LayoutManager
abstract class LayoutManager
kotlin.Any | |
↳ | 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.
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 |
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abstract |
Interface for LayoutManagers to request items to be prefetched, based on position, with specified distance from viewport, which indicates priority. |
open |
Some general properties that a LayoutManager may want to use. |
Public constructors |
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<init>() A |
Public methods |
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open Unit |
addDisappearingView(child: View!) To be called only during |
open Unit |
addDisappearingView(child: View!, index: Int) To be called only during |
open Unit |
Add a view to the currently attached RecyclerView if needed. |
open Unit |
Add a view to the currently attached RecyclerView if needed. |
open Unit |
assertInLayoutOrScroll(message: String!) Checks if RecyclerView is in the middle of a layout or scroll and throws an |
open Unit |
assertNotInLayoutOrScroll(message: String!) Checks if RecyclerView is in the middle of a layout or scroll and throws an |
open Unit |
attachView(@NonNull child: View, index: Int, lp: RecyclerView.LayoutParams!) Reattach a previously |
open Unit |
attachView(@NonNull child: View, index: Int) Reattach a previously |
open Unit |
attachView(@NonNull child: View) Reattach a previously |
open Unit |
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. |
open Boolean |
Query if horizontal scrolling is currently supported. |
open Boolean |
Query if vertical scrolling is currently supported. |
open Boolean |
Determines the validity of the supplied LayoutParams object. |
open static Int |
chooseSize(spec: Int, desired: Int, min: Int) Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec. |
open Unit |
collectAdjacentPrefetchPositions(dx: Int, dy: Int, state: RecyclerView.State!, layoutPrefetchRegistry: RecyclerView.LayoutManager.LayoutPrefetchRegistry!) Gather all positions from the LayoutManager to be prefetched, given specified momentum. |
open Unit |
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. |
open Int |
computeHorizontalScrollExtent(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Int |
computeHorizontalScrollOffset(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Int |
computeHorizontalScrollRange(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Int |
computeVerticalScrollExtent(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Int |
computeVerticalScrollOffset(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Int |
computeVerticalScrollRange(@NonNull state: RecyclerView.State) Override this method if you want to support scroll bars. |
open Unit |
detachAndScrapAttachedViews(@NonNull recycler: RecyclerView.Recycler) Temporarily detach and scrap all currently attached child views. |
open Unit |
detachAndScrapView(@NonNull child: View, @NonNull recycler: RecyclerView.Recycler) Detach a child view and add it to a |
open Unit |
detachAndScrapViewAt(index: Int, @NonNull recycler: RecyclerView.Recycler) Detach a child view and add it to a |
open Unit |
detachView(@NonNull child: View) Temporarily detach a child view. |
open Unit |
detachViewAt(index: Int) Temporarily detach a child view. |
open Unit |
endAnimation(view: View!) Ends all animations on the view created by the |
open View? |
findContainingItemView(@NonNull view: View) Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager. |
open View? |
findViewByPosition(position: Int) Finds the view which represents the given adapter position. |
abstract RecyclerView.LayoutParams! |
Create a default |
open RecyclerView.LayoutParams! |
Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible. |
open RecyclerView.LayoutParams! |
generateLayoutParams(c: Context!, attrs: AttributeSet!) Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource. |
open Int |
Returns offset of the RecyclerView's text baseline from the its top boundary. |
open Int |
getBottomDecorationHeight(@NonNull child: View) Returns the total height of item decorations applied to child's bottom. |
open View? |
getChildAt(index: Int) Return the child view at the given index |
open Int |
Return the current number of child views attached to the parent RecyclerView. |
open static Int |
getChildMeasureSpec(parentSize: Int, padding: Int, childDimension: Int, canScroll: Boolean) Calculate a MeasureSpec value for measuring a child view in one dimension. |
open static Int |
getChildMeasureSpec(parentSize: Int, parentMode: Int, padding: Int, childDimension: Int, canScroll: Boolean) Calculate a MeasureSpec value for measuring a child view in one dimension. |
open Boolean |
Check if the RecyclerView is configured to clip child views to its padding. |
open Int |
getColumnCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State) Returns the number of columns for accessibility. |
open Int |
getDecoratedBottom(@NonNull child: View) Returns the bottom edge of the given child view within its parent, offset by any applied |
open Unit |
getDecoratedBoundsWithMargins(@NonNull view: View, @NonNull outBounds: Rect) Returns the bounds of the view including its decoration and margins. |
open Int |
getDecoratedLeft(@NonNull child: View) Returns the left edge of the given child view within its parent, offset by any applied |
open Int |
getDecoratedMeasuredHeight(@NonNull child: View) Returns the measured height of the given child, plus the additional size of any insets applied by |
open Int |
getDecoratedMeasuredWidth(@NonNull child: View) Returns the measured width of the given child, plus the additional size of any insets applied by |
open Int |
getDecoratedRight(@NonNull child: View) Returns the right edge of the given child view within its parent, offset by any applied |
open Int |
getDecoratedTop(@NonNull child: View) Returns the top edge of the given child view within its parent, offset by any applied |
open View? |
Returns the item View which has or contains focus. |
open Int |
Returns the height that is currently relevant to the LayoutManager. |
open Int |
Return the height measurement spec mode that is currently relevant to the LayoutManager. |
open Int |
Returns the number of items in the adapter bound to the parent RecyclerView. |
open Int |
getItemViewType(@NonNull view: View) Returns the View type defined by the adapter. |
open Int |
Returns the resolved layout direction for this RecyclerView. |
open Int |
getLeftDecorationWidth(@NonNull child: View) Returns the total width of item decorations applied to child's left. |
open Int | |
open Int | |
open Int |
Return the bottom padding of the parent RecyclerView |
open Int |
Return the end padding of the parent RecyclerView |
open Int |
Return the left padding of the parent RecyclerView |
open Int |
Return the right padding of the parent RecyclerView |
open Int |
Return the start padding of the parent RecyclerView |
open Int |
Return the top padding of the parent RecyclerView |
open Int |
getPosition(@NonNull view: View) Returns the adapter position of the item represented by the given View. |
open static RecyclerView.LayoutManager.Properties! |
getProperties(@NonNull context: Context, @Nullable attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) Parse the xml attributes to get the most common properties used by layout managers. |
open Int |
getRightDecorationWidth(@NonNull child: View) Returns the total width of item decorations applied to child's right. |
open Int |
getRowCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State) Returns the number of rows for accessibility. |
open Int |
getSelectionModeForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State) Returns the selection mode for accessibility. |
open Int |
getTopDecorationHeight(@NonNull child: View) Returns the total height of item decorations applied to child's top. |
open Unit |
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. |
open Int |
getWidth() Returns the width that is currently relevant to the LayoutManager. |
open Int |
Return the width measurement spec mode that is currently relevant to the LayoutManager. |
open Boolean |
hasFocus() Returns true if the RecyclerView this LayoutManager is bound to has or contains focus. |
open Unit |
ignoreView(@NonNull view: View) Flags a view so that it will not be scrapped or recycled. |
open Boolean |
Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window. |
open Boolean |
Returns whether the measuring pass of layout should use the AutoMeasure mechanism of |
open Boolean |
Returns true if the RecyclerView this LayoutManager is bound to has focus. |
Boolean |
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames. |
open Boolean |
isLayoutHierarchical(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State) Returns whether layout is hierarchical or not to be used for accessibility. |
open 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. |
open Boolean | |
open Boolean |
isViewPartiallyVisible(@NonNull child: View, completelyVisible: Boolean, acceptEndPointInclusion: Boolean) Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters. |
open Unit |
Lay out the given child view within the RecyclerView using coordinates that include any current |
open Unit |
Lay out the given child view within the RecyclerView using coordinates that include any current |
open Unit |
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. |
open Unit |
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. |
open Unit |
Moves a View from one position to another. |
open Unit |
offsetChildrenHorizontal(@Px dx: Int) Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis. |
open Unit |
offsetChildrenVertical(@Px dy: Int) Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis. |
open Unit |
onAdapterChanged(@Nullable oldAdapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?, @Nullable newAdapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?) Called if the RecyclerView this LayoutManager is bound to has a different adapter set via |
open Boolean |
onAddFocusables(@NonNull recyclerView: RecyclerView, @NonNull views: ArrayList<View!>, direction: Int, focusableMode: Int) Called to populate focusable views within the RecyclerView. |
open Unit |
onAttachedToWindow(view: RecyclerView!) Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window. |
open Unit |
onDetachedFromWindow(view: RecyclerView!) |
open Unit |
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. |
open View? |
onFocusSearchFailed(@NonNull focused: View, direction: Int, @NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State) Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView. |
open Unit |
onInitializeAccessibilityEvent(@NonNull event: AccessibilityEvent) |
open Unit |
onInitializeAccessibilityEvent(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull event: AccessibilityEvent) Called by the accessibility delegate to initialize an accessibility event. |
open Unit |
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. |
open Unit |
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. |
open View? |
