public abstract static class RecyclerView.LayoutManager extends Object
LayoutManager
is responsible for measuring and positioning item views
within a RecyclerView
as well as determining the policy for when to recycle
item views that are no longer visible to the user. By changing the LayoutManager
a RecyclerView
can be used to implement a standard vertically scrolling list,
a uniform grid, staggered grids, horizontally scrolling collections and more. Several stock
layout managers are provided for general use.
If the LayoutManager specifies a default constructor or one with the signature
(Context
, AttributeSet
, int
, int
), RecyclerView will
instantiate and set the LayoutManager when being inflated. Most used properties can
be then obtained from getProperties(Context, AttributeSet, int, int)
. In case
a LayoutManager specifies both constructors, the non-default constructor will take
precedence.Modifier and Type | Class and Description |
---|---|
static class |
RecyclerView.LayoutManager.Properties
Some general properties that a LayoutManager may want to use.
|
Constructor and Description |
---|
LayoutManager() |
Modifier and Type | Method and Description |
---|---|
void |
addDisappearingView(View child)
To be called only during
#onLayoutChildren(Recycler, State) to add a view
to the layout that is known to be going away, either because it has been
removed or because it is actually not in the
visible portion of the container but is being laid out in order to inform RecyclerView
in how to animate the item out of view. |
void |
addDisappearingView(View child,
int index)
To be called only during
#onLayoutChildren(Recycler, State) to add a view
to the layout that is known to be going away, either because it has been
removed or because it is actually not in the
visible portion of the container but is being laid out in order to inform RecyclerView
in how to animate the item out of view. |
void |
addView(View child)
Add a view to the currently attached RecyclerView if needed.
|
void |
addView(View child,
int index)
Add a view to the currently attached RecyclerView if needed.
|
void |
assertInLayoutOrScroll(String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
IllegalStateException if it is not. |
void |
assertNotInLayoutOrScroll(String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
IllegalStateException if it is. |
void |
attachView(View child)
Reattach a previously
detached view. |
void |
attachView(View child,
int index)
Reattach a previously
detached view. |
void |
attachView(View child,
int index,
RecyclerView.LayoutParams lp)
Reattach a previously
detached view. |
void |
calculateItemDecorationsForChild(View child,
Rect outRect)
Calculates the item decor insets applied to the given child and updates the provided
Rect instance with the inset values.
|
boolean |
canScrollHorizontally()
Query if horizontal scrolling is currently supported.
|
boolean |
canScrollVertically()
Query if vertical scrolling is currently supported.
|
boolean |
checkLayoutParams(RecyclerView.LayoutParams lp)
Determines the validity of the supplied LayoutParams object.
|
static int |
chooseSize(int spec,
int desired,
int min)
Chooses a size from the given specs and parameters that is closest to the desired size
and also complies with the spec.
|
int |
computeHorizontalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
int |
computeHorizontalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
int |
computeHorizontalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
int |
computeVerticalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
int |
computeVerticalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
int |
computeVerticalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars.
|
void |
detachAndScrapAttachedViews(RecyclerView.Recycler recycler)
Temporarily detach and scrap all currently attached child views.
|
void |
detachAndScrapView(View child,
RecyclerView.Recycler recycler)
Detach a child view and add it to a
Recycler's scrap heap. |
void |
detachAndScrapViewAt(int index,
RecyclerView.Recycler recycler)
Detach a child view and add it to a
Recycler's scrap heap. |
void |
detachView(View child)
Temporarily detach a child view.
|
void |
detachViewAt(int index)
Temporarily detach a child view.
|
void |
endAnimation(View view)
Ends all animations on the view created by the
RecyclerView.ItemAnimator . |
View |
findContainingItemView(View view)
Traverses the ancestors of the given view and returns the item view that contains it
and also a direct child of the LayoutManager.
|
View |
findViewByPosition(int position)
Finds the view which represents the given adapter position.
|
abstract RecyclerView.LayoutParams |
generateDefaultLayoutParams()
Create a default
LayoutParams object for a child of the RecyclerView. |
RecyclerView.LayoutParams |
generateLayoutParams(Context c,
AttributeSet attrs)
Create a LayoutParams object suitable for this LayoutManager from
an inflated layout resource.
|
RecyclerView.LayoutParams |
generateLayoutParams(ViewGroup.LayoutParams lp)
Create a LayoutParams object suitable for this LayoutManager, copying relevant
values from the supplied LayoutParams object if possible.
|
int |
getBaseline()
Returns offset of the RecyclerView's text baseline from the its top boundary.
|
int |
getBottomDecorationHeight(View child)
Returns the total height of item decorations applied to child's bottom.
|
View |
getChildAt(int index)
Return the child view at the given index
|
int |
getChildCount()
Return the current number of child views attached to the parent RecyclerView.
|
static int |
getChildMeasureSpec(int parentSize,
int padding,
int childDimension,
boolean canScroll)
Deprecated.
|
static int |
getChildMeasureSpec(int parentSize,
int parentMode,
int padding,
int childDimension,
boolean canScroll)
Calculate a MeasureSpec value for measuring a child view in one dimension.
|
boolean |
getClipToPadding()
Check if the RecyclerView is configured to clip child views to its padding.
|
int |
getColumnCountForAccessibility(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns the number of columns for accessibility.
|
int |
getDecoratedBottom(View child)
Returns the bottom edge of the given child view within its parent, offset by any applied
ItemDecorations . |
void |
getDecoratedBoundsWithMargins(View view,
Rect outBounds)
Returns the bounds of the view including its decoration and margins.
|
int |
getDecoratedLeft(View child)
Returns the left edge of the given child view within its parent, offset by any applied
ItemDecorations . |
int |
getDecoratedMeasuredHeight(View child)
Returns the measured height of the given child, plus the additional size of
any insets applied by
ItemDecorations . |
int |
getDecoratedMeasuredWidth(View child)
Returns the measured width of the given child, plus the additional size of
any insets applied by
ItemDecorations . |
int |
getDecoratedRight(View child)
Returns the right edge of the given child view within its parent, offset by any applied
ItemDecorations . |
int |
getDecoratedTop(View child)
Returns the top edge of the given child view within its parent, offset by any applied
ItemDecorations . |
View |
getFocusedChild()
Returns the item View which has or contains focus.
