NestedScrollingParent

Added in 1.1.0

public interface NestedScrollingParent

Known direct subclasses
NestedScrollingParent2

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

SwipeRefreshLayout

The SwipeRefreshLayout should be used whenever the user can refresh the contents of a view via a vertical swipe gesture.

WearableDrawerLayout

Top-level container that allows interactive drawers to be pulled from the top and bottom edge of the window.

Known indirect subclasses
CoordinatorLayout

CoordinatorLayout is a super-powered FrameLayout.

MotionLayout

A subclass of ConstraintLayout that supports animating between various states Added in 2.0

NestedScrollView

NestedScrollView is just like ScrollView, but it supports acting as both a nested scrolling parent and child on both new and old versions of Android.

NestedScrollingParent3

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

SwipeRefreshLayout

The SwipeRefreshLayout should be used whenever the user can refresh the contents of a view via a vertical swipe gesture.


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 Android 5.0 Lollipop and newer.

Summary

Public methods

abstract int

Return the current axes of nested scrolling for this NestedScrollingParent.

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

Request a fling from a nested scroll.

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

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

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

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

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

React to a nested scroll in progress.

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

React to the successful claiming of a nested scroll operation.

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

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

abstract void

React to a nested scroll operation ending.

Public methods

getNestedScrollAxes

Added in 1.1.0
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 in the hierarchy.

Returns
int

Flags indicating the current axes of nested scrolling

onNestedFling

Added in 1.1.0
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 conditions for a fling. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceeds the minimum fling velocity along a scrollable axis.

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

Parameters
@NonNull View target

View that initiated the nested scroll

float velocityX

Horizontal velocity in pixels per second

float velocityY

Vertical velocity in pixels per second

boolean consumed

true if the child consumed the fling, false otherwise

Returns
boolean

true if this parent consumed or otherwise reacted to the fling

onNestedPreFling

Added in 1.1.0
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 given velocity along each axis. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceeds the 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 for it to also consume the pre-fling to complete that same motion. By returning true from this method, the parent indicates that the child should not fling its own internal content as well.

Parameters
@NonNull View target

View that initiated the nested scroll

float velocityX

Horizontal velocity in pixels per second

float velocityY

Vertical velocity in pixels per second

Returns
boolean

true if this parent consumed the fling ahead of the target view

onNestedPreScroll

Added in 1.1.0
abstract void onNestedPreScroll(
    @NonNull View target,
    int dx,
    int dy,
    @NonNull 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 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. 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
@NonNull View target

View that initiated the nested scroll

int dx

Horizontal scroll distance in pixels

int dy

Vertical scroll distance in pixels

@NonNull int[] consumed

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

onNestedScroll

Added in 1.1.0
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 view dispatches a nested scroll event. To receive calls to this method the ViewParent must have previously returned true for a call to onStartNestedScroll.

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
@NonNull View target

The descendent view controlling the nested scroll

int dxConsumed

Horizontal scroll distance in pixels already consumed by target

int dyConsumed

Vertical scroll distance in pixels already consumed by target

int dxUnconsumed

Horizontal scroll distance in pixels not consumed by target

int dyUnconsumed

Vertical scroll distance in pixels not consumed by target

onNestedScrollAccepted

Added in 1.1.0
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 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
@NonNull View child

Direct child of this ViewParent containing target

@NonNull View target

View that initiated the nested scroll

int axes

Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

onStartNestedScroll

Added in 1.1.0
abstract boolean onStartNestedScroll(@NonNull View child, @NonNull View target, int axes)

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. 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.

Parameters
@NonNull View child

Direct child of this ViewParent containing target

@NonNull View target

View that initiated the nested scroll

int axes

Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

Returns
boolean

true if this ViewParent accepts the nested scroll operation

onStopNestedScroll

Added in 1.1.0
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 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
@NonNull View target

View that initiated the nested scroll