onInterceptFocusSearch(@NonNull focused: View, direction: Int) This method gives a LayoutManager an opportunity to intercept the initial focus search before the default behavior of |
open Unit |
onItemsAdded(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int) Called when items have been added to the adapter. |
open Unit |
onItemsChanged(@NonNull recyclerView: RecyclerView) Called in response to a call to |
open Unit |
onItemsMoved(@NonNull recyclerView: RecyclerView, from: Int, to: Int, itemCount: Int) Called when an item is moved withing the adapter. |
open Unit |
onItemsRemoved(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int) Called when items have been removed from the adapter. |
open Unit |
onItemsUpdated(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int) Called when items have been changed in the adapter. |
open Unit |
onItemsUpdated(@NonNull recyclerView: RecyclerView, positionStart: Int, itemCount: Int, @Nullable payload: Any?) Called when items have been changed in the adapter and with optional payload. |
open Unit |
onLayoutChildren(recycler: RecyclerView.Recycler!, state: RecyclerView.State!) Lay out all relevant child views from the given adapter. |
open Unit |
onLayoutCompleted(state: RecyclerView.State!) Called after a full layout calculation is finished. |
open Unit |
onMeasure(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, widthSpec: Int, heightSpec: Int) Measure the attached RecyclerView. |
open Boolean |
onRequestChildFocus(@NonNull parent: RecyclerView, @NonNull child: View, @Nullable focused: View?) |
open Boolean |
onRequestChildFocus(@NonNull parent: RecyclerView, @NonNull state: RecyclerView.State, @NonNull child: View, @Nullable focused: View?) Called when a descendant view of the RecyclerView requests focus. |
open Unit |
onRestoreInstanceState(state: Parcelable!) |
open Parcelable? |
Called when the LayoutManager should save its state. |
open Unit |
onScrollStateChanged(state: Int) RecyclerView calls this method to notify LayoutManager that scroll state has changed. |
open Boolean |
performAccessibilityAction(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, action: Int, @Nullable args: Bundle?) Called by AccessibilityDelegate when an action is requested from the RecyclerView. |
open Boolean |
performAccessibilityActionForItem(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State, @NonNull view: View, action: Int, @Nullable args: Bundle?) Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager. |
open Unit |
postOnAnimation(action: Runnable!) Causes the Runnable to execute on the next animation time step. |
open Unit |
Remove all views from the currently attached RecyclerView. |
open Unit |
removeAndRecycleAllViews(@NonNull recycler: RecyclerView.Recycler) Removes all views and recycles them using the given recycler. |
open Unit |
removeAndRecycleView(@NonNull child: View, @NonNull recycler: RecyclerView.Recycler) Remove a child view and recycle it using the given Recycler. |
open Unit |
removeAndRecycleViewAt(index: Int, @NonNull recycler: RecyclerView.Recycler) Remove a child view and recycle it using the given Recycler. |
open Boolean |
removeCallbacks(action: Runnable!) Removes the specified Runnable from the message queue. |
open Unit |
removeDetachedView(@NonNull child: View) Finish removing a view that was previously temporarily |
open Unit |
removeView(child: View!) Remove a view from the currently attached RecyclerView if needed. |
open Unit |
removeViewAt(index: Int) Remove a view from the currently attached RecyclerView if needed. |
open Boolean |
requestChildRectangleOnScreen(@NonNull parent: RecyclerView, @NonNull child: View, @NonNull rect: Rect, immediate: Boolean) Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen. |
open Boolean |
requestChildRectangleOnScreen(@NonNull parent: RecyclerView, @NonNull child: View, @NonNull rect: Rect, immediate: Boolean, focusedChildVisible: Boolean) Requests that the given child of the RecyclerView be positioned onto the screen. |
open Unit |
Calls |
open Unit |
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. |
open Int |
scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler!, state: RecyclerView.State!) Scroll horizontally by dx pixels in screen coordinates and return the distance traveled. |
open Unit |
scrollToPosition(position: Int) Scroll to the specified adapter position. |
open Int |
scrollVerticallyBy(dy: Int, recycler: RecyclerView.Recycler!, state: RecyclerView.State!) Scroll vertically by dy pixels in screen coordinates and return the distance traveled. |
open Unit |
setAutoMeasureEnabled(enabled: Boolean) Defines whether the measuring pass of layout should use the AutoMeasure mechanism of |
Unit |
setItemPrefetchEnabled(enabled: Boolean) Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames. |
open Unit |
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 |
open Unit |
setMeasuredDimension(widthSize: Int, heightSize: Int)
|
open Unit |
setMeasurementCacheEnabled(measurementCacheEnabled: Boolean) Sets whether RecyclerView should use its own measurement cache for the children. |
open Unit |
smoothScrollToPosition(recyclerView: RecyclerView!, state: RecyclerView.State!, position: Int) Smooth scroll to the specified adapter position. |
open Unit |
startSmoothScroll(smoothScroller: RecyclerView.SmoothScroller!) Starts a smooth scroll using the provided |
open Unit |
stopIgnoringView(@NonNull view: View) View can be scrapped and recycled again. |
open Boolean |
Returns whether this LayoutManager supports "predictive item animations". |
Public constructors
<init>
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.
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.Public methods
addDisappearingView
open fun addDisappearingView(child: View!): Unit
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. |
addDisappearingView
open fun addDisappearingView(child: View!, index: Int): Unit
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 |
View!: Index of the view. |
addView
open fun addView(child: View!): Unit
Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a Recycler
using Recycler#getViewForPosition(int)
.
Parameters | |
---|---|
child |
View!: View to add |
addView
open fun addView(child: View!, index: Int): Unit
Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a Recycler
using Recycler#getViewForPosition(int)
.
Parameters | |
---|---|
child |
View!: View to add |
index |
View!: Index to add child at |
assertInLayoutOrScroll
open fun assertInLayoutOrScroll(message: String!): Unit
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. |
See Also
assertNotInLayoutOrScroll
open fun assertNotInLayoutOrScroll(message: String!): Unit
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. |
See Also
attachView
open fun attachView(@NonNull child: View, index: Int, lp: RecyclerView.LayoutParams!): Unit
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 |
View: Intended child index for child |
lp |
View: LayoutParams for child |
attachView
open fun attachView(@NonNull child: View, index: Int): Unit
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 |
View: Intended child index for child |
attachView
open fun attachView(@NonNull child: View): Unit
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 |
calculateItemDecorationsForChild
open fun calculateItemDecorationsForChild(@NonNull child: View, @NonNull outRect: Rect): Unit
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 |
View: The Rect to hold result values |
canScrollHorizontally
open fun canScrollHorizontally(): Boolean
Query if horizontal scrolling is currently supported. The default implementation returns false.
Return | |
---|---|
Boolean: True if this LayoutManager can scroll the current contents horizontally |
canScrollVertically
open fun canScrollVertically(): Boolean
Query if vertical scrolling is currently supported. The default implementation returns false.
Return | |
---|---|
Boolean: True if this LayoutManager can scroll the current contents vertically |
checkLayoutParams
open fun checkLayoutParams(lp: RecyclerView.LayoutParams!): Boolean
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 |
Return | |
---|---|
Boolean: true if this LayoutParams object is valid, false otherwise |
chooseSize
open static 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.
