Method Detail

• onStartNestedScroll

   abstract boolean onStartNestedScroll(@NonNull() View child, @NonNull() View target, int axes)

  React to a descendant view initiating a nestable scroll operation, claiming thenested scroll operation if appropriate.

  This method will be called in response to a descendant view invoking startNestedScroll. Each parent up the view hierarchy will begiven an opportunity to respond and claim the nested scrolling operation by returningtrue.

  This method may be overridden by ViewParent implementations to indicate when the viewis willing to support a nested scrolling operation that is about to begin. If it returnstrue, this ViewParent will become the target view's nested scrolling parent for the durationof the scroll operation in progress. When the nested scroll is finished this ViewParentwill receive a call to onStopNestedScroll.

  Parameters:

  child - Direct child of this ViewParent containing target

  target - View that initiated the nested scroll

  axes - Flags consisting of SCROLL_AXIS_HORIZONTAL,SCROLL_AXIS_VERTICAL or both

• onNestedScrollAccepted

   abstract void onNestedScrollAccepted(@NonNull() View child, @NonNull() View target, int axes)

  React to the successful claiming of a nested scroll operation.

  This method will be called after onStartNestedScroll returns true. It offersan opportunity for the view and its superclasses to perform initial configurationfor the nested scroll. Implementations of this method should always call their superclass'simplementation of this method if one is present.

  Parameters:

  child - Direct child of this ViewParent containing target

  target - View that initiated the nested scroll

  axes - Flags consisting of SCROLL_AXIS_HORIZONTAL,SCROLL_AXIS_VERTICAL or both

• onStopNestedScroll

   abstract void onStopNestedScroll(@NonNull() View target)

  React to a nested scroll operation ending.

  Perform cleanup after a nested scrolling operation.This method will be called when a nested scroll stops, for example when a nested touchscroll ends with a ACTION_UP or ACTION_CANCEL event.Implementations of this method should always call their superclass's implementation of thismethod if one is present.

  Parameters:

  target - View that initiated the nested scroll

• onNestedScroll

   abstract void onNestedScroll(@NonNull() View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed)

  React to a nested scroll in progress.

  This method will be called when the ViewParent's current nested scrolling child viewdispatches a nested scroll event. To receive calls to this method the ViewParent must havepreviously returned true for a call to onStartNestedScroll.

  Both the consumed and unconsumed portions of the scroll distance are reported to theViewParent. An implementation may choose to use the consumed portion to match or chase scrollposition of multiple child elements, for example. The unconsumed portion may be used toallow continuous dragging of multiple scrolling or draggable elements, such as scrollinga list within a vertical drawer where the drawer begins dragging once the edge of innerscrolling content is reached.

  Parameters:

  target - The descendent view controlling the nested scroll

  dxConsumed - Horizontal scroll distance in pixels already consumed by target

  dyConsumed - Vertical scroll distance in pixels already consumed by target

  dxUnconsumed - Horizontal scroll distance in pixels not consumed by target

  dyUnconsumed - Vertical scroll distance in pixels not consumed by target

• onNestedPreScroll

   abstract void onNestedPreScroll(@NonNull() View target, int dx, int dy, @NonNull() Array<int> consumed)

  React to a nested scroll in progress before the target view consumes a portion of the scroll.

  When working with nested scrolling often the parent view may want an opportunityto consume the scroll before the nested scrolling child does. An example of this is adrawer that contains a scrollable list. The user will want to be able to scroll the listfully into view before the list itself begins scrolling.

  onNestedPreScroll is called when a nested scrolling child invokes dispatchNestedPreScroll. The implementation shouldreport how any pixels of the scroll reported by dx, dy were consumed in theconsumed array. Index 0 corresponds to dx and index 1 corresponds to dy.This parameter will never be null. Initial values for consumed[0] and consumed[1]will always be 0.

  Parameters:

  target - View that initiated the nested scroll

  dx - Horizontal scroll distance in pixels

  dy - Vertical scroll distance in pixels

  consumed - Output.

• onNestedFling

   abstract boolean onNestedFling(@NonNull() View target, float velocityX, float velocityY, boolean consumed)

  Request a fling from a nested scroll.

  This method signifies that a nested scrolling child has detected suitable conditionsfor a fling. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceedsthe minimum fling velocity along a scrollable axis.

  If a nested scrolling child view would normally fling but it is at the edge ofits own content, it can use this method to delegate the fling to its nested scrollingparent instead. The parent may optionally consume the fling or observe a child fling.

  Parameters:

  target - View that initiated the nested scroll

  velocityX - Horizontal velocity in pixels per second

  velocityY - Vertical velocity in pixels per second

  consumed - true if the child consumed the fling, false otherwise

• onNestedPreFling

   abstract boolean onNestedPreFling(@NonNull() View target, float velocityX, float velocityY)

  React to a nested fling before the target view consumes it.

  This method siginfies that a nested scrolling child has detected a fling with the givenvelocity along each axis. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceedsthe minimum fling velocity along a scrollable axis.

  If a nested scrolling parent is consuming motion as part of a pre-scroll, it may be appropriate forit to also consume the pre-fling to complete that same motion. By returningtrue from this method, the parent indicates that the child should notfling its own internal content as well.

  Parameters:

  target - View that initiated the nested scroll

  velocityX - Horizontal velocity in pixels per second

  velocityY - Vertical velocity in pixels per second

• getNestedScrollAxes

   abstract int getNestedScrollAxes()

  Return the current axes of nested scrolling for this NestedScrollingParent.

  A NestedScrollingParent returning something other than SCROLL_AXIS_NONE is currently acting as a nested scrolling parent for one or more descendant views inthe hierarchy.