com.azoft.carousellayoutmanager

Class CarouselLayoutManager

java.lang.Object

RecyclerView.LayoutManager

com.azoft.carousellayoutmanager.CarouselLayoutManager

public class CarouselLayoutManager
extends RecyclerView.LayoutManager

An implementation of RecyclerView.LayoutManager that layout items like carousel. Generally there is one center item and bellow this item there are maximum getMaxVisibleItems() items on each side of the center item. By default getMaxVisibleItems() is MAX_VISIBLE_ITEMS.

This LayoutManager supports only fixedSized adapter items.

This LayoutManager supports HORIZONTAL and VERTICAL orientations.

This LayoutManager supports circle layout. By default it if disabled. We don't recommend to use circle layout with adapter items count less then 3.

Please be sure that layout_width of adapter item is a constant value and not ViewGroup.LayoutParams#MATCH_PARENT for HORIZONTAL orientation. So like layout_height is not ViewGroup.LayoutParams#MATCH_PARENT for VERTICAL

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	CarouselLayoutManager.CarouselSavedState
static interface	CarouselLayoutManager.OnCenterItemSelectionListener
static interface	CarouselLayoutManager.PostLayoutListener This interface methods will be called for each visible view item after general LayoutManager layout finishes.

Field Summary

Fields

Modifier and Type	Field and Description
static int	HORIZONTAL
static int	INVALID_POSITION
static int	MAX_VISIBLE_ITEMS
static int	VERTICAL

Constructor Summary

Constructors

Constructor and Description
CarouselLayoutManager(int orientation)
CarouselLayoutManager(int orientation, boolean circleLayout) If circleLayout is true then all items will be in cycle.

Method Summary

Modifier and Type	Method and Description
void	addOnItemSelectionListener(CarouselLayoutManager.OnCenterItemSelectionListener onCenterItemSelectionListener)
boolean	canScrollHorizontally()
boolean	canScrollVertically()
android.graphics.PointF	computeScrollVectorForPosition(int targetPosition)
protected double	convertItemPositionDiffToSmoothPositionDiff(float itemPositionDiff) Called during getCardOffsetByPositionDiff(float) for better item movement.
RecyclerView.LayoutParams	generateDefaultLayoutParams()
protected int	getCardOffsetByPositionDiff(float itemPositionDiff) Called during fillData(RecyclerView.Recycler, RecyclerView.State) to calculate item offset from layout center line.
int	getCenterItemPosition()
int	getHeightNoPadding()
int	getMaxVisibleItems()
protected int	getOffsetCenterView()
protected int	getOffsetForCurrentView(android.view.View view)
int	getOrientation()
protected int	getScrollItemSize()
int	getWidthNoPadding()
void	onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter)
void	onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
void	onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec)
void	onRestoreInstanceState(android.os.Parcelable state)
android.os.Parcelable	onSaveInstanceState()
void	removeOnItemSelectionListener(CarouselLayoutManager.OnCenterItemSelectionListener onCenterItemSelectionListener)
protected int	scrollBy(int diff, RecyclerView.Recycler recycler, RecyclerView.State state) This method is called from scrollHorizontallyBy(int, RecyclerView.Recycler, RecyclerView.State) and scrollVerticallyBy(int, RecyclerView.Recycler, RecyclerView.State) to calculate needed scroll that is allowed.
int	scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state)
void	scrollToPosition(int position)
int	scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state)
void	setMaxVisibleItems(int maxVisibleItems) Setup maximum visible (layout) items on each side of the center item.
void	setPostLayoutListener(CarouselLayoutManager.PostLayoutListener postLayoutListener) Setup CarouselLayoutManager.PostLayoutListener for this LayoutManager.
void	smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

HORIZONTAL

public static final int HORIZONTAL

VERTICAL

public static final int VERTICAL

INVALID_POSITION

public static final int INVALID_POSITION

See Also:

Constant Field Values

MAX_VISIBLE_ITEMS

public static final int MAX_VISIBLE_ITEMS

See Also:

Constant Field Values

Constructor Detail

CarouselLayoutManager

public CarouselLayoutManager(int orientation)

Parameters:

orientation - should be VERTICAL or HORIZONTAL

CarouselLayoutManager

public CarouselLayoutManager(int orientation,
                             boolean circleLayout)

If circleLayout is true then all items will be in cycle. Scroll will be infinite on both sides.

Parameters:

orientation - should be VERTICAL or HORIZONTAL

circleLayout - true for enabling circleLayout

Method Detail

setPostLayoutListener

public void setPostLayoutListener(CarouselLayoutManager.PostLayoutListener postLayoutListener)

Setup CarouselLayoutManager.PostLayoutListener for this LayoutManager. Its methods will be called for each visible view item after general LayoutManager layout finishes.