Parameters | |
---|---|
spec |
Int: The measureSpec |
desired |
Int: The preferred measurement |
min |
Int: The minimum value |
Return | |
---|---|
Int: A size that fits to the given specs |
collectAdjacentPrefetchPositions
open fun collectAdjacentPrefetchPositions(dx: Int, dy: Int, state: RecyclerView.State!, layoutPrefetchRegistry: RecyclerView.LayoutManager.LayoutPrefetchRegistry!): Unit
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 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 |
Int: State of RecyclerView |
layoutPrefetchRegistry |
Int: PrefetchRegistry to add prefetch entries into. |
collectInitialPrefetchPositions
open fun collectInitialPrefetchPositions(adapterItemCount: Int, layoutPrefetchRegistry: RecyclerView.LayoutManager.LayoutPrefetchRegistry!): Unit
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 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 |
Int: PrefetchRegistry to add prefetch entries into. |
computeHorizontalScrollExtent
open fun computeHorizontalScrollExtent(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The horizontal extent of the scrollbar's thumb |
computeHorizontalScrollOffset
open fun computeHorizontalScrollOffset(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The horizontal offset of the scrollbar's thumb |
computeHorizontalScrollRange
open fun computeHorizontalScrollRange(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The total horizontal range represented by the vertical scrollbar |
computeVerticalScrollExtent
open fun computeVerticalScrollExtent(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The vertical extent of the scrollbar's thumb |
computeVerticalScrollOffset
open fun computeVerticalScrollOffset(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The vertical offset of the scrollbar's thumb |
computeVerticalScrollRange
open fun computeVerticalScrollRange(@NonNull state: RecyclerView.State): Int
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 |
Return | |
---|---|
Int: The total vertical range represented by the vertical scrollbar |
detachAndScrapAttachedViews
open fun detachAndScrapAttachedViews(@NonNull recycler: RecyclerView.Recycler): Unit
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
open fun detachAndScrapView(@NonNull child: View, @NonNull recycler: RecyclerView.Recycler): Unit
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 |
View: Recycler to deposit the new scrap view into |
detachAndScrapViewAt
open fun detachAndScrapViewAt(index: Int, @NonNull recycler: RecyclerView.Recycler): Unit
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 |
Int: Recycler to deposit the new scrap view into |
detachView
open fun detachView(@NonNull child: View): Unit
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
open fun detachViewAt(index: Int): Unit
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
open fun endAnimation(view: View!): Unit
Ends all animations on the view created by the ItemAnimator
.
Parameters | |
---|---|
view |
View!: The View for which the animations should be ended. |
findContainingItemView
@Nullable open fun findContainingItemView(@NonNull view: View): View?
Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the 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. |
Return | |
---|---|
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
@Nullable open fun findViewByPosition(position: Int): View?
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 |
Return | |
---|---|
View?: The child view that represents the given position or null if the position is not laid out |
generateDefaultLayoutParams
abstract fun generateDefaultLayoutParams(): RecyclerView.LayoutParams!
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)
.
Return | |
---|---|
RecyclerView.LayoutParams!: A new LayoutParams for a child view |
generateLayoutParams
open fun generateLayoutParams(lp: LayoutParams!): RecyclerView.LayoutParams!
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 |
LayoutParams!: Source LayoutParams object to copy values from |
Return | |
---|---|
RecyclerView.LayoutParams!: a new LayoutParams object |
generateLayoutParams
open fun generateLayoutParams(c: Context!, attrs: AttributeSet!): RecyclerView.LayoutParams!
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 |
Context!: AttributeSet describing the supplied arguments |
Return | |
---|---|
RecyclerView.LayoutParams!: a new LayoutParams object |
getBaseline
open fun getBaseline(): Int
Returns offset of the RecyclerView's text baseline from the its top boundary.
Return | |
---|---|
Int: The offset of the RecyclerView's text baseline from the its top boundary; -1 if there is no baseline. |
getBottomDecorationHeight
open fun getBottomDecorationHeight(@NonNull child: View): Int
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 |
Return | |
---|---|
Int: The total height of item decorations applied to the child's bottom. |
getChildAt
@Nullable open fun getChildAt(index: Int): View?
Return the child view at the given index
Parameters | |
---|---|
index |
Int: Index of child to return |
Return | |
---|---|
View?: Child view at index |
getChildCount
open fun getChildCount(): Int
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.
Return | |
---|---|
Int: Number of attached children |
getChildMeasureSpec
open static fungetChildMeasureSpec(parentSize: Int, padding: Int, childDimension: Int, canScroll: Boolean): Int
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 |
Int: true if the parent RecyclerView can scroll in this dimension |
Return | |
---|---|
Int: a MeasureSpec value for the child view |
getChildMeasureSpec
open static 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.
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 |
Int: true if the parent RecyclerView can scroll in this dimension |
Return | |
---|---|
Int: a MeasureSpec value for the child view |
getClipToPadding
open fun getClipToPadding(): Boolean
Check if the RecyclerView is configured to clip child views to its padding.
Return | |
---|---|
Boolean: true if this RecyclerView clips children to its padding, false otherwise |
getColumnCountForAccessibility
open fun getColumnCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
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.Recycler: The current state of RecyclerView |
Return | |
---|---|
Int: The number of rows in LayoutManager for accessibility. |
getDecoratedBottom
open fun getDecoratedBottom(@NonNull child: View): Int
Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations
.
