public class GridLayoutManager extends LinearLayoutManager
RecyclerView.LayoutManager
implementations that lays out items in a grid.
By default, each item occupies 1 span. You can change it by providing a custom
GridLayoutManager.SpanSizeLookup
instance via setSpanSizeLookup(SpanSizeLookup)
.
Modifier and Type | Class and Description |
---|---|
static class |
GridLayoutManager.DefaultSpanSizeLookup
Default implementation for
GridLayoutManager.SpanSizeLookup . |
static class |
GridLayoutManager.LayoutParams
LayoutParams used by GridLayoutManager.
|
static class |
GridLayoutManager.SpanSizeLookup
A helper class to provide the number of spans each item occupies.
|
LinearLayoutManager.LayoutChunkResult, LinearLayoutManager.SavedState
RecyclerView.LayoutManager.Properties
Modifier and Type | Field and Description |
---|---|
static int |
DEFAULT_SPAN_COUNT |
HORIZONTAL, INVALID_OFFSET, VERTICAL
Constructor and Description |
---|
GridLayoutManager(Context context,
AttributeSet attrs,
int defStyleAttr,
int defStyleRes)
Constructor used when layout manager is set in XML by RecyclerView attribute
"layoutManager".
|
GridLayoutManager(Context context,
int spanCount)
Creates a vertical GridLayoutManager
|
GridLayoutManager(Context context,
int spanCount,
int orientation,
boolean reverseLayout) |
Modifier and Type | Method and Description |
---|---|
boolean |
checkLayoutParams(RecyclerView.LayoutParams lp)
Determines the validity of the supplied LayoutParams object.
|
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 |
getColumnCountForAccessibility(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns the number of columns for accessibility.
|
int |
getRowCountForAccessibility(RecyclerView.Recycler recycler,
RecyclerView.State state)
Returns the number of rows for accessibility.
|
int |
getSpanCount()
Returns the number of spans laid out by this grid.
|
GridLayoutManager.SpanSizeLookup |
getSpanSizeLookup()
Returns the current
GridLayoutManager.SpanSizeLookup used by the GridLayoutManager. |
View |
onFocusSearchFailed(View focused,
int focusDirection,
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 |
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.
|
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,
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.
|
int |
scrollHorizontallyBy(int dx,
RecyclerView.Recycler recycler,
RecyclerView.State state)
Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.
|
int |
scrollVerticallyBy(int dy,
RecyclerView.Recycler recycler,
RecyclerView.State state)
Scroll vertically by dy pixels in screen coordinates and return the distance traveled.
|
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 |
setSpanCount(int spanCount)
Sets the number of spans to be laid out.
|
void |
setSpanSizeLookup(GridLayoutManager.SpanSizeLookup spanSizeLookup)
Sets the source to get the number of spans occupied by each item in the adapter.
|
void |
setStackFromEnd(boolean stackFromEnd)
stackFromEnd is not supported by GridLayoutManager.
|
boolean |
supportsPredictiveItemAnimations()
Returns whether this LayoutManager supports automatic item animations.
