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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.view;
import android.annotation.NonNull;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.accessibility.AccessibilityEvent;
/**
* 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 interface ViewParent {
/**
* 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.
*/
public void requestLayout();
/**
* Indicates whether layout was requested on this view parent.
*
* @return true if layout was requested, false otherwise
*/
public boolean isLayoutRequested();
/**
* 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.
*
* @param child the view requesting the transparent region computation
*
*/
public void requestTransparentRegion(View child);
/**
* The target View has been invalidated, or has had a drawing property changed that
* requires the hierarchy to re-render.
*
* This method is called by the View hierarchy to signal ancestors that a View either needs to
* re-record its drawing commands, or drawing properties have changed. This is how Views
* schedule a drawing traversal.
*
* This signal is generally only dispatched for attached Views, since only they need to draw.
*
* @param child Direct child of this ViewParent containing target
* @param target The view that needs to redraw
*/
default void onDescendantInvalidated(@NonNull View child, @NonNull View target) {
if (getParent() != null) {
// Note: should pass 'this' as default, but can't since we may not be a View
getParent().onDescendantInvalidated(child, target);
}
}
/**
* All or part of a child is dirty and needs to be redrawn.
*
* @param child The child which is dirty
* @param r The area within the child that is invalid
*
* @deprecated Use {@link #onDescendantInvalidated(View, View)} instead.
*/
@Deprecated
public void invalidateChild(View child, Rect r);
/**
* 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.
*
* @param location An array of 2 ints containing the left and top
* coordinates of the child to invalidate
* @param r The area within the child that is invalid
*
* @return the parent of this ViewParent or null
*
* @deprecated Use {@link #onDescendantInvalidated(View, View)} instead.
*/
@Deprecated
public ViewParent invalidateChildInParent(int[] location, Rect r);
/**
* Returns the parent if it exists, or null.
*
* @return a ViewParent or null if this ViewParent does not have a parent
*/
public ViewParent getParent();
/**
* Called when a child of this parent wants focus
*
* @param 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.
* @param focused The view that is a descendant of child that actually has
* focus
*/
public void requestChildFocus(View child, View focused);
/**
* Tell view hierarchy that the global view attributes need to be
* re-evaluated.
*
* @param child View whose attributes have changed.
*/
public void recomputeViewAttributes(View child);
/**
* Called when a child of this parent is giving up focus
*
* @param child The view that is giving up focus
*/
public void clearChildFocus(View child);
/**
* 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.
*
* @param child A child View, whose rectangular visible region we want to compute
* @param r The input rectangle, defined in the child coordinate system. Will be overwritten to
* contain the resulting visible rectangle, expressed in global (root) coordinates
* @param 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 true if the resulting rectangle is not empty, false otherwise
*/
public boolean getChildVisibleRect(View child, Rect r, android.graphics.Point offset);
/**
* Find the nearest view in the specified direction that wants to take focus
*
* @param v The view that currently has focus
* @param direction One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT
*/
public View focusSearch(View v, int direction);
/**
* Find the nearest keyboard navigation cluster in the specified direction.
* This does not actually give focus to that cluster.
*
* @param currentCluster The starting point of the search. Null means the current cluster is not
* found yet
* @param direction Direction to look
*
* @return The nearest keyboard navigation cluster in the specified direction, or null if none
* can be found
*/
View keyboardNavigationClusterSearch(View currentCluster, int direction);
/**
* 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 {@link android.os.Build.VERSION_CODES#KITKAT} this
* method should be followed by calls to {@link #requestLayout()} and
* {@link View#invalidate()} on this parent to force the parent to redraw
* with the new child ordering.
*
* @param child The child to bring to the top of the z order
*/
public void bringChildToFront(View child);
/**
* 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.
*
* @param v The view that has become newly focusable
*/
public void focusableViewAvailable(View v);
/**
* Shows the 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,
* {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)})
* then it should override this and show the context menu.
*
* @param originalView the source view where the context menu was first
* invoked
* @return {@code true} if the context menu was shown, {@code false}
* otherwise
* @see #showContextMenuForChild(View, float, float)
*/
public boolean showContextMenuForChild(View originalView);
/**
* Shows the context menu for the specified view or its ancestors anchored
* to the specified view-relative coordinate.
*
* In most cases, a subclass does not need to override this. However, if
* the subclass is added directly to the window manager (for example,
* {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)})
* then it should override this and show the context menu.
*
* If a subclass overrides this method it should also override
* {@link #showContextMenuForChild(View)}.
*
* @param originalView the source view where the context menu was first
* invoked
* @param x the X coordinate in pixels relative to the original view to
* which the menu should be anchored, or {@link Float#NaN} to
* disable anchoring
* @param y the Y coordinate in pixels relative to the original view to
* which the menu should be anchored, or {@link Float#NaN} to
* disable anchoring
* @return {@code true} if the context menu was shown, {@code false}
* otherwise
*/
boolean showContextMenuForChild(View originalView, float x, float y);
/**
* Have the parent populate the specified context menu if it has anything to
* add (and then recurse on its parent).
*
* @param menu The menu to populate
*/
public void createContextMenu(ContextMenu menu);
/**
* Start an action mode for the specified view with the default type
* {@link ActionMode#TYPE_PRIMARY}.
*
*
In most cases, a subclass does not need to override this. However, if the
* subclass is added directly to the window manager (for example,
* {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)})
* then it should override this and start the action mode.
*
* @param originalView The source view where the action mode was first invoked
* @param callback The callback that will handle lifecycle events for the action mode
* @return The new action mode if it was started, null otherwise
*
* @see #startActionModeForChild(View, android.view.ActionMode.Callback, int)
*/
public ActionMode startActionModeForChild(View originalView, ActionMode.Callback callback);
/**
* Start an action mode of a specific type 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,
* {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)})
* then it should override this and start the action mode.
*
* @param originalView The source view where the action mode was first invoked
* @param callback The callback that will handle lifecycle events for the action mode
* @param type One of {@link ActionMode#TYPE_PRIMARY} or {@link ActionMode#TYPE_FLOATING}.
* @return The new action mode if it was started, null otherwise
*/
public ActionMode startActionModeForChild(
View originalView, ActionMode.Callback callback, int type);
/**
* This method is called on the parent when a child's drawable state
* has changed.
*
* @param child The child whose drawable state has changed.
*/
public void childDrawableStateChanged(View child);
/**
* Called when a child does not want this parent and its ancestors to
* intercept touch events with
* {@link ViewGroup#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.
*
* @param disallowIntercept True if the child does not want the parent to
* intercept touch events.
*/
public void requestDisallowInterceptTouchEvent(boolean disallowIntercept);
/**
* Called when a child of this group wants a particular rectangle to be
* positioned onto the screen. {@link ViewGroup}s overriding this can trust
* that:
*
* - child will be a direct child of this group
* - rectangle will be in the child's content coordinates
*
*
* {@link ViewGroup}s overriding this should uphold the contract:
*
* - nothing will change if the rectangle is already visible
* - the view port will be scrolled only just enough to make the
* rectangle visible
*
*
* @param child The direct child making the request.
* @param rectangle The rectangle in the child's coordinates the child
* wishes to be on the screen.
* @param immediate True to forbid animated or delayed scrolling,
* false otherwise
* @return Whether the group scrolled to handle the operation
*/
public boolean requestChildRectangleOnScreen(View child, Rect rectangle,
boolean immediate);
/**
* Called by a child to request from its parent to send an {@link 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.
*
* @param child The child which requests sending the event.
* @param event The event to be sent.
* @return True if the event was sent.
*/
public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event);
/**
* 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.
*
* @param child Child view whose state has changed
* @param hasTransientState true if this child has transient state
*/
public void childHasTransientStateChanged(View child, boolean hasTransientState);
/**
* Ask that a new dispatch of {@link View#fitSystemWindows(Rect)
* View.fitSystemWindows(Rect)} be performed.