Parameters | |
---|---|
child |
View: Child to query |
Return | |
---|---|
Int: Child bottom edge with offsets applied |
See Also
getDecoratedBoundsWithMargins
open fun getDecoratedBoundsWithMargins(@NonNull view: View, @NonNull outBounds: Rect): Unit
Returns the bounds of the view including its decoration and margins.
Parameters | |
---|---|
view |
View: The view element to check |
outBounds |
View: A rect that will receive the bounds of the element including its decoration and margins. |
getDecoratedLeft
open fun getDecoratedLeft(@NonNull child: View): Int
Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations
.
Parameters | |
---|---|
child |
View: Child to query |
Return | |
---|---|
Int: Child left edge with offsets applied |
See Also
getDecoratedMeasuredHeight
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
.
Parameters | |
---|---|
child |
View: Child view to query |
Return | |
---|---|
Int: child's measured height plus ItemDecoration insets |
See Also
getDecoratedMeasuredWidth
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
.
Parameters | |
---|---|
child |
View: Child view to query |
Return | |
---|---|
Int: child's measured width plus ItemDecoration insets |
See Also
getDecoratedRight
open fun getDecoratedRight(@NonNull child: View): Int
Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations
.
Parameters | |
---|---|
child |
View: Child to query |
Return | |
---|---|
Int: Child right edge with offsets applied |
See Also
getDecoratedTop
open fun getDecoratedTop(@NonNull child: View): Int
Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations
.
Parameters | |
---|---|
child |
View: Child to query |
Return | |
---|---|
Int: Child top edge with offsets applied |
See Also
getFocusedChild
@Nullable open fun getFocusedChild(): View?
Returns the item View which has or contains focus.
Return | |
---|---|
View?: A direct child of RecyclerView which has focus or contains the focused child. |
getHeight
@Px open fun getHeight(): Int
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 android.view.View.MeasureSpec
height if the 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.
Return | |
---|---|
Int: Height in pixels |
getHeightMode
open fun getHeightMode(): Int
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.
Return | |
---|---|
Int: Height measure spec mode |
See Also
getItemCount
open fun getItemCount(): Int
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 State
is available, you should use State#getItemCount()
instead. For more details, check the documentation for State#getItemCount()
.
Return | |
---|---|
Int: The number of items in the bound adapter |
See Also
getItemViewType
open fun getItemViewType(@NonNull view: View): Int
Returns the View type defined by the adapter.
Parameters | |
---|---|
view |
View: The view to query |
Return | |
---|---|
Int: The type of the view assigned by the adapter. |
getLayoutDirection
open fun getLayoutDirection(): Int
Returns the resolved layout direction for this RecyclerView.
Return | |
---|---|
Int: androidx.core.view.ViewCompat#LAYOUT_DIRECTION_RTL if the layout direction is RTL or returns androidx.core.view.ViewCompat#LAYOUT_DIRECTION_LTR if the layout direction is not RTL. |
getLeftDecorationWidth
open fun getLeftDecorationWidth(@NonNull child: View): Int
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 |
Return | |
---|---|
Int: The total width of item decorations applied to the child's left. |
getMinimumHeight
@Px open fun getMinimumHeight(): Int
Return | |
---|---|
Int: The host RecyclerView's View#getMinimumHeight() |
getMinimumWidth
@Px open fun getMinimumWidth(): Int
Return | |
---|---|
Int: The host RecyclerView's View#getMinimumWidth() |
getPaddingBottom
@Px open fun getPaddingBottom(): Int
Return the bottom padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPaddingEnd
@Px open fun getPaddingEnd(): Int
Return the end padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPaddingLeft
@Px open fun getPaddingLeft(): Int
Return the left padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPaddingRight
@Px open fun getPaddingRight(): Int
Return the right padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPaddingStart
@Px open fun getPaddingStart(): Int
Return the start padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPaddingTop
@Px open fun getPaddingTop(): Int
Return the top padding of the parent RecyclerView
Return | |
---|---|
Int: Padding in pixels |
getPosition
open fun getPosition(@NonNull view: View): Int
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 |
Return | |
---|---|
Int: The adapter position of the item which is rendered by this View. |
getProperties
open static 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. android.R.attr#orientation
androidx.recyclerview.R.attr#spanCount androidx.recyclerview.R.attr#reverseLayout androidx.recyclerview.R.attr#stackFromEnd
Return | |
---|---|
RecyclerView.LayoutManager.Properties!: an object containing the properties as specified in the attrs. |
getRightDecorationWidth
open fun getRightDecorationWidth(@NonNull child: View): Int
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 |
Return | |
---|---|
Int: The total width of item decorations applied to the child's right. |
getRowCountForAccessibility
open fun getRowCountForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
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.Recycler: The current state of RecyclerView |
Return | |
---|---|
Int: The number of rows in LayoutManager for accessibility. |
getSelectionModeForAccessibility
open fun getSelectionModeForAccessibility(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Int
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.Recycler: The current state of RecyclerView |
Return | |
---|---|
Int: Selection mode for accessibility. Default implementation returns AccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_NONE . |
getTopDecorationHeight
open fun getTopDecorationHeight(@NonNull child: View): Int
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 |
Return | |
---|---|
Int: The total height of item decorations applied to the child's top. |
getTransformedBoundingBox
open fun getTransformedBoundingBox(@NonNull child: View, includeDecorInsets: Boolean, @NonNull out: Rect): Unit
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 |
View: True if the decor insets should be included in the bounding box |
out |
View: The rectangle into which the output will be written. |
getWidth
@Px open fun getWidth(): Int
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 android.view.View.MeasureSpec
width if the 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.
