Android APIs
public class

NestedScrollingChildHelper

extends Object
java.lang.Object
   ↳ android.support.v4.view.NestedScrollingChildHelper

Class Overview

Helper class for implementing nested scrolling child views compatible with Android platform versions earlier than Android 5.0 Lollipop (API 21).

View subclasses should instantiate a final instance of this class as a field at construction. For each View method that has a matching method signature in this class, delegate the operation to the helper instance in an overriden method implementation. This implements the standard framework policy for nested scrolling.

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 Android 5.0 Lollipop and newer.

Summary

Public Constructors
NestedScrollingChildHelper(View view)
Construct a new helper for a given view.
Public Methods
boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed)
Dispatch a nested fling operation to the current nested scrolling parent.
boolean dispatchNestedPreFling(float velocityX, float velocityY)
Dispatch a nested pre-fling operation to the current nested scrolling parent.
boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow)
Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.
boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow)
Dispatch one step of a nested scrolling operation to the current nested scrolling parent.
boolean hasNestedScrollingParent()
Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress.
boolean isNestedScrollingEnabled()
Check if nested scrolling is enabled for this view.
void onDetachedFromWindow()
View subclasses should always call this method on their NestedScrollingChildHelper when detached from a window.
void onStopNestedScroll(View child)
Called when a nested scrolling child stops its current nested scroll operation.
void setNestedScrollingEnabled(boolean enabled)
Enable nested scrolling.
boolean startNestedScroll(int axes)
Start a new nested scroll for this view.
void stopNestedScroll()
Stop a nested scroll in progress.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public NestedScrollingChildHelper (View view)

Construct a new helper for a given view.

Public Methods

public boolean dispatchNestedFling (float velocityX, float velocityY, boolean consumed)

Dispatch a nested fling operation to the current nested scrolling parent.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if the parent consumed the nested fling

public boolean dispatchNestedPreFling (float velocityX, float velocityY)

Dispatch a nested pre-fling operation to the current nested scrolling parent.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if the parent consumed the nested fling

public boolean dispatchNestedPreScroll (int dx, int dy, int[] consumed, int[] offsetInWindow)

Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if the parent consumed any of the nested scroll

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

Dispatch one step of a nested scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if the parent consumed any of the nested scroll

public boolean hasNestedScrollingParent ()

Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if this view has a nested scrolling parent, false otherwise

public boolean isNestedScrollingEnabled ()

Check if nested scrolling is enabled for this view.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Returns
  • true if nested scrolling is enabled for this view

public void onDetachedFromWindow ()

View subclasses should always call this method on their NestedScrollingChildHelper when detached from a window.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

public void onStopNestedScroll (View child)

Called when a nested scrolling child stops its current nested scroll operation.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Parameters
child Child view stopping its nested scroll. This may not be a direct child view.

public void setNestedScrollingEnabled (boolean enabled)

Enable nested scrolling.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Parameters
enabled true to enable nested scrolling dispatch from this view, false otherwise

public boolean startNestedScroll (int axes)

Start a new nested scroll for this view.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.

Parameters
axes Supported nested scroll axes. See startNestedScroll(int).
Returns
  • true if a cooperating parent view was found and nested scrolling started successfully

public void stopNestedScroll ()

Stop a nested scroll in progress.

This is a delegate method. Call it from your View subclass method/NestedScrollingChild interface method with the same signature to implement the standard policy.