|
int |
getHeight()
Return the height of the parent RecyclerView
|
int |
getHeightMode()
Return the height measurement spec mode of the RecyclerView.
|
int |
getItemCount()
Returns the number of items in the adapter bound to the parent RecyclerView.
|
int |
getItemViewType(View view)
Returns the View type defined by the adapter.
|
int |
getLayoutDirection()
Returns the resolved layout direction for this RecyclerView.
|
int |
getLeftDecorationWidth(View child)
Returns the total width of item decorations applied to child's left.
|
int |
getMinimumHeight() |
int |
getMinimumWidth() |
int |
getPaddingBottom()
Return the bottom padding of the parent RecyclerView
|
int |
getPaddingEnd()
Return the end padding of the parent RecyclerView
|
int |
getPaddingLeft()
Return the left padding of the parent RecyclerView
|
int |
getPaddingRight()
Return the right padding of the parent RecyclerView
|
int |
getPaddingStart()
Return the start padding of the parent RecyclerView
|
int |
getPaddingTop()
Return the top padding of the parent RecyclerView
|
int |
getPosition(View view)
Returns the adapter position of the item represented by the given View.
|
static RecyclerView.LayoutManager.Properties |
getProperties(Context context,
AttributeSet attrs,
int defStyleAttr,
int defStyleRes)
Parse the xml attributes to get the most common properties used by layout managers.
|
int |
getRightDecorationWidth(View child)
Returns the total width of item decorations applied to child's right.
|
int |
getRowCountForAccessibility(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns the number of rows for accessibility.
|
int |
getSelectionModeForAccessibility(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns the selection mode for accessibility.
|
int |
getTopDecorationHeight(View child)
Returns the total height of item decorations applied to child's top.
|
void |
getTransformedBoundingBox(View child,
boolean includeDecorInsets,
Rect out)
Calculates the bounding box of the View while taking into account its matrix changes
(translation, scale etc) with respect to the RecyclerView.
|
int |
getWidth()
Return the width of the parent RecyclerView
|
int |
getWidthMode()
Return the width measurement spec mode of the RecyclerView.
|
boolean |
hasFocus()
Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.
|
void |
ignoreView(View view)
Flags a view so that it will not be scrapped or recycled.
|
boolean |
isAttachedToWindow()
Returns whether LayoutManager is currently attached to a RecyclerView which is attached
to a window.
|
boolean |
isAutoMeasureEnabled()
Returns whether the LayoutManager uses the automatic measurement API or not.
|
boolean |
isFocused()
Returns true if the RecyclerView this LayoutManager is bound to has focus.
|
boolean |
isItemPrefetchEnabled()
Sets whether the LayoutManager should be queried for views outside of
its viewport while the UI thread is idle between frames.
|
boolean |
isLayoutHierarchical(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns whether layout is hierarchical or not to be used for accessibility.
|
boolean |
isMeasurementCacheEnabled()
In addition to the View Framework's measurement cache, RecyclerView uses its own
additional measurement cache for its children to avoid re-measuring them when not
necessary.
|
boolean |
isSmoothScrolling() |
void |
layoutDecorated(View child,
int left,
int top,
int right,
int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current
ItemDecorations . |
void |
layoutDecoratedWithMargins(View child,
int left,
int top,
int right,
int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current
ItemDecorations and margins. |
void |
measureChild(View child,
int widthUsed,
int heightUsed)
Measure a child view using standard measurement policy, taking the padding
of the parent RecyclerView and any added item decorations into account.
|
void |
measureChildWithMargins(View child,
int widthUsed,
int heightUsed)
Measure a child view using standard measurement policy, taking the padding
of the parent RecyclerView, any added item decorations and the child margins
into account.
|
void |
moveView(int fromIndex,
int toIndex)
Moves a View from one position to another.
|
void |
offsetChildrenHorizontal(int dx)
Offset all child views attached to the parent RecyclerView by dx pixels along
the horizontal axis.
|
void |
offsetChildrenVertical(int dy)
Offset all child views attached to the parent RecyclerView by dy pixels along
the vertical axis.
|
void |
onAdapterChanged(RecyclerView.Adapter oldAdapter,
RecyclerView.Adapter newAdapter)
Called if the RecyclerView this LayoutManager is bound to has a different adapter set.
|
boolean |
onAddFocusables(RecyclerView recyclerView,
ArrayList<View> views,
int direction,
int focusableMode)
Called to populate focusable views within the RecyclerView.
|
void |
onAttachedToWindow(RecyclerView view)
Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView
is attached to a window.
|
void |
onDetachedFromWindow(RecyclerView view)
Deprecated.
override
#onDetachedFromWindow(RecyclerView, Recycler) |
void |
onDetachedFromWindow(RecyclerView view,
RecyclerView.Recycler recycler)
Called when this LayoutManager is detached from its parent RecyclerView or when
its parent RecyclerView is detached from its window.
|
View |
onFocusSearchFailed(View focused,
int direction,
RecyclerView.Recycler recycler,
RecyclerView.State state)
Called when searching for a focusable view in the given direction has failed
for the current content of the RecyclerView.
|
void |
onInitializeAccessibilityEvent(AccessibilityEvent event) |
void |
onInitializeAccessibilityEvent(RecyclerView.Recycler recycler,
RecyclerView.State state,
AccessibilityEvent event)
Called by the accessibility delegate to initialize an accessibility event.
|
void |
onInitializeAccessibilityNodeInfo(RecyclerView.Recycler recycler,
RecyclerView.State state,
AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the information about the current layout should
be populated.
|
void |
onInitializeAccessibilityNodeInfoForItem(RecyclerView.Recycler recycler,
RecyclerView.State state,
View host,
AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the accessibility information for a specific
item should be populated.
