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

NestedScrollingChild2

public interface NestedScrollingChild2
implements NestedScrollingChild

android.support.v4.view.NestedScrollingChild2
Known Indirect Subclasses


This interface should be implemented by View subclasses that wish to support dispatching nested scrolling operations to a cooperating parent ViewGroup.

Classes implementing this interface should create a final instance of a NestedScrollingChildHelper as a field and delegate any View methods to the NestedScrollingChildHelper 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 boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow, int type)

Dispatch one step of a nested scroll in progress before this view consumes any portion of it.

abstract boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow, int type)

Dispatch one step of a nested scroll in progress.

abstract boolean hasNestedScrollingParent(int type)

Returns true if this view has a nested scrolling parent for the given input type.

abstract boolean startNestedScroll(int axes, int type)

Begin a nestable scroll operation along the given axes, for the given input type.

abstract void stopNestedScroll(int type)

Stop a nested scroll in progress for the given input type.

Inherited methods

From interface android.support.v4.view.NestedScrollingChild

Public methods

dispatchNestedPreScroll

added in version 26.1.0
boolean dispatchNestedPreScroll (int dx, 
                int dy, 
                int[] consumed, 
                int[] offsetInWindow, 
                int type)

Dispatch one step of a nested scroll in progress before this view consumes any portion of it.

Nested pre-scroll events are to nested scroll events what touch intercept is to touch. dispatchNestedPreScroll offers an opportunity for the parent view in a nested scrolling operation to consume some or all of the scroll operation before the child view consumes it.

Parameters
dx int: Horizontal scroll distance in pixels

dy int: Vertical scroll distance in pixels

consumed int: Output. If not null, consumed[0] will contain the consumed component of dx and consumed[1] the consumed dy.

offsetInWindow int: Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking.

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

Returns
boolean true if the parent consumed some or all of the scroll delta

dispatchNestedScroll

added in version 26.1.0
boolean dispatchNestedScroll (int dxConsumed, 
                int dyConsumed, 
                int dxUnconsumed, 
                int dyUnconsumed, 
                int[] offsetInWindow, 
                int type)

Dispatch one step of a nested scroll in progress.

Implementations of views that support nested scrolling should call this to report info about a scroll in progress to the current nested scrolling parent. If a nested scroll is not currently in progress or nested scrolling is not enabled for this view this method does nothing.

Compatible View implementations should also call dispatchNestedPreScroll before consuming a component of the scroll event themselves.

Parameters
dxConsumed int: Horizontal distance in pixels consumed by this view during this scroll step

dyConsumed int: Vertical distance in pixels consumed by this view during this scroll step

dxUnconsumed int: Horizontal scroll distance in pixels not consumed by this view

dyUnconsumed int: Horizontal scroll distance in pixels not consumed by this view

offsetInWindow int: Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking.

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

Returns
boolean true if the event was dispatched, false if it could not be dispatched.

hasNestedScrollingParent

added in version 26.1.0
boolean hasNestedScrollingParent (int type)

Returns true if this view has a nested scrolling parent for the given input type.

The presence of a nested scrolling parent indicates that this view has initiated a nested scroll and it was accepted by an ancestor view further up the view hierarchy.

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

Returns
boolean whether this view has a nested scrolling parent

startNestedScroll

added in version 26.1.0
boolean startNestedScroll (int axes, 
                int type)

Begin a nestable scroll operation along the given axes, for the given input type.

A view starting a nested scroll promises to abide by the following contract:

The view will call startNestedScroll upon initiating a scroll operation. In the case of a touch scroll type this corresponds to the initial ACTION_DOWN. In the case of touch scrolling the nested scroll will be terminated automatically in the same manner as requestDisallowInterceptTouchEvent(boolean). In the event of programmatic scrolling the caller must explicitly call stopNestedScroll(int) to indicate the end of the nested scroll.

If startNestedScroll returns true, a cooperative parent was found. If it returns false the caller may ignore the rest of this contract until the next scroll. Calling startNestedScroll while a nested scroll is already in progress will return true.

At each incremental step of the scroll the caller should invoke dispatchNestedPreScroll once it has calculated the requested scrolling delta. If it returns true the nested scrolling parent at least partially consumed the scroll and the caller should adjust the amount it scrolls by.

After applying the remainder of the scroll delta the caller should invoke dispatchNestedScroll, passing both the delta consumed and the delta unconsumed. A nested scrolling parent may treat these values differently. See onNestedScroll(View, int, int, int, int, int).

Parameters
axes int: Flags consisting of a combination of SCROLL_AXIS_HORIZONTAL and/or SCROLL_AXIS_VERTICAL.

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

Returns
boolean true if a cooperative parent was found and nested scrolling has been enabled for the current gesture.

stopNestedScroll

added in version 26.1.0
void stopNestedScroll (int type)

Stop a nested scroll in progress for the given input type.

Calling this method when a nested scroll is not currently in progress is harmless.

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