* This should be applied to the parent view using * {@link ViewCompat#setAccessibilityDelegate}: * *
* mAccessHelper = ExploreByTouchHelper.create(someView, mAccessHelperCallback); * ViewCompat.setAccessibilityDelegate(someView, mAccessHelper); **/ public abstract class ExploreByTouchHelper extends AccessibilityDelegateCompat { /** Virtual node identifier value for invalid nodes. */ public static final int INVALID_ID = Integer.MIN_VALUE; /** Default class name used for virtual views. */ private static final String DEFAULT_CLASS_NAME = View.class.getName(); // Temporary, reusable data structures. private final Rect mTempScreenRect = new Rect(); private final Rect mTempParentRect = new Rect(); private final Rect mTempVisibleRect = new Rect(); private final int[] mTempGlobalRect = new int[2]; /** System accessibility manager, used to check state and send events. */ private final AccessibilityManager mManager; /** View whose internal structure is exposed through this helper. */ private final View mView; /** Node provider that handles creating nodes and performing actions. */ private ExploreByTouchNodeProvider mNodeProvider; /** Virtual view id for the currently focused logical item. */ private int mFocusedVirtualViewId = INVALID_ID; /** Virtual view id for the currently hovered logical item. */ private int mHoveredVirtualViewId = INVALID_ID; /** * Factory method to create a new {@link ExploreByTouchHelper}. * * @param forView View whose logical children are exposed by this helper. */ public ExploreByTouchHelper(View forView) { if (forView == null) { throw new IllegalArgumentException("View may not be null"); } mView = forView; final Context context = forView.getContext(); mManager = (AccessibilityManager) context.getSystemService(Context.ACCESSIBILITY_SERVICE); } /** * Returns the {@link AccessibilityNodeProviderCompat} for this helper. * * @param host View whose logical children are exposed by this helper. * @return The accessibility node provider for this helper. */ @Override public AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View host) { if (mNodeProvider == null) { mNodeProvider = new ExploreByTouchNodeProvider(); } return mNodeProvider; } /** * Dispatches hover {@link MotionEvent}s to the virtual view hierarchy when * the Explore by Touch feature is enabled. *
* This method should be called by overriding * {@link View#dispatchHoverEvent}: * *
@Override
* public boolean dispatchHoverEvent(MotionEvent event) {
* if (mHelper.dispatchHoverEvent(this, event) {
* return true;
* }
* return super.dispatchHoverEvent(event);
* }
*
*
* @param event The hover event to dispatch to the virtual view hierarchy.
* @return Whether the hover event was handled.
*/
public boolean dispatchHoverEvent(MotionEvent event) {
if (!mManager.isEnabled()
|| !AccessibilityManagerCompat.isTouchExplorationEnabled(mManager)) {
return false;
}
switch (event.getAction()) {
case MotionEventCompat.ACTION_HOVER_MOVE:
case MotionEventCompat.ACTION_HOVER_ENTER:
final int virtualViewId = getVirtualViewAt(event.getX(), event.getY());
updateHoveredVirtualView(virtualViewId);
return (virtualViewId != INVALID_ID);
case MotionEventCompat.ACTION_HOVER_EXIT:
if (mFocusedVirtualViewId != INVALID_ID) {
updateHoveredVirtualView(INVALID_ID);
return true;
}
return false;
default:
return false;
}
}
/**
* Populates an event of the specified type with information about an item
* and attempts to send it up through the view hierarchy.
* * You should call this method after performing a user action that normally * fires an accessibility event, such as clicking on an item. * *
public void performItemClick(T item) {
* ...
* sendEventForVirtualViewId(item.id, AccessibilityEvent.TYPE_VIEW_CLICKED);
* }
*
*
* @param virtualViewId The virtual view id for which to send an event.
* @param eventType The type of event to send.
* @return true if the event was sent successfully.
*/
public boolean sendEventForVirtualView(int virtualViewId, int eventType) {
if ((virtualViewId == INVALID_ID) || !mManager.isEnabled()) {
return false;
}
final ViewParent parent = mView.getParent();
if (parent == null) {
return false;
}
final AccessibilityEvent event = createEvent(virtualViewId, eventType);
return ViewParentCompat.requestSendAccessibilityEvent(parent, mView, event);
}
/**
* Notifies the accessibility framework that the properties of the parent
* view have changed.
* * You must call this method after adding or removing items from the * parent view. */ public void invalidateRoot() { invalidateVirtualView(View.NO_ID); } /** * Notifies the accessibility framework that the properties of a particular * item have changed. *
* You must call this method after changing any of the properties set
* in {@link #onPopulateNodeForVirtualView}.
*
* @param virtualViewId The virtual view id to invalidate.
*/
public void invalidateVirtualView(int virtualViewId) {
sendEventForVirtualView(
virtualViewId, AccessibilityEventCompat.TYPE_WINDOW_CONTENT_CHANGED);
}
/**
* Returns the virtual view id for the currently focused item,
*
* @return A virtual view id, or {@link #INVALID_ID} if no item is
* currently focused.
*/
public int getFocusedVirtualView() {
return mFocusedVirtualViewId;
}
/**
* Sets the currently hovered item, sending hover accessibility events as
* necessary to maintain the correct state.
