public final class ViewParentCompat extends Object
ViewParent
introduced after API level 4 in a backwards compatible fashion.Modifier and Type | Method and Description |
---|---|
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 . |
public static boolean requestSendAccessibilityEvent(ViewParent parent, View child, AccessibilityEvent event)
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.
parent
- The parent whose method to invoke.child
- The child which requests sending the event.event
- The event to be sent.public static boolean onStartNestedScroll(ViewParent parent, View child, View target, int nestedScrollAxes)
This method will be called in response to a descendant view invoking
ViewCompat.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)
.
child
- Direct child of this ViewParent containing targettarget
- View that initiated the nested scrollnestedScrollAxes
- Flags consisting of ViewCompat.SCROLL_AXIS_HORIZONTAL
,
ViewCompat.SCROLL_AXIS_VERTICAL
or bothpublic static void onNestedScrollAccepted(ViewParent parent, View child, View target, int nestedScrollAxes)
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.
child
- Direct child of this ViewParent containing targettarget
- View that initiated the nested scrollnestedScrollAxes
- Flags consisting of ViewCompat.SCROLL_AXIS_HORIZONTAL
,
ViewCompat.SCROLL_AXIS_VERTICAL
or bothonStartNestedScroll(ViewParent, View, View, int)
,
onStopNestedScroll(ViewParent, View)
public static void onStopNestedScroll(ViewParent parent, View target)
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 MotionEvent.ACTION_UP
or MotionEvent.ACTION_CANCEL
event.
Implementations of this method should always call their superclass's implementation of this
method if one is present.
target
- View that initiated the nested scrollpublic static void onNestedScroll(ViewParent parent, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed)
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.
target
- The descendent view controlling the nested scrolldxConsumed
- Horizontal scroll distance in pixels already consumed by targetdyConsumed
- Vertical scroll distance in pixels already consumed by targetdxUnconsumed
- Horizontal scroll distance in pixels not consumed by targetdyUnconsumed
- Vertical scroll distance in pixels not consumed by targetpublic static void onNestedPreScroll(ViewParent parent, View target, int dx, int dy, int[] consumed)
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
ViewCompat.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.
target
- View that initiated the nested scrolldx
- Horizontal scroll distance in pixelsdy
- Vertical scroll distance in pixelsconsumed
- Output. The horizontal and vertical scroll distance consumed by this parentpublic static boolean onNestedFling(ViewParent parent, View target, float velocityX, float velocityY, boolean consumed)
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.
target
- View that initiated the nested scrollvelocityX
- Horizontal velocity in pixels per secondvelocityY
- Vertical velocity in pixels per secondconsumed
- true if the child consumed the fling, false otherwisepublic static boolean onNestedPreFling(ViewParent parent, View target, float velocityX, float velocityY)
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.
target
- View that initiated the nested scrollvelocityX
- Horizontal velocity in pixels per secondvelocityY
- Vertical velocity in pixels per secondpublic static void notifySubtreeAccessibilityStateChanged(ViewParent parent, View child, View source, int changeType)
child
- The direct child whose subtree has changed.source
- The descendant view that changed.changeType
- A bit mask of the types of changes that occurred. One
or more of: