core/java/android/view/ViewParent.java

/*
 * 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.graphics.Rect;
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);

    /**
     * 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
     */
    public void invalidateChild(View child, Rect r);

    /**
     * All or part of a child is dirty and needs to be redrawn.
     *
     * <p>The location array is an array of two int values which respectively
     * define the left and the top position of the dirty child.</p>
     *
     * <p>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.</p>
     *
     * <p>When this method returns a non-null value, the location array must
     * have been updated with the left and top coordinates of this ViewParent.</p>
     *
     * @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
     */
    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.
     *
     * <p>Returns the clipped visible part of the rectangle <code>r</code>, defined in the
     * <code>child</code>'s local coordinate system. <code>r</code> is modified by this method to
     * contain the result, expressed in the global (root) coordinate system.</p>
     *
     * <p>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.</p>
     *
     * @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 <code>r</code> parameter, this will be overwritten to contain the global (root)
     * coordinates of that point.
     * A <code>null</code> 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);

    /**
     * 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#KEY_LIME_PIE} 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);

    /**
     * Bring up a context menu for the specified view or its ancestors.
     *
     * <p>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.</p>
     * 
     * @param originalView The source view where the context menu was first invoked
     * @return true if a context menu was displayed
     */
    public boolean showContextMenuForChild(View originalView);

    /**
     * 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.
     *
     * <p>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.</p>
     *
     * @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
     */
    public ActionMode startActionModeForChild(View originalView, ActionMode.Callback callback);

    /**
     * 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)}.
     *
     * <p>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.</p>
     * 
     * @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:
     * <ul>
     *   <li>child will be a direct child of this group</li>
     *   <li>rectangle will be in the child's coordinates</li>
     * </ul>
     *
     * <p>{@link ViewGroup}s overriding this should uphold the contract:</p>
     * <ul>
     *   <li>nothing will change if the rectangle is already visible</li>
     *   <li>the view port will be scrolled only just enough to make the
     *       rectangle visible</li>
     * <ul>
     *
     * @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.
     * <p>
     * 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.</p>
     *
     * @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.
     *
     * <p>"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.</p>
     *
     * <p>Transient state is useful for hinting to other components of the View system
     * that a particular view is tracking something complex but encapsulated.
     * A <code>ListView</code> 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.</p>
     *
     * <p>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.</p>
     *
     * @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 <code>null</code> if no such is found.
     */
    public ViewParent getParentForAccessibility();

    /**
     * A child notifies its parent that the accessibility state of a subtree rooted
     * at a given node changed. That is the structure of the subtree is different.
     *
     * @param root The root of the changed subtree.
     */
    public void childAccessibilityStateChanged(View root);

    /**
     * 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();
}