AccessibilityNodeInfoCompat)
Called by the AccessibilityDelegate when the information about the current layout should be populated.
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open fun onInitializeAccessibilityNodeInfoForItem(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull host: View, @NonNull info: AccessibilityNodeInfoCompat)
Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated.
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@Nullable
open fun onInterceptFocusSearch(@NonNull focused: View, direction: Int): View
This method gives a LayoutManager an opportunity to intercept the initial focus search before the default behavior of FocusFinder is used.
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open fun onItemsAdded(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int)
Called when items have been added to the adapter.
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open fun onItemsChanged(@NonNull recyclerView: RecyclerView)
Called in response to a call to notifyDataSetChanged or swapAdapter ()} and signals that the the entire data set has changed.
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open fun onItemsMoved(@NonNull recyclerView: RecyclerView, from: Int, to: Int, itemCount: Int)
Called when an item is moved withing the adapter.
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open fun onItemsRemoved(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int)
Called when items have been removed from the adapter.
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open fun onItemsUpdated(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int)
Called when items have been changed in the adapter.
open fun onItemsUpdated(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int, @Nullable payload: Any)
Called when items have been changed in the adapter and with optional payload.
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open fun onLayoutChildren(recycler: RecyclerView.Recycler, state: RecyclerView.State)
Lay out all relevant child views from the given adapter.
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open fun onLayoutCompleted(state: RecyclerView.State)
Called after a full layout calculation is finished.
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open fun onMeasure(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, widthSpec: Int, heightSpec: Int)
Measure the attached RecyclerView.
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open fun onRequestChildFocus(@NonNull parent: RecyclerView, @NonNull child: View, @Nullable focused: View): Boolean

open fun onRequestChildFocus(@NonNull parent: RecyclerView, @NonNull state: RecyclerView.State, @NonNull child: View, @Nullable focused: View): Boolean
Called when a descendant view of the RecyclerView requests focus.
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open fun onRestoreInstanceState(state: Parcelable)
Called when the RecyclerView is ready to restore the state based on a previous RecyclerView.
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@Nullable
open fun onSaveInstanceState(): Parcelable
Called when the LayoutManager should save its state.
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open fun onScrollStateChanged(state: Int)
RecyclerView calls this method to notify LayoutManager that scroll state has changed.
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open fun performAccessibilityAction(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, action: Int, @Nullable args: Bundle): Boolean
Called by AccessibilityDelegate when an action is requested from the RecyclerView.
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open fun performAccessibilityActionForItem(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull view: View, action: Int, @Nullable args: Bundle): Boolean
Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager.
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open fun postOnAnimation(action: Runnable)
Causes the Runnable to execute on the next animation time step.
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open fun removeAllViews()
Remove all views from the currently attached RecyclerView.
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open fun removeAndRecycleAllViews(@NonNull recycler: RecyclerView.Recycler)
Removes all views and recycles them using the given recycler.
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open fun removeAndRecycleView(@NonNull child: View, @NonNull recycler: RecyclerView.Recycler)
Remove a child view and recycle it using the given Recycler.
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open fun removeAndRecycleViewAt(index: Int, @NonNull recycler: RecyclerView.Recycler)
Remove a child view and recycle it using the given Recycler.
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open fun removeCallbacks(action: Runnable): Boolean
Removes the specified Runnable from the message queue.
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open fun removeDetachedView(@NonNull child: View)
Finish removing a view that was previously temporarily detached.
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open fun removeView(child: View)
Remove a view from the currently attached RecyclerView if needed.
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open fun removeViewAt(index: Int)
Remove a view from the currently attached RecyclerView if needed.
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open fun requestChildRectangleOnScreen(@NonNull parent: RecyclerView, @NonNull child: View, @NonNull rect: Rect, immediate: Boolean): Boolean
Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen.
open fun requestChildRectangleOnScreen(@NonNull parent: RecyclerView, @NonNull child: View, @NonNull rect: Rect, immediate: Boolean, focusedChildVisible: Boolean): Boolean
Requests that the given child of the RecyclerView be positioned onto the screen.
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open fun requestLayout()
Calls RecyclerView#requestLayout on the underlying RecyclerView
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open fun 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.
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open fun scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler, state: RecyclerView.State): Int
Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.
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open fun scrollToPosition(position: Int)
Scroll to the specified adapter position.
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open fun scrollVerticallyBy(dy: Int, recycler: RecyclerView.Recycler, state: RecyclerView.State): Int
Scroll vertically by dy pixels in screen coordinates and return the distance traveled.
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open fun setAutoMeasureEnabled(enabled: Boolean)
Defines 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.
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fun setItemPrefetchEnabled(enabled: Boolean)
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.
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open fun setMeasuredDimension(widthSize: Int, heightSize: Int)
Set the measured dimensions of the host RecyclerView.
open fun setMeasuredDimension(childrenBounds: Rect, wSpec: Int, hSpec: Int)
Sets the measured dimensions from the given bounding box of the children and the measurement specs that were passed into onMeasure.
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open fun setMeasurementCacheEnabled(measurementCacheEnabled: Boolean)
Sets whether RecyclerView should use its own measurement cache for the children.
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open fun smoothScrollToPosition(recyclerView: RecyclerView, state: RecyclerView.State, position: Int)
Smooth scroll to the specified adapter position.
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open fun startSmoothScroll(smoothScroller: RecyclerView.SmoothScroller)
Starts a smooth scroll using the provided SmoothScroller.
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open fun stopIgnoringView(@NonNull view: View)
View can be scrapped and recycled again.
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open fun supportsPredictiveItemAnimations(): Boolean
Returns whether this LayoutManager supports "predictive item animations".