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ViewParentCompat

public final class ViewParentCompat
extends Object

java.lang.Object
   ↳ android.support.v4.view.ViewParentCompat


Helper for accessing features in ViewParent introduced after API level 4 in a backwards compatible fashion.

Summary

Public methods

static void notifySubtreeAccessibilityStateChanged(ViewParent parent, View child, View source, int changeType)

Notifies a view parent that the accessibility state of one of its descendants has changed and that the structure of the subtree is different.

static boolean onNestedFling(ViewParent parent, View target, float velocityX, float velocityY, boolean consumed)

Request a fling from a nested scroll.

static boolean onNestedPreFling(ViewParent parent, View target, float velocityX, float velocityY)

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

static void onNestedPreScroll(ViewParent parent, View target, int dx, int dy, int[] consumed)

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

static void onNestedScroll(ViewParent parent, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed)

React to a nested scroll in progress.

static void onNestedScrollAccepted(ViewParent parent, View child, View target, int nestedScrollAxes)

React to the successful claiming of a nested scroll operation.

static boolean onStartNestedScroll(ViewParent parent, View child, View target, int nestedScrollAxes)

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

static void onStopNestedScroll(ViewParent parent, View target)

React to a nested scroll operation ending.

static boolean requestSendAccessibilityEvent(ViewParent parent, View child, AccessibilityEvent event)

Called by a child to request from its parent to send an AccessibilityEvent.

Inherited methods

From class java.lang.Object

Public methods

notifySubtreeAccessibilityStateChanged

void notifySubtreeAccessibilityStateChanged (ViewParent parent, 
                View child, 
                View source, 
                int changeType)

Notifies a view parent that the accessibility state of one of its descendants has changed and that the structure of the subtree is different.

Parameters
parent ViewParent
child View: The direct child whose subtree has changed.
source View: The descendant view that changed.
changeType int: A bit mask of the types of changes that occurred. One or more of:

onNestedFling

boolean onNestedFling (ViewParent parent, 
                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
parent ViewParent
target View: View that initiated the nested scroll
velocityX float: Horizontal velocity in pixels per second
velocityY float: Vertical velocity in pixels per second
consumed boolean: true if the child consumed the fling, false otherwise
Returns
boolean true if this parent consumed or otherwise reacted to the fling

onNestedPreFling

boolean onNestedPreFling (ViewParent parent, 
                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
parent ViewParent
target View: View that initiated the nested scroll
velocityX float: Horizontal velocity in pixels per second
velocityY float: Vertical velocity in pixels per second
Returns
boolean true if this parent consumed the fling ahead of the target view

onNestedPreScroll

void onNestedPreScroll (ViewParent parent, 
                View target, 
                int dx, 
                int dy, 
                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(View, 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
parent ViewParent
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

onNestedScroll

void onNestedScroll (ViewParent parent, 
                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(ViewParent, View, View, 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
parent ViewParent
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

onNestedScrollAccepted

void onNestedScrollAccepted (ViewParent parent, 
                View child, 
                View target, 
                int nestedScrollAxes)

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
parent ViewParent
child View: Direct child of this ViewParent containing target
target View: View that initiated the nested scroll
nestedScrollAxes int: Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

See also:

onStartNestedScroll

boolean onStartNestedScroll (ViewParent parent, 
                View child, 
                View target, 
                int nestedScrollAxes)

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(ViewParent, View).

Parameters
parent ViewParent
child View: Direct child of this ViewParent containing target
target View: View that initiated the nested scroll
nestedScrollAxes int: Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both
Returns
boolean true if this ViewParent accepts the nested scroll operation

onStopNestedScroll

void onStopNestedScroll (ViewParent parent, 
                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
parent ViewParent
target View: View that initiated the nested scroll

requestSendAccessibilityEvent

boolean requestSendAccessibilityEvent (ViewParent parent, 
                View child, 
                AccessibilityEvent event)

Called by a child to request from its parent to send an AccessibilityEvent. The child has already populated a record for itself in the event and is delegating to its parent to send the event. The parent can optionally add a record for itself.

Note: An accessibility event is fired by an individual view which populates the event with a record for its state and requests from its parent to perform the sending. The parent can optionally add a record for itself before dispatching the request to its parent. A parent can also choose not to respect the request for sending the event. The accessibility event is sent by the topmost view in the view tree.

Parameters
parent ViewParent: The parent whose method to invoke.
child View: The child which requests sending the event.
event AccessibilityEvent: The event to be sent.
Returns
boolean True if the event was sent.
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