*/
public void requestFitSystemWindows();
/**
* 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.
*
* @return The parent or null if no such is found.
*/
public ViewParent getParentForAccessibility();
/**
* Notifies a view parent that the accessibility state of one of its
* descendants has changed and that the structure of the subtree is
* different.
* @param child The direct child whose subtree has changed.
* @param source The descendant view that changed. May not be {@code null}.
* @param changeType A bit mask of the types of changes that occurred. One
* or more of:
*
* - {@link AccessibilityEvent#CONTENT_CHANGE_TYPE_CONTENT_DESCRIPTION}
*
- {@link AccessibilityEvent#CONTENT_CHANGE_TYPE_SUBTREE}
*
- {@link AccessibilityEvent#CONTENT_CHANGE_TYPE_TEXT}
*
- {@link AccessibilityEvent#CONTENT_CHANGE_TYPE_UNDEFINED}
*
*/
public void notifySubtreeAccessibilityStateChanged(
View child, @NonNull View source, int changeType);
/**
* Tells if this view parent can resolve the layout direction.
* See {@link View#setLayoutDirection(int)}
*
* @return True if this view parent can resolve the layout direction.
*/
public boolean canResolveLayoutDirection();
/**
* Tells if this view parent layout direction is resolved.
* See {@link View#setLayoutDirection(int)}
*
* @return True if this view parent layout direction is resolved.
*/
public boolean isLayoutDirectionResolved();
/**
* Return this view parent layout direction. See {@link View#getLayoutDirection()}
*
* @return {@link View#LAYOUT_DIRECTION_RTL} if the layout direction is RTL or returns
* {@link View#LAYOUT_DIRECTION_LTR} if the layout direction is not RTL.
*/
public int getLayoutDirection();
/**
* Tells if this view parent can resolve the text direction.
* See {@link View#setTextDirection(int)}
*
* @return True if this view parent can resolve the text direction.
*/
public boolean canResolveTextDirection();
/**
* Tells if this view parent text direction is resolved.
* See {@link View#setTextDirection(int)}
*
* @return True if this view parent text direction is resolved.
*/
public boolean isTextDirectionResolved();
/**
* Return this view parent text direction. See {@link View#getTextDirection()}
*
* @return the resolved text direction. Returns one of:
*
* {@link View#TEXT_DIRECTION_FIRST_STRONG}
* {@link View#TEXT_DIRECTION_ANY_RTL},
* {@link View#TEXT_DIRECTION_LTR},
* {@link View#TEXT_DIRECTION_RTL},
* {@link View#TEXT_DIRECTION_LOCALE}
*/
public int getTextDirection();
/**
* Tells if this view parent can resolve the text alignment.
* See {@link View#setTextAlignment(int)}
*
* @return True if this view parent can resolve the text alignment.
*/
public boolean canResolveTextAlignment();
/**
* Tells if this view parent text alignment is resolved.
* See {@link View#setTextAlignment(int)}
*
* @return True if this view parent text alignment is resolved.
*/
public boolean isTextAlignmentResolved();
/**
* Return this view parent text alignment. See {@link android.view.View#getTextAlignment()}
*
* @return the resolved text alignment. Returns one of:
*
* {@link View#TEXT_ALIGNMENT_GRAVITY},
* {@link View#TEXT_ALIGNMENT_CENTER},
* {@link View#TEXT_ALIGNMENT_TEXT_START},
* {@link View#TEXT_ALIGNMENT_TEXT_END},
* {@link View#TEXT_ALIGNMENT_VIEW_START},
* {@link View#TEXT_ALIGNMENT_VIEW_END}
*/
public int getTextAlignment();
/**
* 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
* {@link View#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 {@link #onStopNestedScroll(View)}.