|
assertNotInLayoutOrScroll, canScrollHorizontally, canScrollVertically, computeHorizontalScrollExtent, computeHorizontalScrollOffset, computeHorizontalScrollRange, computeScrollVectorForPosition, computeVerticalScrollExtent, computeVerticalScrollOffset, computeVerticalScrollRange, findFirstCompletelyVisibleItemPosition, findFirstVisibleItemPosition, findLastCompletelyVisibleItemPosition, findLastVisibleItemPosition, findViewByPosition, getExtraLayoutSpace, getOrientation, getRecycleChildrenOnDetach, getReverseLayout, getStackFromEnd, isLayoutRTL, isSmoothScrollbarEnabled, onDetachedFromWindow, onInitializeAccessibilityEvent, onRestoreInstanceState, onSaveInstanceState, prepareForDrop, scrollToPosition, scrollToPositionWithOffset, setOrientation, setRecycleChildrenOnDetach, setReverseLayout, setSmoothScrollbarEnabled, smoothScrollToPosition
addDisappearingView, addDisappearingView, addView, addView, assertInLayoutOrScroll, attachView, attachView, attachView, calculateItemDecorationsForChild, chooseSize, detachAndScrapAttachedViews, detachAndScrapView, detachAndScrapViewAt, detachView, detachViewAt, endAnimation, findContainingItemView, getBaseline, getBottomDecorationHeight, getChildAt, getChildCount, getChildMeasureSpec, getChildMeasureSpec, getClipToPadding, getDecoratedBottom, getDecoratedBoundsWithMargins, getDecoratedLeft, getDecoratedMeasuredHeight, getDecoratedMeasuredWidth, getDecoratedRight, getDecoratedTop, getFocusedChild, getHeight, getHeightMode, getItemCount, getItemViewType, getLayoutDirection, getLeftDecorationWidth, getMinimumHeight, getMinimumWidth, getPaddingBottom, getPaddingEnd, getPaddingLeft, getPaddingRight, getPaddingStart, getPaddingTop, getPosition, getProperties, getRightDecorationWidth, getSelectionModeForAccessibility, getTopDecorationHeight, getTransformedBoundingBox, getWidth, getWidthMode, hasFocus, ignoreView, isAttachedToWindow, isAutoMeasureEnabled, isFocused, isItemPrefetchEnabled, isLayoutHierarchical, isMeasurementCacheEnabled, isSmoothScrolling, layoutDecorated, layoutDecoratedWithMargins, measureChild, measureChildWithMargins, moveView, offsetChildrenHorizontal, offsetChildrenVertical, onAdapterChanged, onAddFocusables, onAttachedToWindow, onDetachedFromWindow, onInitializeAccessibilityEvent, onInitializeAccessibilityNodeInfo, onInterceptFocusSearch, onItemsUpdated, onMeasure, onRequestChildFocus, onRequestChildFocus, onScrollStateChanged, performAccessibilityAction, performAccessibilityActionForItem, postOnAnimation, removeAllViews, removeAndRecycleAllViews, removeAndRecycleView, removeAndRecycleViewAt, removeCallbacks, removeDetachedView, removeView, removeViewAt, requestChildRectangleOnScreen, requestLayout, requestSimpleAnimationsInNextLayout, setAutoMeasureEnabled, setItemPrefetchEnabled, setMeasuredDimension, setMeasurementCacheEnabled, startSmoothScroll, stopIgnoringView
public static final int DEFAULT_SPAN_COUNT
public GridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
public GridLayoutManager(Context context, int spanCount)
context
- Current context, will be used to access resources.spanCount
- The number of columns in the gridpublic GridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout)
context
- Current context, will be used to access resources.spanCount
- The number of columns or rows in the gridorientation
- Layout orientation. Should be LinearLayoutManager.HORIZONTAL
or LinearLayoutManager.VERTICAL
.reverseLayout
- When set to true, layouts from end to start.public void setStackFromEnd(boolean stackFromEnd)
LinearLayoutManager.setReverseLayout(boolean)
.setStackFromEnd
in class LinearLayoutManager
public int getRowCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
RecyclerView.LayoutManager
Default implementation returns the number of items in the adapter if LayoutManager supports vertical scrolling or 1 if LayoutManager does not support vertical scrolling.
getRowCountForAccessibility
in class RecyclerView.LayoutManager
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)
RecyclerView.LayoutManager
Default implementation returns the number of items in the adapter if LayoutManager supports horizontal scrolling or 1 if LayoutManager does not support horizontal scrolling.
getColumnCountForAccessibility
in class RecyclerView.LayoutManager
recycler
- The Recycler that can be used to convert view positions into adapter
positionsstate
- The current state of RecyclerViewpublic void onInitializeAccessibilityNodeInfoForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View host, AccessibilityNodeInfoCompat info)
RecyclerView.LayoutManager
Default implementation adds basic positioning information about the item.
onInitializeAccessibilityNodeInfoForItem
in class RecyclerView.LayoutManager
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 onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
LinearLayoutManager
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
RecyclerView.LayoutManager.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
RecyclerView.LayoutManager.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
RecyclerView.LayoutManager.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.
onLayoutChildren
in class LinearLayoutManager
recycler
- Recycler to use for fetching potentially cached views for a
positionstate
- Transient state of RecyclerViewpublic void onLayoutCompleted(RecyclerView.State state)
RecyclerView.LayoutManager
#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.
onLayoutCompleted
in class LinearLayoutManager
state
- Transient state of RecyclerViewpublic void onItemsAdded(RecyclerView recyclerView, int positionStart, int itemCount)
RecyclerView.LayoutManager
onItemsAdded
in class RecyclerView.LayoutManager
public void onItemsChanged(RecyclerView recyclerView)
RecyclerView.LayoutManager
RecyclerView.Adapter.notifyDataSetChanged()
is triggered instead of giving
detailed information on what has actually changed.onItemsChanged
in class RecyclerView.LayoutManager
public void onItemsRemoved(RecyclerView recyclerView, int positionStart, int itemCount)
RecyclerView.LayoutManager
onItemsRemoved
in class RecyclerView.LayoutManager
public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount, Object payload)
RecyclerView.LayoutManager
RecyclerView.LayoutManager.onItemsUpdated(RecyclerView, int, int)
.onItemsUpdated
in class RecyclerView.LayoutManager
public void onItemsMoved(RecyclerView recyclerView, int from, int to, int itemCount)
RecyclerView.LayoutManager
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.
onItemsMoved
in class RecyclerView.LayoutManager
public RecyclerView.LayoutParams generateDefaultLayoutParams()
LinearLayoutManager
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)
,
RecyclerView.LayoutManager.generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
RecyclerView.LayoutManager.generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
generateDefaultLayoutParams
in class LinearLayoutManager
public RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs)
RecyclerView.LayoutManager
Important: if you use your own custom LayoutParams
type
you must also override
ViewGroup.checkLayoutParams(LayoutParams)
,
RecyclerView.LayoutManager.generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
RecyclerView.LayoutManager.generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
generateLayoutParams
in class RecyclerView.LayoutManager
c
- Context for obtaining styled attributesattrs
- AttributeSet describing the supplied argumentspublic RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp)
RecyclerView.LayoutManager
Important: if you use your own custom LayoutParams
type
you must also override
ViewGroup.checkLayoutParams(LayoutParams)
,
RecyclerView.LayoutManager.generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
RecyclerView.LayoutManager.generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
generateLayoutParams
in class RecyclerView.LayoutManager
lp
- Source LayoutParams object to copy values frompublic boolean checkLayoutParams(RecyclerView.LayoutParams lp)
RecyclerView.LayoutManager
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.
checkLayoutParams
in class RecyclerView.LayoutManager
lp
- LayoutParams object to checkpublic void setSpanSizeLookup(GridLayoutManager.SpanSizeLookup spanSizeLookup)
spanSizeLookup
- GridLayoutManager.SpanSizeLookup
instance to be used to query number of spans
occupied by each itempublic GridLayoutManager.SpanSizeLookup getSpanSizeLookup()
GridLayoutManager.SpanSizeLookup
used by the GridLayoutManager.GridLayoutManager.SpanSizeLookup
used by the GridLayoutManager.public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)
RecyclerView.LayoutManager
RecyclerView.onMeasure(int, int)
. It is
called after the RecyclerView calls
LayoutManager#onLayoutChildren(Recycler, State)
during a measurement pass.
This method should call RecyclerView.LayoutManager.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.
setMeasuredDimension
in class RecyclerView.LayoutManager
childrenBounds
- The bounding box of all childrenwSpec
- The widthMeasureSpec that was passed into the RecyclerView.hSpec
- The heightMeasureSpec that was passed into the RecyclerView.RecyclerView.LayoutManager.setAutoMeasureEnabled(boolean)
public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state)
LinearLayoutManager
scrollHorizontallyBy
in class LinearLayoutManager
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)
LinearLayoutManager
scrollVerticallyBy
in class LinearLayoutManager
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 int getSpanCount()
setSpanCount(int)
public void setSpanCount(int spanCount)
If LinearLayoutManager.getOrientation()
is LinearLayoutManager.VERTICAL
, this is the number of columns.
If LinearLayoutManager.getOrientation()
is LinearLayoutManager.HORIZONTAL
, this is the number of rows.
spanCount
- The total number of spans in the gridgetSpanCount()
public View onFocusSearchFailed(View focused, int focusDirection, RecyclerView.Recycler recycler, RecyclerView.State state)
RecyclerView.LayoutManager
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.
onFocusSearchFailed
in class LinearLayoutManager
focused
- The currently focused viewfocusDirection
- 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 boolean supportsPredictiveItemAnimations()
RecyclerView.LayoutManager
#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.
supportsPredictiveItemAnimations
in class LinearLayoutManager