|
View |
onInterceptFocusSearch(View focused,
int direction)
This method gives a LayoutManager an opportunity to intercept the initial focus search
before the default behavior of
FocusFinder is used. |
void |
onItemsAdded(RecyclerView recyclerView,
int positionStart,
int itemCount)
Called when items have been added to the adapter.
|
void |
onItemsChanged(RecyclerView recyclerView)
Called when
RecyclerView.Adapter.notifyDataSetChanged() is triggered instead of giving
detailed information on what has actually changed. |
void |
onItemsMoved(RecyclerView recyclerView,
int from,
int to,
int itemCount)
Called when an item is moved withing the adapter.
|
void |
onItemsRemoved(RecyclerView recyclerView,
int positionStart,
int itemCount)
Called when items have been removed from the adapter.
|
void |
onItemsUpdated(RecyclerView recyclerView,
int positionStart,
int itemCount)
Called when items have been changed in the adapter.
|
void |
onItemsUpdated(RecyclerView recyclerView,
int positionStart,
int itemCount,
Object payload)
Called when items have been changed in the adapter and with optional payload.
|
void |
onLayoutChildren(RecyclerView.Recycler recycler,
RecyclerView.State state)
Lay out all relevant child views from the given adapter.
|
void |
onLayoutCompleted(RecyclerView.State state)
Called after a full layout calculation is finished.
|
void |
onMeasure(RecyclerView.Recycler recycler,
RecyclerView.State state,
int widthSpec,
int heightSpec)
Measure the attached RecyclerView.
|
boolean |
onRequestChildFocus(RecyclerView parent,
RecyclerView.State state,
View child,
View focused)
Called when a descendant view of the RecyclerView requests focus.
|
boolean |
onRequestChildFocus(RecyclerView parent,
View child,
View focused)
Deprecated.
Use
#onRequestChildFocus(RecyclerView, State, View, View) |
void |
onRestoreInstanceState(Parcelable state) |
Parcelable |
onSaveInstanceState()
Called when the LayoutManager should save its state.
|
void |
onScrollStateChanged(int state)
RecyclerView calls this method to notify LayoutManager that scroll state has changed.
|
boolean |
performAccessibilityAction(RecyclerView.Recycler recycler,
RecyclerView.State state,
int action,
Bundle args)
Called by AccessibilityDelegate when an action is requested from the RecyclerView.
|
boolean |
performAccessibilityActionForItem(RecyclerView.Recycler recycler,
RecyclerView.State state,
View view,
int action,
Bundle args)
Called by AccessibilityDelegate when an accessibility action is requested on one of the
children of LayoutManager.
|
void |
postOnAnimation(Runnable action)
Causes the Runnable to execute on the next animation time step.
|
void |
removeAllViews()
Remove all views from the currently attached RecyclerView.
|
void |
removeAndRecycleAllViews(RecyclerView.Recycler recycler)
Removes all views and recycles them using the given recycler.
|
void |
removeAndRecycleView(View child,
RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler.
|
void |
removeAndRecycleViewAt(int index,
RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler.
|
boolean |
removeCallbacks(Runnable action)
Removes the specified Runnable from the message queue.
|
void |
removeDetachedView(View child)
Finish removing a view that was previously temporarily
detached . |
void |
removeView(View child)
Remove a view from the currently attached RecyclerView if needed.
|
void |
removeViewAt(int index)
Remove a view from the currently attached RecyclerView if needed.
|
boolean |
requestChildRectangleOnScreen(RecyclerView parent,
View child,
Rect rect,
boolean immediate)
Called when a child of the RecyclerView wants a particular rectangle to be positioned
onto the screen.
|
void |
requestLayout()
Calls
RecyclerView#requestLayout on the underlying RecyclerView |
void |
requestSimpleAnimationsInNextLayout()
A LayoutManager can call this method to force RecyclerView to run simple animations in
the next layout pass, even if there is not any trigger to do so.
|
int |
scrollHorizontallyBy(int dx,
RecyclerView.Recycler recycler,
RecyclerView.State state)
Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.
|
void |
scrollToPosition(int position)
Scroll to the specified adapter position.
|
int |
scrollVerticallyBy(int dy,
RecyclerView.Recycler recycler,
RecyclerView.State state)
Scroll vertically by dy pixels in screen coordinates and return the distance traveled.
|
void |
setAutoMeasureEnabled(boolean enabled)
Defines whether the layout should be measured by the RecyclerView or the LayoutManager
wants to handle the layout measurements itself.
|
void |
setItemPrefetchEnabled(boolean enabled)
Sets whether the LayoutManager should be queried for views outside of
its viewport while the UI thread is idle between frames.
|
void |
setMeasuredDimension(int widthSize,
int heightSize)
Set the measured dimensions of the
host RecyclerView. |
void |
setMeasuredDimension(Rect childrenBounds,
int wSpec,
int hSpec)
Sets the measured dimensions from the given bounding box of the children and the
measurement specs that were passed into
RecyclerView.onMeasure(int, int) . |
void |
setMeasurementCacheEnabled(boolean measurementCacheEnabled)
Sets whether RecyclerView should use its own measurement cache for the children.
|
void |
smoothScrollToPosition(RecyclerView recyclerView,
RecyclerView.State state,
int position)
Smooth scroll to the specified adapter position.
|
void |
startSmoothScroll(RecyclerView.SmoothScroller smoothScroller)
Starts a smooth scroll using the provided SmoothScroller.
|
void |
stopIgnoringView(View view)
View can be scrapped and recycled again.
|
boolean |
supportsPredictiveItemAnimations()
Returns whether this LayoutManager supports automatic item animations.
|
public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)
RecyclerView.onMeasure(int, int)
. It is
called after the RecyclerView calls
LayoutManager#onLayoutChildren(Recycler, State)
during a measurement pass.
This method should call setMeasuredDimension(int, int)
.
The default implementation adds the RecyclerView's padding to the given bounding box then caps the value to be within the given measurement specs.
This method is only called if the LayoutManager opted into the auto measurement API.
childrenBounds
- The bounding box of all childrenwSpec
- The widthMeasureSpec that was passed into the RecyclerView.hSpec
- The heightMeasureSpec that was passed into the RecyclerView.setAutoMeasureEnabled(boolean)
public void requestLayout()
RecyclerView#requestLayout
on the underlying RecyclerViewpublic void assertInLayoutOrScroll(String message)
IllegalStateException
if it is not.message
- The message for the exception. Can be null.assertNotInLayoutOrScroll(String)
public static int chooseSize(int spec, int desired, int min)
spec
- The measureSpecdesired
- The preferred measurementmin
- The minimum valuepublic void assertNotInLayoutOrScroll(String message)
IllegalStateException
if it is.message
- The message for the exception. Can be null.assertInLayoutOrScroll(String)
public void setAutoMeasureEnabled(boolean enabled)
This method is usually called by the LayoutManager with value true
if it wants
to support WRAP_CONTENT. If you are using a public LayoutManager but want to customize
the measurement logic, you can call this method with false
and override
RecyclerView.onMeasure(int, int)
to implement your custom measurement logic.
AutoMeasure is a convenience mechanism for LayoutManagers to easily wrap their content or
handle various specs provided by the RecyclerView's parent.
It works by calling LayoutManager#onLayoutChildren(Recycler, State)
during an
RecyclerView.onMeasure(int, int)
call, then calculating desired dimensions based
on children's positions. It does this while supporting all existing animation
capabilities of the RecyclerView.
AutoMeasure works as follows:
setAutoMeasureEnabled(true)
to enable it. All of
the framework LayoutManagers use auto-measure
.RecyclerView.onMeasure(int, int)
is called, if the provided specs are
exact, RecyclerView will only call LayoutManager's onMeasure
and return without
doing any layout calculation.EXACT
, the RecyclerView will start the
layout process in onMeasure
call. It will process all pending Adapter updates and
decide whether to run a predictive layout or not. If it decides to do so, it will first
call #onLayoutChildren(Recycler, State)
with RecyclerView.State.isPreLayout()
set to
true
. At this stage, getWidth()
and getHeight()
will still
return the width and height of the RecyclerView as of the last layout calculation.
After handling the predictive case, RecyclerView will call
#onLayoutChildren(Recycler, State)
with RecyclerView.State.isMeasuring()
set to
true
and RecyclerView.State.isPreLayout()
set to false
. The LayoutManager can
access the measurement specs via getHeight()
, getHeightMode()
,
getWidth()
and getWidthMode()
.
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.#onLayoutChildren(Recycler, State)
with RecyclerView.State.isMeasuring()
set to
true
and RecyclerView.State.isPreLayout()
set to false
. RecyclerView will
take care of which views are actually added / removed / moved / changed for animations so
that the LayoutManager should not worry about them and handle each
#onLayoutChildren(Recycler, State)
call as if it is the last one.
RecyclerView.onLayout(boolean, int, int, int, int)
method is called, RecyclerView checks
whether it already did layout calculations during the measure pass and if so, it re-uses
that information. It may still decide to call #onLayoutChildren(Recycler, State)
if the last measure spec was different from the final dimensions or adapter contents
have changed between the measure call and the layout call.enabled
- True
if the Layout should be measured by the
RecyclerView, false
if the LayoutManager wants
to measure itself.setMeasuredDimension(Rect, int, int)
,
isAutoMeasureEnabled()
public boolean isAutoMeasureEnabled()
True
if the LayoutManager is measured by the RecyclerView or
false
if it measures itself.setAutoMeasureEnabled(boolean)
public boolean supportsPredictiveItemAnimations()
#onLayoutChildren(Recycler, State)
.
The default return value is false
, so subclasses of LayoutManager
will not get predictive item animations by default.
Whether item animations are enabled in a RecyclerView is determined both
by the return value from this method and the
ItemAnimator
set on the
RecyclerView itself. If the RecyclerView has a non-null ItemAnimator but this
method returns false, then simple item animations will be enabled, in which
views that are moving onto or off of the screen are simply faded in/out. If
the RecyclerView has a non-null ItemAnimator and this method returns true,
then there will be two calls to #onLayoutChildren(Recycler, State)
to
setup up the information needed to more intelligently predict where appearing
and disappearing views should be animated from/to.
public final void setItemPrefetchEnabled(boolean enabled)
If enabled, the LayoutManager will be queried for items to inflate/bind in between view system traversals on devices running API 21 or greater. Default value is true.
On platforms API level 21 and higher, the UI thread is idle between passing a frame to RenderThread and the starting up its next frame at the next VSync pulse. By prefetching out of window views in this time period, delays from inflation and view binding are much less likely to cause jank and stuttering during scrolls and flings.
While prefetch is enabled, it will have the side effect of expanding the effective size of the View cache to hold prefetched views.
enabled
- True
if items should be prefetched in between traversals.isItemPrefetchEnabled()
public final boolean isItemPrefetchEnabled()
setItemPrefetchEnabled(boolean)
public boolean isAttachedToWindow()
public void postOnAnimation(Runnable action)
Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
action
- The Runnable that will be executed.removeCallbacks(java.lang.Runnable)
public boolean removeCallbacks(Runnable action)
Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
action
- The Runnable to remove from the message handling queuepostOnAnimation(java.lang.Runnable)
@CallSuper public void onAttachedToWindow(RecyclerView view)
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.
view
- The RecyclerView this LayoutManager is bound to#onDetachedFromWindow(RecyclerView, Recycler)
@Deprecated public void onDetachedFromWindow(RecyclerView view)
#onDetachedFromWindow(RecyclerView, Recycler)
@CallSuper public void onDetachedFromWindow(RecyclerView view, RecyclerView.Recycler recycler)
LayoutManager should clear all of its View references as another LayoutManager might be assigned to the RecyclerView.
If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not
call #onLayoutChildren(Recycler, State)
if nothing has changed and a layout was
not requested on the RecyclerView while it was detached.
If your LayoutManager has View references that it cleans in on-detach, it should also
call RecyclerView.requestLayout()
to ensure that it is re-laid out when
RecyclerView is re-attached.
Subclass implementations should always call through to the superclass implementation.
view
- The RecyclerView this LayoutManager is bound torecycler
- The recycler to use if you prefer to recycle your children instead of
keeping them around.onAttachedToWindow(RecyclerView)
public boolean getClipToPadding()
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
ItemAnimator
, and simple
item animations are enabled. This means that add/remove operations on the
adapter will result in animations to add new or appearing items, removed or
disappearing items, and moved items. If a LayoutManager returns false from
supportsPredictiveItemAnimations()
, which is the default, and runs a
normal layout operation during #onLayoutChildren(Recycler, State)
, the
RecyclerView will have enough information to run those animations in a simple
way. For example, the default ItemAnimator, DefaultItemAnimator
, will
simply fade views in and out, whether they are actually added/removed or whether
they are moved on or off the screen due to other add/remove operations.
A LayoutManager wanting a better item animation experience, where items can be
animated onto and off of the screen according to where the items exist when they
are not on screen, then the LayoutManager should return true from
supportsPredictiveItemAnimations()
and add additional logic to
#onLayoutChildren(Recycler, State)
. Supporting predictive animations
means that #onLayoutChildren(Recycler, State)
will be called twice;
once as a "pre" layout step to determine where items would have been prior to
a real layout, and again to do the "real" layout. In the pre-layout phase,
items will remember their pre-layout positions to allow them to be laid out
appropriately. Also, removed
items will
be returned from the scrap to help determine correct placement of other items.
These removed items should not be added to the child list, but should be used
to help calculate correct positioning of other views, including views that
were not previously onscreen (referred to as APPEARING views), but whose
pre-layout offscreen position can be determined given the extra
information about the pre-layout removed views.
The second layout pass is the real layout in which only non-removed views
will be used. The only additional requirement during this pass is, if
supportsPredictiveItemAnimations()
returns true, to note which
views exist in the child list prior to layout and which are not there after
layout (referred to as DISAPPEARING views), and to position/layout those views
appropriately, without regard to the actual bounds of the RecyclerView. This allows
the animation system to know the location to which to animate these disappearing
views.
The default LayoutManager implementations for RecyclerView handle all of these requirements for animations already. Clients of RecyclerView can either use one of these layout managers directly or look at their implementations of onLayoutChildren() to see how they account for the APPEARING and DISAPPEARING views.
recycler
- Recycler to use for fetching potentially cached views for a
positionstate
- Transient state of RecyclerViewpublic void onLayoutCompleted(RecyclerView.State state)
#onLayoutChildren(Recycler, State)
calls due to animations or
layout measurement but it will include only one #onLayoutCompleted(State)
call.
This method will be called at the end of View.layout(int, int, int, int)
call.
This is a good place for the LayoutManager to do some cleanup like pending scroll position, saved state etc.
state
- Transient state of RecyclerViewpublic abstract RecyclerView.LayoutParams generateDefaultLayoutParams()
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
ViewGroup.checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
public boolean checkLayoutParams(RecyclerView.LayoutParams lp)
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.
lp
- LayoutParams object to checkpublic RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp)
Important: if you use your own custom LayoutParams
type
you must also override
ViewGroup.checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
lp
- Source LayoutParams object to copy values frompublic RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs)
Important: if you use your own custom LayoutParams
type
you must also override
ViewGroup.checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
c
- Context for obtaining styled attributesattrs
- AttributeSet describing the supplied argumentspublic int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state)
dx
- distance to scroll by in pixels. X increases as scroll position
approaches the right.recycler
- Recycler to use for fetching potentially cached views for a
positionstate
- Transient state of RecyclerViewMath.abs(result)
may be less than dx if a boundary was reached.public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state)
dy
- distance to scroll in pixels. Y increases as scroll position
approaches the bottom.recycler
- Recycler to use for fetching potentially cached views for a
positionstate
- Transient state of RecyclerViewMath.abs(result)
may be less than dy if a boundary was reached.public boolean canScrollHorizontally()
public boolean canScrollVertically()
public void scrollToPosition(int position)
position
- Scroll to this adapter position.public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position)
Smooth scroll to the specified adapter position.
To support smooth scrolling, override this method, create your RecyclerView.SmoothScroller
instance and call #startSmoothScroll(SmoothScroller)
.
recyclerView
- The RecyclerView to which this layout manager is attachedstate
- Current State of RecyclerViewposition
- Scroll to this adapter position.public void startSmoothScroll(RecyclerView.SmoothScroller smoothScroller)
Starts a smooth scroll using the provided SmoothScroller.
Calling this method will cancel any previous smooth scroll request.
smoothScroller
- Instance which defines how smooth scroll should be animatedpublic boolean isSmoothScrolling()
public int getLayoutDirection()
ViewCompat.LAYOUT_DIRECTION_RTL
if the layout
direction is RTL or returns
ViewCompat.LAYOUT_DIRECTION_LTR
if the layout direction
is not RTL.public void endAnimation(View view)
RecyclerView.ItemAnimator
.view
- The View for which the animations should be ended.RecyclerView.ItemAnimator.endAnimations()
public void addDisappearingView(View child)
#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.
child
- View to add and then remove with animation.public void addDisappearingView(View child, int index)
#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.
child
- View to add and then remove with animation.index
- Index of the view.public void addView(View child)
RecyclerView.Recycler
using
RecyclerView.Recycler.getViewForPosition(int)
.child
- View to addpublic void addView(View child, int index)
RecyclerView.Recycler
using
RecyclerView.Recycler.getViewForPosition(int)
.child
- View to addindex
- Index to add child atpublic void removeView(View child)
RecyclerView.Recycler.recycleView(android.view.View)
.child
- View to removepublic void removeViewAt(int index)
RecyclerView.Recycler.recycleView(android.view.View)
.index
- Index of the child view to removepublic void removeAllViews()
public int getBaseline()
public int getPosition(View view)
view
- The view to querypublic int getItemViewType(View view)
view
- The view to query@Nullable public View findContainingItemView(View view)
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).