*
*
* @param child Direct child of this ViewParent containing target
* @param target View that initiated the nested scroll
* @param nestedScrollAxes Flags consisting of {@link View#SCROLL_AXIS_HORIZONTAL},
* {@link View#SCROLL_AXIS_VERTICAL} or both
* @return true if this ViewParent accepts the nested scroll operation
*/
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes);
/**
* React to the successful claiming of a nested scroll operation.
*
* This method will be called after
* {@link #onStartNestedScroll(View, View, int) 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.
*
* @param child Direct child of this ViewParent containing target
* @param target View that initiated the nested scroll
* @param nestedScrollAxes Flags consisting of {@link View#SCROLL_AXIS_HORIZONTAL},
* {@link View#SCROLL_AXIS_VERTICAL} or both
* @see #onStartNestedScroll(View, View, int)
* @see #onStopNestedScroll(View)
*/
public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes);
/**
* 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 {@link MotionEvent#ACTION_UP} or {@link MotionEvent#ACTION_CANCEL} event.
* Implementations of this method should always call their superclass's implementation of this
* method if one is present.
*
* @param target View that initiated the nested scroll
*/
public void onStopNestedScroll(View target);
/**
* 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
* {@link #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.
*
* @param target The descendent view controlling the nested scroll
* @param dxConsumed Horizontal scroll distance in pixels already consumed by target
* @param dyConsumed Vertical scroll distance in pixels already consumed by target
* @param dxUnconsumed Horizontal scroll distance in pixels not consumed by target
* @param dyUnconsumed Vertical scroll distance in pixels not consumed by target
*/
public void onNestedScroll(View target, int dxConsumed, int dyConsumed,
int dxUnconsumed, int dyUnconsumed);
/**
* 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
* {@link View#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.
*
* @param target View that initiated the nested scroll
* @param dx Horizontal scroll distance in pixels
* @param dy Vertical scroll distance in pixels
* @param consumed Output. The horizontal and vertical scroll distance consumed by this parent
*/
public void onNestedPreScroll(View target, int dx, int dy, int[] 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
* {@link VelocityTracker velocity} in the direction of scrolling that meets or exceeds
* the {@link ViewConfiguration#getScaledMinimumFlingVelocity() 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.
*
* @param target View that initiated the nested scroll
* @param velocityX Horizontal velocity in pixels per second
* @param velocityY Vertical velocity in pixels per second
* @param consumed true if the child consumed the fling, false otherwise
* @return true if this parent consumed or otherwise reacted to the fling
*/
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed);
/**
* 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
* {@link VelocityTracker velocity} in the direction of scrolling that meets or exceeds
* the {@link ViewConfiguration#getScaledMinimumFlingVelocity() minimum fling velocity}
* along a scrollable axis.
*
* If a nested scrolling parent is consuming motion as part of a
* {@link #onNestedPreScroll(View, int, int, int[]) 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.
*
* @param target View that initiated the nested scroll
* @param velocityX Horizontal velocity in pixels per second
* @param velocityY Vertical velocity in pixels per second
* @return true if this parent consumed the fling ahead of the target view
*/
public boolean onNestedPreFling(View target, float velocityX, float velocityY);
/**
* React to an accessibility action delegated by a target descendant view before the target
* processes it.
*
* This method may be called by a target descendant view if the target wishes to give
* a view in its parent chain a chance to react to the event before normal processing occurs.
* Most commonly this will be a scroll event such as
* {@link android.view.accessibility.AccessibilityNodeInfo#ACTION_SCROLL_FORWARD}.
* A ViewParent that supports acting as a nested scrolling parent should override this
* method and act accordingly to implement scrolling via accesibility systems.
*
* @param target The target view dispatching this action
* @param action Action being performed; see
* {@link android.view.accessibility.AccessibilityNodeInfo}
* @param arguments Optional action arguments
* @return true if the action was consumed by this ViewParent
*/
public boolean onNestedPrePerformAccessibilityAction(View target, int action, Bundle arguments);
}