android.view.ViewParent |
Known Indirect Subclasses |
Defines the responsibilities for a class that will be a parent of a View. This is the API that a view sees when it wants to interact with its parent.
Public Methods | |||||||||||
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Change the z order of the child so it's on top of all other children.
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Tells if this view parent can resolve the layout direction.
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Tells if this view parent can resolve the text alignment.
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Tells if this view parent can resolve the text direction.
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This method is called on the parent when a child's drawable state
has changed.
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Called when a child view now has or no longer is tracking transient state.
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Called when a child of this parent is giving up focus
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Have the parent populate the specified context menu if it has anything to
add (and then recurse on its parent).
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Find the nearest view in the specified direction that wants to take focus
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Tells the parent that a new focusable view has become available.
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Compute the visible part of a rectangular region defined in terms of a child view's
coordinates.
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Return this view parent layout direction.
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Returns the parent if it exists, or null.
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Gets the parent of a given View for accessibility.
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Return this view parent text alignment.
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Return this view parent text direction.
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All or part of a child is dirty and needs to be redrawn.
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All or part of a child is dirty and needs to be redrawn.
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Tells if this view parent layout direction is resolved.
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Indicates whether layout was requested on this view parent.
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Tells if this view parent text alignment is resolved.
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Tells if this view parent text direction is resolved.
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Notifies a view parent that the accessibility state of one of its
descendants has changed and that the structure of the subtree is
different.
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Request a fling from a nested scroll.
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React to a nested scroll in progress before the target view consumes a portion of the scroll.
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React to a nested scroll in progress.
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React to the successful claiming of a nested scroll operation.
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React to a descendant view initiating a nestable scroll operation, claiming the
nested scroll operation if appropriate.
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React to a nested scroll operation ending.
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Tell view hierarchy that the global view attributes need to be
re-evaluated.
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Called when a child of this parent wants focus
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Called when a child of this group wants a particular rectangle to be
positioned onto the screen.
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Called when a child does not want this parent and its ancestors to
intercept touch events with
onInterceptTouchEvent(MotionEvent) . | |||||||||||
Ask that a new dispatch of
View.fitSystemWindows(Rect) be performed. | |||||||||||
Called when something has changed which has invalidated the layout of a
child of this view parent.
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Called by a child to request from its parent to send an
AccessibilityEvent . | |||||||||||
Called when a child wants the view hierarchy to gather and report
transparent regions to the window compositor.
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Bring up a context menu for the specified view or its ancestors.
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Start an action mode for the specified view.
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Change the z order of the child so it's on top of all other children.
This ordering change may affect layout, if this container
uses an order-dependent layout scheme (e.g., LinearLayout). Prior
to KITKAT
this
method should be followed by calls to requestLayout()
and
invalidate()
on this parent to force the parent to redraw
with the new child ordering.
child | The child to bring to the top of the z order |
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Tells if this view parent can resolve the layout direction.
See setLayoutDirection(int)
Tells if this view parent can resolve the text alignment.
See setTextAlignment(int)
Tells if this view parent can resolve the text direction.
See setTextDirection(int)
This method is called on the parent when a child's drawable state has changed.
child | The child whose drawable state has changed. |
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Called when a child view now has or no longer is tracking transient state.
"Transient state" is any state that a View might hold that is not expected to be reflected in the data model that the View currently presents. This state only affects the presentation to the user within the View itself, such as the current state of animations in progress or the state of a text selection operation.
Transient state is useful for hinting to other components of the View system
that a particular view is tracking something complex but encapsulated.
A ListView
for example may acknowledge that list item Views
with transient state should be preserved within their position or stable item ID
instead of treating that view as trivially replaceable by the backing adapter.
This allows adapter implementations to be simpler instead of needing to track
the state of item view animations in progress such that they could be restored
in the event of an unexpected recycling and rebinding of attached item views.
This method is called on a parent view when a child view or a view within its subtree begins or ends tracking of internal transient state.
child | Child view whose state has changed |
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hasTransientState | true if this child has transient state |
Called when a child of this parent is giving up focus
child | The view that is giving up focus |
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Have the parent populate the specified context menu if it has anything to add (and then recurse on its parent).
menu | The menu to populate |
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Find the nearest view in the specified direction that wants to take focus
v | The view that currently has focus |
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direction | One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT |
Tells the parent that a new focusable view has become available. This is to handle transitions from the case where there are no focusable views to the case where the first focusable view appears.
v | The view that has become newly focusable |
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Compute the visible part of a rectangular region defined in terms of a child view's coordinates.
Returns the clipped visible part of the rectangle r
, defined in the
child
's local coordinate system. r
is modified by this method to
contain the result, expressed in the global (root) coordinate system.
The resulting rectangle is always axis aligned. If a rotation is applied to a node in the View hierarchy, the result is the axis-aligned bounding box of the visible rectangle.
child | A child View, whose rectangular visible region we want to compute |
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r | The input rectangle, defined in the child coordinate system. Will be overwritten to contain the resulting visible rectangle, expressed in global (root) coordinates |
offset | The input coordinates of a point, defined in the child coordinate system.
As with the r parameter, this will be overwritten to contain the global (root)
coordinates of that point.
A null value is valid (in case you are not interested in this result) |
Return this view parent layout direction. See getLayoutDirection()
LAYOUT_DIRECTION_RTL
if the layout direction is RTL or returns
LAYOUT_DIRECTION_LTR
if the layout direction is not RTL.
Returns the parent if it exists, or null.
