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added in version 26.1.0
belongs to Maven artifact com.android.support:support-compat:28.0.0-alpha1

NestedScrollingParent2

public interface NestedScrollingParent2
implements NestedScrollingParent

android.support.v4.view.NestedScrollingParent2
Known Indirect Subclasses


This interface should be implemented by ViewGroup subclasses that wish to support scrolling operations delegated by a nested child view.

Classes implementing this interface should create a final instance of a NestedScrollingParentHelper as a field and delegate any View or ViewGroup methods to the NestedScrollingParentHelper methods of the same signature.

Views invoking nested scrolling functionality should always do so from the relevant ViewCompat, ViewGroupCompat or ViewParentCompat compatibility shim static methods. This ensures interoperability with nested scrolling views on all versions of Android.

Summary

Public methods

abstract void onNestedPreScroll(View target, int dx, int dy, int[] consumed, int type)

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

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

React to a nested scroll in progress.

abstract void onNestedScrollAccepted(View child, View target, int axes, int type)

React to the successful claiming of a nested scroll operation.

abstract boolean onStartNestedScroll(View child, View target, int axes, int type)

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

abstract void onStopNestedScroll(View target, int type)

React to a nested scroll operation ending.

Inherited methods

From interface android.support.v4.view.NestedScrollingParent

Public methods

onNestedPreScroll

added in version 26.1.0
void onNestedPreScroll (View target, 
                int dx, 
                int dy, 
                int[] consumed, 
                int type)

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 opportunity to consume the scroll before the nested scrolling child does. An example of this is a drawer that contains a scrollable list. The user will want to be able to scroll the list fully into view before the list itself begins scrolling.

onNestedPreScroll is called when a nested scrolling child invokes dispatchNestedPreScroll(int, int, int[], int[]). The implementation should report how any pixels of the scroll reported by dx, dy were consumed in the consumed 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: View that initiated the nested scroll

dx int: Horizontal scroll distance in pixels

dy int: Vertical scroll distance in pixels

consumed int: Output. The horizontal and vertical scroll distance consumed by this parent

type int: the type of input which cause this scroll event

onNestedScroll

added in version 26.1.0
void onNestedScroll (View target, 
                int dxConsumed, 
                int dyConsumed, 
                int dxUnconsumed, 
                int dyUnconsumed, 
                int type)

React to a nested scroll in progress.

This method will be called when the ViewParent's current nested scrolling child view dispatches a nested scroll event. To receive calls to this method the ViewParent must have previously returned true for a call to onStartNestedScroll(View, View, int, int).

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

Parameters
target View: The descendent view controlling the nested scroll

dxConsumed int: Horizontal scroll distance in pixels already consumed by target

dyConsumed int: Vertical scroll distance in pixels already consumed by target

dxUnconsumed int: Horizontal scroll distance in pixels not consumed by target

dyUnconsumed int: Vertical scroll distance in pixels not consumed by target

type int: the type of input which cause this scroll event

onNestedScrollAccepted

added in version 26.1.0
void onNestedScrollAccepted (View child, 
                View target, 
                int axes, 
                int type)

React to the successful claiming of a nested scroll operation.

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

Parameters
child View: Direct child of this ViewParent containing target

target View: View that initiated the nested scroll

axes int: Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

type int: the type of input which cause this scroll event

onStartNestedScroll

added in version 26.1.0
boolean onStartNestedScroll (View child, 
                View target, 
                int axes, 
                int type)

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

This method will be called in response to a descendant view invoking startNestedScroll(View, int). Each parent up the view hierarchy will be given an opportunity to respond and claim the nested scrolling operation by returning true.

This method may be overridden by ViewParent implementations to indicate when the view is willing to support a nested scrolling operation that is about to begin. If it returns true, this ViewParent will become the target view's nested scrolling parent for the duration of the scroll operation in progress. When the nested scroll is finished this ViewParent will receive a call to onStopNestedScroll(View, int).

Parameters
child View: Direct child of this ViewParent containing target

target View: View that initiated the nested scroll

axes int: Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

type int: the type of input which cause this scroll event

Returns
boolean true if this ViewParent accepts the nested scroll operation

onStopNestedScroll

added in version 26.1.0
void onStopNestedScroll (View target, 
                int type)

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 touch scroll ends with a ACTION_UP or ACTION_CANCEL event. Implementations of this method should always call their superclass's implementation of this method if one is present.

Parameters
target View: View that initiated the nested scroll

type int: the type of input which cause this scroll event