view
- The view that is a descendant of the LayoutManager.RecyclerView.getChildViewHolder(View)
,
RecyclerView.findContainingViewHolder(View)
public View findViewByPosition(int 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.
position
- Position of the item in adapterpublic void detachView(View child)
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.
child
- Child to detachpublic void detachViewAt(int index)
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.
index
- Index of the child to detachpublic void attachView(View child, int index, RecyclerView.LayoutParams lp)
detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.child
- Child to reattachindex
- Intended child index for childlp
- LayoutParams for childpublic void attachView(View child, int index)
detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.child
- Child to reattachindex
- Intended child index for childpublic void attachView(View child)
detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.child
- Child to reattachpublic void removeDetachedView(View child)
detached
.child
- Detached child to removepublic void moveView(int fromIndex, int toIndex)
fromIndex
- The View's initial indextoIndex
- The View's target indexpublic void detachAndScrapView(View child, RecyclerView.Recycler recycler)
Recycler's
scrap heap.
Scrapping a view allows it to be rebound and reused to show updated or different data.
child
- Child to detach and scraprecycler
- Recycler to deposit the new scrap view intopublic void detachAndScrapViewAt(int index, RecyclerView.Recycler recycler)
Recycler's
scrap heap.
Scrapping a view allows it to be rebound and reused to show updated or different data.
index
- Index of child to detach and scraprecycler
- Recycler to deposit the new scrap view intopublic void removeAndRecycleView(View child, RecyclerView.Recycler recycler)
child
- Child to remove and recyclerecycler
- Recycler to use to recycle childpublic void removeAndRecycleViewAt(int index, RecyclerView.Recycler recycler)
index
- Index of child to remove and recyclerecycler
- Recycler to use to recycle childpublic int getChildCount()
public View getChildAt(int index)
index
- Index of child to returnpublic int getWidthMode()
This value is set only if the LayoutManager opts into the auto measure 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.
View.MeasureSpec#getMode(int)
,
View.onMeasure(int, int)
public int getHeightMode()
This value is set only if the LayoutManager opts into the auto measure 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.
View.MeasureSpec#getMode(int)
,
View.onMeasure(int, int)
public int getWidth()
public int getHeight()
public int getPaddingLeft()
public int getPaddingTop()
public int getPaddingRight()
public int getPaddingBottom()
public int getPaddingStart()
public int getPaddingEnd()
public boolean isFocused()
View.isFocused()
public boolean hasFocus()
View.hasFocus()
public View getFocusedChild()
public int getItemCount()
Note that this number is not necessarily equal to RecyclerView.State.getItemCount()
. In
methods where State is available, you should use RecyclerView.State.getItemCount()
instead.
For more details, check the documentation for RecyclerView.State.getItemCount()
.
RecyclerView.State.getItemCount()
public void offsetChildrenHorizontal(int dx)
dx
- Pixels to offset bypublic void offsetChildrenVertical(int dy)
dy
- Pixels to offset bypublic void ignoreView(View view)
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.
view
- View to ignore.stopIgnoringView(View)
public void stopIgnoringView(View view)
Note that calling this method removes all information in the view holder.
You can call this method only if your LayoutManger is in onLayout or onScroll callback.
view
- View to ignore.public void detachAndScrapAttachedViews(RecyclerView.Recycler recycler)
recycler
- Recycler to scrap views intopublic void measureChild(View child, int widthUsed, int heightUsed)
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.
child
- Child view to measurewidthUsed
- Width in pixels currently consumed by other views, if relevantheightUsed
- Height in pixels currently consumed by other views, if relevantpublic boolean isMeasurementCacheEnabled()
setMeasurementCacheEnabled(boolean)
.setMeasurementCacheEnabled(boolean)
public void setMeasurementCacheEnabled(boolean measurementCacheEnabled)
measurementCacheEnabled
- True to enable the measurement cache, false otherwise.isMeasurementCacheEnabled()
public void measureChildWithMargins(View child, int widthUsed, int heightUsed)
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.
child
- Child view to measurewidthUsed
- Width in pixels currently consumed by other views, if relevantheightUsed
- Height in pixels currently consumed by other views, if relevant@Deprecated public static int getChildMeasureSpec(int parentSize, int padding, int childDimension, boolean canScroll)
getChildMeasureSpec(int, int, int, int, boolean)
parentSize
- Size of the parent view where the child will be placedpadding
- Total space currently consumed by other elements of the parentchildDimension
- Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
Generally obtained from the child view's LayoutParamscanScroll
- true if the parent RecyclerView can scroll in this dimensionpublic static int getChildMeasureSpec(int parentSize, int parentMode, int padding, int childDimension, boolean canScroll)
parentSize
- Size of the parent view where the child will be placedparentMode
- The measurement spec mode of the parentpadding
- Total space currently consumed by other elements of parentchildDimension
- Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
Generally obtained from the child view's LayoutParamscanScroll
- true if the parent RecyclerView can scroll in this dimensionpublic int getDecoratedMeasuredWidth(View child)
ItemDecorations
.child
- Child view to queryItemDecoration
insetsView.getMeasuredWidth()
public int getDecoratedMeasuredHeight(View child)
ItemDecorations
.child
- Child view to queryItemDecoration
insetsView.getMeasuredHeight()
public void layoutDecorated(View child, int left, int top, int right, int bottom)
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)
child
- Child to lay outleft
- Left edge, with item decoration insets includedtop
- Top edge, with item decoration insets includedright
- Right edge, with item decoration insets includedbottom
- Bottom edge, with item decoration insets includedView.layout(int, int, int, int)
,
layoutDecoratedWithMargins(View, int, int, int, int)
public void layoutDecoratedWithMargins(View child, int left, int top, int right, int bottom)
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:
child
- Child to lay outleft
- Left edge, with item decoration insets and left margin includedtop
- Top edge, with item decoration insets and top margin includedright
- Right edge, with item decoration insets and right margin includedbottom
- Bottom edge, with item decoration insets and bottom margin includedView.layout(int, int, int, int)
,
layoutDecorated(View, int, int, int, int)
public void getTransformedBoundingBox(View child, boolean includeDecorInsets, Rect out)
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.