Gets the parent of a given View for accessibility. Since some Views are not exposed to the accessibility layer the parent for accessibility is not necessarily the direct parent of the View, rather it is a predecessor.
null
if no such is found.
Return this view parent text alignment. See getTextAlignment()
TEXT_ALIGNMENT_GRAVITY
,
TEXT_ALIGNMENT_CENTER
,
TEXT_ALIGNMENT_TEXT_START
,
TEXT_ALIGNMENT_TEXT_END
,
TEXT_ALIGNMENT_VIEW_START
,
TEXT_ALIGNMENT_VIEW_END
Return this view parent text direction. See getTextDirection()
TEXT_DIRECTION_FIRST_STRONG
TEXT_DIRECTION_ANY_RTL
,
TEXT_DIRECTION_LTR
,
TEXT_DIRECTION_RTL
,
TEXT_DIRECTION_LOCALE
All or part of a child is dirty and needs to be redrawn.
child | The child which is dirty |
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r | The area within the child that is invalid |
All or part of a child is dirty and needs to be redrawn.
The location array is an array of two int values which respectively define the left and the top position of the dirty child.
This method must return the parent of this ViewParent if the specified rectangle must be invalidated in the parent. If the specified rectangle does not require invalidation in the parent or if the parent does not exist, this method must return null.
When this method returns a non-null value, the location array must have been updated with the left and top coordinates of this ViewParent.
location | An array of 2 ints containing the left and top coordinates of the child to invalidate |
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r | The area within the child that is invalid |
Tells if this view parent layout direction is resolved.
See setLayoutDirection(int)
Indicates whether layout was requested on this view parent.
Tells if this view parent text alignment is resolved.
See setTextAlignment(int)
Tells if this view parent text direction is resolved.
See setTextDirection(int)
Notifies a view parent that the accessibility state of one of its descendants has changed and that the structure of the subtree is different.
child | The direct child whose subtree has changed. |
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source | The descendant view that changed. |
changeType | A bit mask of the types of changes that occurred. One or more of: |
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.
target | View that initiated the nested scroll |
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velocityX | Horizontal velocity in pixels per second. |
velocityY | Vertical velocity in pixels per second |
consumed | true if the child consumed the fling, false otherwise |
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(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 scroll |
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dx | Horizontal scroll distance in pixels |
dy | Vertical scroll distance in pixels |
consumed | Output. The horizontal and vertical scroll distance consumed by this parent |
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(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 scroll |
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dxConsumed | Horizontal scroll distance in pixels already consumed by target |
dyConsumed | Vertical scroll distance in pixels already consumed by target |
dxUnconsumed | Horizontal scroll distance in pixels not consumed by target |
dyUnconsumed | Vertical scroll distance in pixels not consumed by target |
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.
child | Direct child of this ViewParent containing target |
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target | View that initiated the nested scroll |
nestedScrollAxes | Flags consisting of SCROLL_AXIS_HORIZONTAL ,
SCROLL_AXIS_VERTICAL or both |
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(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(View)
.
child | Direct child of this ViewParent containing target |
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target | View that initiated the nested scroll |
nestedScrollAxes | Flags consisting of SCROLL_AXIS_HORIZONTAL ,
SCROLL_AXIS_VERTICAL or both |
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.
target | View that initiated the nested scroll |
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Tell view hierarchy that the global view attributes need to be re-evaluated.
child | View whose attributes have changed. |
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Called when a child of this parent wants focus
child | The child of this ViewParent that wants focus. This view will contain the focused view. It is not necessarily the view that actually has focus. |
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focused | The view that is a descendant of child that actually has focus |
Called when a child of this group wants a particular rectangle to be
positioned onto the screen. ViewGroup
s overriding this can trust
that:
ViewGroup
s overriding this should uphold the contract:
child | The direct child making the request. |
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rectangle | The rectangle in the child's coordinates the child wishes to be on the screen. |
immediate | True to forbid animated or delayed scrolling, false otherwise |
Called when a child does not want this parent and its ancestors to
intercept touch events with
onInterceptTouchEvent(MotionEvent)
.
This parent should pass this call onto its parents. This parent must obey this request for the duration of the touch (that is, only clear the flag after this parent has received an up or a cancel.
disallowIntercept | True if the child does not want the parent to intercept touch events. |
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Ask that a new dispatch of View.fitSystemWindows(Rect)
be performed.
Called when something has changed which has invalidated the layout of a child of this view parent. This will schedule a layout pass of the view tree.
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.
child | The child which requests sending the event. |
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event | The event to be sent. |
Called when a child wants the view hierarchy to gather and report transparent regions to the window compositor. Views that "punch" holes in the view hierarchy, such as SurfaceView can use this API to improve performance of the system. When no such a view is present in the hierarchy, this optimization in unnecessary and might slightly reduce the view hierarchy performance.
child | the view requesting the transparent region computation |
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Bring up a context menu for the specified view or its ancestors.
In most cases, a subclass does not need to override this. However, if
the subclass is added directly to the window manager (for example,
addView(View, android.view.ViewGroup.LayoutParams)
)
then it should override this and show the context menu.
originalView | The source view where the context menu was first invoked |
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Start an action mode for the specified view.
In most cases, a subclass does not need to override this. However, if the
subclass is added directly to the window manager (for example,
addView(View, android.view.ViewGroup.LayoutParams)
)
then it should override this and start the action mode.
originalView | The source view where the action mode was first invoked |
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callback | The callback that will handle lifecycle events for the action mode |