Return | |
---|---|
Int: Width in pixels |
getWidthMode
open fun getWidthMode(): Int
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.
Return | |
---|---|
Int: Width measure spec mode |
See Also
hasFocus
open fun hasFocus(): Boolean
Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.
Return | |
---|---|
Boolean: true if the RecyclerView has or contains focus |
See Also
ignoreView
open fun ignoreView(@NonNull view: View): Unit
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. |
See Also
isAttachedToWindow
open fun isAttachedToWindow(): Boolean
Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.
Return | |
---|---|
Boolean: True if this LayoutManager is controlling a RecyclerView and the RecyclerView is attached to window. |
isAutoMeasureEnabled
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 LayoutManager#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, LayoutManager#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 LayoutManager#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:
- When
RecyclerView#onMeasure(int, int)
is called, if the provided measure specs both have a mode ofView.MeasureSpec#EXACTLY
, RecyclerView will set its measured dimensions accordingly and return, allowing layout to continue as normal (Actually, RecyclerView will callLayoutManager#onMeasure(Recycler, State, int, int)
for backwards compatibility reasons but it should not be overridden if AutoMeasure is being used). - 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 callonLayoutChildren(Recycler, State)
withState#isPreLayout()
set totrue
. At this stage,getWidth()
andgetHeight()
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)
withState#isMeasuring()
set totrue
andState#isPreLayout()
set tofalse
. The LayoutManager can access the measurement specs viagetHeight()
,getHeightMode()
,getWidth()
andgetWidthMode()
. - 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. - Any following calls to
RecyclerView#onMeasure(int, int)
will runonLayoutChildren(Recycler, State)
withState#isMeasuring()
set totrue
andState#isPreLayout()
set tofalse
. 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 eachonLayoutChildren(Recycler, State)
call as if it is the last one. - When measure is complete and RecyclerView's
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 callonLayoutChildren(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. - Finally, animations are calculated and run as usual.
Return | |
---|---|
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 LayoutManager#onMeasure(Recycler, State, int, int) . |
isFocused
open fun isFocused(): Boolean
Returns true if the RecyclerView this LayoutManager is bound to has focus.
Return | |
---|---|
Boolean: True if the RecyclerView has focus, false otherwise. |
See Also
isItemPrefetchEnabled
fun isItemPrefetchEnabled(): Boolean
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.
Return | |
---|---|
Boolean: true if item prefetch is enabled, false otherwise |
See Also
isLayoutHierarchical
open fun isLayoutHierarchical(@NonNull recycler: RecyclerView.Recycler, @NonNull state: RecyclerView.State): Boolean
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.Recycler: The current state of RecyclerView |
Return | |
---|---|
Boolean: True if layout is hierarchical. |
isMeasurementCacheEnabled
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. It is on by default but it can be turned off via setMeasurementCacheEnabled(boolean)
.
Return | |
---|---|
Boolean: True if measurement cache is enabled, false otherwise. |
See Also
isSmoothScrolling
open fun isSmoothScrolling(): Boolean
Return | |
---|---|
Boolean: true if RecyclerView is currently in the state of smooth scrolling. |
isViewPartiallyVisible
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. 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 |
View: 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 |
View: If the view's endpoint intersection with RV's start of end bounds is enough to consider it partially visible, false otherwise. |
Return | |
---|---|
Boolean: True if the given child is partially or fully visible, false otherwise. |
layoutDecorated
open fun layoutDecorated(@NonNull child: View, left: Int, top: Int, right: Int, bottom: Int): Unit
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:
layoutDecoratedWithMargins(View, int, int, int, int)
getDecoratedBoundsWithMargins(View, Rect)
measureChild(View, int, int)
measureChildWithMargins(View, int, int)
getDecoratedLeft(View)
getDecoratedTop(View)
getDecoratedRight(View)
getDecoratedBottom(View)
getDecoratedMeasuredWidth(View)
getDecoratedMeasuredHeight(View)
Parameters | |
---|---|
child |
View: Child to lay out |
left |
View: Left edge, with item decoration insets included |
top |
View: Top edge, with item decoration insets included |
right |
View: Right edge, with item decoration insets included |
bottom |
View: Bottom edge, with item decoration insets included |
layoutDecoratedWithMargins
open fun layoutDecoratedWithMargins(@NonNull child: View, left: Int, top: Int, right: Int, bottom: Int): Unit
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:
layoutDecorated(View, int, int, int, int)
measureChild(View, int, int)
measureChildWithMargins(View, int, int)
getDecoratedLeft(View)
getDecoratedTop(View)
getDecoratedRight(View)
getDecoratedBottom(View)
getDecoratedMeasuredWidth(View)
getDecoratedMeasuredHeight(View)
Parameters | |
---|---|
child |
View: Child to lay out |
left |
View: Left edge, with item decoration insets and left margin included |
top |
View: Top edge, with item decoration insets and top margin included |
right |
View: Right edge, with item decoration insets and right margin included |
bottom |
View: Bottom edge, with item decoration insets and bottom margin included |
measureChild
open fun measureChild(@NonNull child: View, widthUsed: Int, heightUsed: Int): Unit
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 |
View: Width in pixels currently consumed by other views, if relevant |
heightUsed |
View: Height in pixels currently consumed by other views, if relevant |
measureChildWithMargins
open fun measureChildWithMargins(@NonNull child: View, widthUsed: Int, heightUsed: Int): Unit
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 |
View: Width in pixels currently consumed by other views, if relevant |
heightUsed |
View: Height in pixels currently consumed by other views, if relevant |
moveView
open fun moveView(fromIndex: Int, toIndex: Int): Unit
Moves a View from one position to another.
Parameters | |
---|---|
fromIndex |
Int: The View's initial index |
toIndex |
Int: The View's target index |
offsetChildrenHorizontal
open fun offsetChildrenHorizontal(@Px dx: Int): Unit
Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.
Parameters | |
---|---|
dx |
Int: Pixels to offset by |
offsetChildrenVertical
open fun offsetChildrenVertical(@Px dy: Int): Unit
Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.
Parameters | |
---|---|
dy |
Int: Pixels to offset by |
onAdapterChanged
open fun onAdapterChanged(@Nullable oldAdapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?, @Nullable newAdapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>?): Unit
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 |
RecyclerView.Adapter<RecyclerView.ViewHolder!>?: The previous adapter instance. Will be null if there was previously no adapter. |
newAdapter |
RecyclerView.Adapter<RecyclerView.ViewHolder!>?: The new adapter instance. Might be null if setAdapter(RecyclerView.Adapter) is called with null . |
onAddFocusables
open fun onAddFocusables(@NonNull recyclerView: RecyclerView, @NonNull views: ArrayList<View!>, direction: Int, focusableMode: Int): Boolean
Called to populate focusable views within the RecyclerView.
The LayoutManager implementation should return true
if the default behavior of ViewGroup#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 |
RecyclerView: List of output views. This method should add valid focusable views to this list. |
direction |
RecyclerView: One of View#FOCUS_UP , View#FOCUS_DOWN , View#FOCUS_LEFT , View#FOCUS_RIGHT , View#FOCUS_BACKWARD , View#FOCUS_FORWARD |
focusableMode |
RecyclerView: The type of focusables to be added. |
Return | |
---|---|
Boolean: true to suppress the default behavior, false to add default focusables after this method returns. |
onAttachedToWindow
@CallSuper open fun onAttachedToWindow(view: RecyclerView!): Unit
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
open funonDetachedFromWindow(view: RecyclerView!): Unit
Deprecated: override onDetachedFromWindow(RecyclerView, Recycler)