child
- The ItemView whose bounding box should be calculated.includeDecorInsets
- True if the decor insets should be included in the bounding boxout
- The rectangle into which the output will be written.public void getDecoratedBoundsWithMargins(View view, Rect outBounds)
view
- The view element to checkoutBounds
- A rect that will receive the bounds of the element including its
decoration and margins.public int getDecoratedLeft(View child)
ItemDecorations
.child
- Child to querygetLeftDecorationWidth(View)
public int getDecoratedTop(View child)
ItemDecorations
.child
- Child to querygetTopDecorationHeight(View)
public int getDecoratedRight(View child)
ItemDecorations
.child
- Child to querygetRightDecorationWidth(View)
public int getDecoratedBottom(View child)
ItemDecorations
.child
- Child to querygetBottomDecorationHeight(View)
public void calculateItemDecorationsForChild(View child, Rect outRect)
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.
child
- The child view whose decorations should be calculatedoutRect
- The Rect to hold result valuespublic int getTopDecorationHeight(View child)
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
child
- Child to querygetDecoratedTop(View)
,
calculateItemDecorationsForChild(View, Rect)
public int getBottomDecorationHeight(View child)
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
child
- Child to querygetDecoratedBottom(View)
,
calculateItemDecorationsForChild(View, Rect)
public int getLeftDecorationWidth(View child)
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
child
- Child to querygetDecoratedLeft(View)
,
calculateItemDecorationsForChild(View, Rect)
public int getRightDecorationWidth(View child)
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
child
- Child to querygetDecoratedRight(View)
,
calculateItemDecorationsForChild(View, Rect)
@Nullable public View onFocusSearchFailed(View focused, int direction, RecyclerView.Recycler recycler, RecyclerView.State state)
This is the LayoutManager's opportunity to populate views in the given direction to fulfill the request if it can. The LayoutManager should attach and return the view to be focused. The default implementation returns null.
focused
- The currently focused viewdirection
- One of View.FOCUS_UP
, View.FOCUS_DOWN
,
View.FOCUS_LEFT
, View.FOCUS_RIGHT
,
View.FOCUS_BACKWARD
, View.FOCUS_FORWARD
or 0 for not applicablerecycler
- The recycler to use for obtaining views for currently offscreen itemsstate
- Transient state of RecyclerViewpublic View onInterceptFocusSearch(View focused, int direction)
FocusFinder
is used. If this method returns
null FocusFinder will attempt to find a focusable child view. If it fails
then onFocusSearchFailed(View, int, RecyclerView.Recycler, RecyclerView.State)
will be called to give the LayoutManager an opportunity to add new views for items
that did not have attached views representing them. The LayoutManager should not add
or remove views from this method.focused
- The currently focused viewdirection
- One of View.FOCUS_UP
, View.FOCUS_DOWN
,
View.FOCUS_LEFT
, View.FOCUS_RIGHT
,
View.FOCUS_BACKWARD
, View.FOCUS_FORWARD
public boolean requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect, boolean immediate)
ViewParent.requestChildRectangleOnScreen(android.view.View,
android.graphics.Rect, boolean)
for more details.
The base implementation will attempt to perform a standard programmatic scroll to bring the given rect into view, within the padded area of the RecyclerView.
child
- The direct child making the request.rect
- The rectangle in the child's coordinates the child
wishes to be on the screen.immediate
- True to forbid animated or delayed scrolling,
false otherwise@Deprecated public boolean onRequestChildFocus(RecyclerView parent, View child, View focused)
#onRequestChildFocus(RecyclerView, State, View, View)
public boolean onRequestChildFocus(RecyclerView parent, RecyclerView.State state, View child, View focused)
A LayoutManager wishing to keep focused views aligned in a specific portion of the view may implement that behavior in an override of this method.
If the LayoutManager executes different behavior that should override the default behavior of scrolling the focused child on screen instead of running alongside it, this method should return true.
parent
- The RecyclerView hosting this LayoutManagerstate
- Current state of RecyclerViewchild
- Direct child of the RecyclerView containing the newly focused viewfocused
- The newly focused view. This may be the same view as child or it may be
nullpublic void onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter)
The default implementation removes all currently attached views.
oldAdapter
- The previous adapter instance. Will be null if there was previously no
adapter.newAdapter
- The new adapter instance. Might be null if
RecyclerView.setAdapter(RecyclerView.Adapter)
is called with null
.public boolean onAddFocusables(RecyclerView recyclerView, ArrayList<View> views, int direction, int focusableMode)
The LayoutManager implementation should return true
if the default
behavior of View.addFocusables(java.util.ArrayList, int)
should be
suppressed.
The default implementation returns false
to trigger RecyclerView
to fall back to the default ViewGroup behavior.
recyclerView
- The RecyclerView hosting this LayoutManagerviews
- List of output views. This method should add valid focusable views
to this list.direction
- One of View.FOCUS_UP
, View.FOCUS_DOWN
,
View.FOCUS_LEFT
, View.FOCUS_RIGHT
,
View.FOCUS_BACKWARD
, View.FOCUS_FORWARD
focusableMode
- The type of focusables to be added.View.FOCUSABLES_ALL
,
View.FOCUSABLES_TOUCH_MODE
public void onItemsChanged(RecyclerView recyclerView)
RecyclerView.Adapter.notifyDataSetChanged()
is triggered instead of giving
detailed information on what has actually changed.recyclerView
- public void onItemsAdded(RecyclerView recyclerView, int positionStart, int itemCount)
recyclerView
- positionStart
- itemCount
- public void onItemsRemoved(RecyclerView recyclerView, int positionStart, int itemCount)
recyclerView
- positionStart
- itemCount
- public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount)
onItemsUpdated(RecyclerView, int, int, Object)
instead, then this callback will not be invoked.recyclerView
- positionStart
- itemCount
- public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount, Object payload)
onItemsUpdated(RecyclerView, int, int)
.recyclerView
- positionStart
- itemCount
- payload
- public void onItemsMoved(RecyclerView recyclerView, int from, int to, int itemCount)
Note that, an item may also change position in response to another ADD/REMOVE/MOVE
operation. This callback is only called if and only if RecyclerView.Adapter.notifyItemMoved(int, int)
is called.
recyclerView
- from
- to
- itemCount
- public int computeHorizontalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeHorizontalScrollExtent()
for details.