Generally this method should be used for scaling and translating view item for better (different) view presentation of layouting.

Parameters:

postLayoutListener - listener for item layout changes. Can be null.

setMaxVisibleItems

public void setMaxVisibleItems(int maxVisibleItems)

Setup maximum visible (layout) items on each side of the center item. Basically during scrolling there can be more visible items (+1 item on each side), but in idle state this is the only reached maximum.

Parameters:

maxVisibleItems - should be great then 0, if bot an IllegalAccessException will be thrown

getMaxVisibleItems

public int getMaxVisibleItems()

Returns:

current setup for maximum visible items.

See Also:

setMaxVisibleItems(int)

generateDefaultLayoutParams

public RecyclerView.LayoutParams generateDefaultLayoutParams()

getOrientation

public int getOrientation()

Returns:

current layout orientation

See Also:

VERTICAL, HORIZONTAL

canScrollHorizontally

public boolean canScrollHorizontally()

canScrollVertically

public boolean canScrollVertically()

getCenterItemPosition

public int getCenterItemPosition()

Returns:

current layout center item

addOnItemSelectionListener

public void addOnItemSelectionListener(CarouselLayoutManager.OnCenterItemSelectionListener onCenterItemSelectionListener)

Parameters:

onCenterItemSelectionListener - listener that will trigger when ItemSelectionChanges. can't be null

removeOnItemSelectionListener

public void removeOnItemSelectionListener(CarouselLayoutManager.OnCenterItemSelectionListener onCenterItemSelectionListener)

Parameters:

onCenterItemSelectionListener - listener that was previously added by addOnItemSelectionListener(OnCenterItemSelectionListener)

scrollToPosition

public void scrollToPosition(int position)

smoothScrollToPosition

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

computeScrollVectorForPosition

public android.graphics.PointF computeScrollVectorForPosition(int targetPosition)

scrollVerticallyBy

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

scrollHorizontallyBy

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

scrollBy

protected int scrollBy(int diff,
                       RecyclerView.Recycler recycler,
                       RecyclerView.State state)

This method is called from scrollHorizontallyBy(int, RecyclerView.Recycler, RecyclerView.State) and scrollVerticallyBy(int, RecyclerView.Recycler, RecyclerView.State) to calculate needed scroll that is allowed.

This method may do relayout work.

Parameters:

diff - distance that we want to scroll by

recycler - Recycler to use for fetching potentially cached views for a position

state - Transient state of RecyclerView

Returns:

distance that we actually scrolled by

onMeasure

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

onAdapterChanged

public void onAdapterChanged(RecyclerView.Adapter oldAdapter,
                             RecyclerView.Adapter newAdapter)

onLayoutChildren

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

getWidthNoPadding

public int getWidthNoPadding()

getHeightNoPadding

public int getHeightNoPadding()

getCardOffsetByPositionDiff

protected int getCardOffsetByPositionDiff(float itemPositionDiff)

Called during fillData(RecyclerView.Recycler, RecyclerView.State) to calculate item offset from layout center line.

Returns convertItemPositionDiffToSmoothPositionDiff(float) * (size off area above center item when it is on the center).
Sign is: plus if this item is bellow center line, minus if not

----- - area above it
||||| - center item
----- - area bellow it (it has the same size as are above center item)

Parameters:

itemPositionDiff - current item difference with layout center line. if this is 0, then this item center is in layout center line. if this is 1 then this item is bellow the layout center line in the full item size distance.

Returns:

offset in scroll px coordinates.

convertItemPositionDiffToSmoothPositionDiff

protected double convertItemPositionDiffToSmoothPositionDiff(float itemPositionDiff)

Called during getCardOffsetByPositionDiff(float) for better item movement.
Current implementation speed up items that are far from layout center line and slow down items that are close to this line. This code is full of maths. If you want to make items move in a different way, probably you should override this method.
Please see code comments for better explanations.

Parameters:

itemPositionDiff - current item difference with layout center line. if this is 0, then this item center is in layout center line. if this is 1 then this item is bellow the layout center line in the full item size distance.

Returns:

smooth position offset. needed for scroll calculation and better user experience.

See Also:

getCardOffsetByPositionDiff(float)

getScrollItemSize

protected int getScrollItemSize()

Returns:

full item size

onSaveInstanceState

public android.os.Parcelable onSaveInstanceState()

onRestoreInstanceState

public void onRestoreInstanceState(android.os.Parcelable state)

getOffsetCenterView

protected int getOffsetCenterView()

Returns:

Scroll offset from nearest item from center

getOffsetForCurrentView

protected int getOffsetForCurrentView(android.view.View view)