Default implementation returns 0.
state
- Current state of RecyclerViewRecyclerView.computeHorizontalScrollExtent()
public int computeHorizontalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeHorizontalScrollOffset()
for details.
Default implementation returns 0.
state
- Current State of RecyclerView where you can find total item countRecyclerView.computeHorizontalScrollOffset()
public int computeHorizontalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeHorizontalScrollRange()
for details.
Default implementation returns 0.
state
- Current State of RecyclerView where you can find total item countRecyclerView.computeHorizontalScrollRange()
public int computeVerticalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeVerticalScrollExtent()
for details.
Default implementation returns 0.
state
- Current state of RecyclerViewRecyclerView.computeVerticalScrollExtent()
public int computeVerticalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeVerticalScrollOffset()
for details.
Default implementation returns 0.
state
- Current State of RecyclerView where you can find total item countRecyclerView.computeVerticalScrollOffset()
public int computeVerticalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars.
Read RecyclerView.computeVerticalScrollRange()
for details.
Default implementation returns 0.
state
- Current State of RecyclerView where you can find total item countRecyclerView.computeVerticalScrollRange()
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec)
setMeasuredDimension(int, int)
before returning.
The default implementation will handle EXACTLY measurements and respect the minimum width and height properties of the host RecyclerView if measured as UNSPECIFIED. AT_MOST measurements will be treated as EXACTLY and the RecyclerView will consume all available space.
recycler
- Recyclerstate
- Transient state of RecyclerViewwidthSpec
- Width View.MeasureSpec
heightSpec
- Height View.MeasureSpec
public void setMeasuredDimension(int widthSize, int heightSize)
Set the measured dimensions
of the
host RecyclerView.widthSize
- Measured widthheightSize
- Measured heightpublic int getMinimumWidth()
View.getMinimumWidth()
public int getMinimumHeight()
View.getMinimumHeight()
public Parcelable onSaveInstanceState()
Called when the LayoutManager should save its state. This is a good time to save your scroll position, configuration and anything else that may be required to restore the same layout state if the LayoutManager is recreated.
RecyclerView does NOT verify if the LayoutManager has changed between state save and restore. This will let you share information between your LayoutManagers but it is also your responsibility to make sure they use the same parcelable class.
public void onRestoreInstanceState(Parcelable state)
public void onScrollStateChanged(int state)
state
- The new scroll state for RecyclerViewpublic void removeAndRecycleAllViews(RecyclerView.Recycler recycler)
If you want to clean cached views as well, you should call RecyclerView.Recycler.clear()
too.
If a View is marked as "ignored", it is not removed nor recycled.
recycler
- Recycler to use to recycle children#removeAndRecycleView(View, Recycler)
,
#removeAndRecycleViewAt(int, Recycler)
,
ignoreView(View)
public void onInitializeAccessibilityNodeInfo(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityNodeInfoCompat info)
Default implementation adds a AccessibilityNodeInfoCompat.CollectionInfoCompat
.
You should override
getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)
and
getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)
for
more accurate accessibility information.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewinfo
- The info that should be filled by the LayoutManagerView.onInitializeAccessibilityNodeInfo(
android.view.accessibility.AccessibilityNodeInfo)
,
getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)
,
getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)
public void onInitializeAccessibilityEvent(AccessibilityEvent event)
public void onInitializeAccessibilityEvent(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityEvent event)
Default implementation adds item count and scroll information to the event.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewevent
- The event instance to initializeView.onInitializeAccessibilityEvent(android.view.accessibility.AccessibilityEvent)
public void onInitializeAccessibilityNodeInfoForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View host, AccessibilityNodeInfoCompat info)
Default implementation adds basic positioning information about the item.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewhost
- The child for which accessibility node info should be populatedinfo
- The info to fill out about the itemAbsListView.onInitializeAccessibilityNodeInfoForItem(View, int,
android.view.accessibility.AccessibilityNodeInfo)
public void requestSimpleAnimationsInNextLayout()
Note that, calling this method will not guarantee that RecyclerView will run animations
at all. For example, if there is not any RecyclerView.ItemAnimator
set, RecyclerView will
not run any animations but will still clear this flag after the layout is complete.
public int getSelectionModeForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
AccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_NONE
,
AccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_SINGLE
or
AccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_MULTIPLE
.
Default implementation returns
AccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_NONE
.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewAccessibilityNodeInfoCompat.CollectionInfoCompat#SELECTION_MODE_NONE
.public int getRowCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Default implementation returns the number of items in the adapter if LayoutManager supports vertical scrolling or 1 if LayoutManager does not support vertical scrolling.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewpublic int getColumnCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Default implementation returns the number of items in the adapter if LayoutManager supports horizontal scrolling or 1 if LayoutManager does not support horizontal scrolling.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewpublic boolean isLayoutHierarchical(RecyclerView.Recycler recycler, RecyclerView.State state)
Default implementation returns false.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewpublic boolean performAccessibilityAction(RecyclerView.Recycler recycler, RecyclerView.State state, int action, Bundle args)
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewaction
- The action to performargs
- Optional action argumentsView.performAccessibilityAction(int, android.os.Bundle)
public boolean performAccessibilityActionForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View view, int action, Bundle args)
Default implementation does not do anything.
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewview
- The child view on which the action is performedaction
- The action to performargs
- Optional action argumentsView.performAccessibilityAction(int, android.os.Bundle)
public static RecyclerView.LayoutManager.Properties getProperties(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)