*
* @param virtualViewId The virtual view id for the item currently being
* hovered, or {@link #INVALID_ID} if no item is hovered within
* the parent view.
*/
private void updateHoveredVirtualView(int virtualViewId) {
if (mHoveredVirtualViewId == virtualViewId) {
return;
}
final int previousVirtualViewId = mHoveredVirtualViewId;
mHoveredVirtualViewId = virtualViewId;
// Stay consistent with framework behavior by sending ENTER/EXIT pairs
// in reverse order. This is accurate as of API 18.
sendEventForVirtualView(virtualViewId, AccessibilityEventCompat.TYPE_VIEW_HOVER_ENTER);
sendEventForVirtualView(
previousVirtualViewId, AccessibilityEventCompat.TYPE_VIEW_HOVER_EXIT);
}
/**
* Constructs and returns an {@link AccessibilityEvent} for the specified
* virtual view id, which includes the host view ({@link View#NO_ID}).
*
* @param virtualViewId The virtual view id for the item for which to
* construct an event.
* @param eventType The type of event to construct.
* @return An {@link AccessibilityEvent} populated with information about
* the specified item.
*/
private AccessibilityEvent createEvent(int virtualViewId, int eventType) {
switch (virtualViewId) {
case View.NO_ID:
return createEventForHost(eventType);
default:
return createEventForChild(virtualViewId, eventType);
}
}
/**
* Constructs and returns an {@link AccessibilityEvent} for the host node.
*
* @param eventType The type of event to construct.
* @return An {@link AccessibilityEvent} populated with information about
* the specified item.
*/
private AccessibilityEvent createEventForHost(int eventType) {
final AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
ViewCompat.onInitializeAccessibilityEvent(mView, event);
return event;
}
/**
* Constructs and returns an {@link AccessibilityEvent} populated with
* information about the specified item.
*
* @param virtualViewId The virtual view id for the item for which to
* construct an event.
* @param eventType The type of event to construct.
* @return An {@link AccessibilityEvent} populated with information about
* the specified item.
*/
private AccessibilityEvent createEventForChild(int virtualViewId, int eventType) {
final AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
event.setEnabled(true);
event.setClassName(DEFAULT_CLASS_NAME);
// Allow the client to populate the event.
onPopulateEventForVirtualView(virtualViewId, event);
// Make sure the developer is following the rules.
if (event.getText().isEmpty() && (event.getContentDescription() == null)) {
throw new RuntimeException("Callbacks must add text or a content description in "
+ "populateEventForVirtualViewId()");
}
// Don't allow the client to override these properties.
event.setPackageName(mView.getContext().getPackageName());
final AccessibilityRecordCompat record = AccessibilityEventCompat.asRecord(event);
record.setSource(mView, virtualViewId);
return event;
}
/**
* Constructs and returns an {@link AccessibilityNodeInfoCompat} for the
* specified virtual view id, which includes the host view
* ({@link View#NO_ID}).
*
* @param virtualViewId The virtual view id for the item for which to
* construct a node.
* @return An {@link AccessibilityNodeInfoCompat} populated with information
* about the specified item.
*/
private AccessibilityNodeInfoCompat createNode(int virtualViewId) {
switch (virtualViewId) {
case View.NO_ID:
return createNodeForHost();
default:
return createNodeForChild(virtualViewId);
}
}
/**
* Constructs and returns an {@link AccessibilityNodeInfoCompat} for the
* host view populated with its virtual descendants.
*
* @return An {@link AccessibilityNodeInfoCompat} for the parent node.
*/
private AccessibilityNodeInfoCompat createNodeForHost() {
final AccessibilityNodeInfoCompat node = AccessibilityNodeInfoCompat.obtain(mView);
ViewCompat.onInitializeAccessibilityNodeInfo(mView, node);
// Add the virtual descendants.
final LinkedList
* Allows the implementing class to specify most node properties, but
* overrides the following:
*
* Uses the bounds of the parent view and the parent-relative bounding
* rectangle specified by
* {@link AccessibilityNodeInfoCompat#getBoundsInParent} to automatically
* update the following properties:
*
* A virtual view will not actually take focus if
* {@link AccessibilityManager#isEnabled()} returns false,
* {@link AccessibilityManager#isTouchExplorationEnabled()} returns false,
* or the view already has accessibility focus.
*
* @param virtualViewId The id of the virtual view on which to place
* accessibility focus.
* @return Whether this virtual view actually took accessibility focus.
*/
private boolean requestAccessibilityFocus(int virtualViewId) {
if (!mManager.isEnabled()
|| !AccessibilityManagerCompat.isTouchExplorationEnabled(mManager)) {
return false;
}
// TODO: Check virtual view visibility.
if (!isAccessibilityFocused(virtualViewId)) {
mFocusedVirtualViewId = virtualViewId;
// TODO: Only invalidate virtual view bounds.
mView.invalidate();
sendEventForVirtualView(virtualViewId,
AccessibilityEventCompat.TYPE_VIEW_ACCESSIBILITY_FOCUSED);
return true;
}
return false;
}
/**
* Attempts to clear accessibility focus from a virtual view.
*
* @param virtualViewId The id of the virtual view from which to clear
* accessibility focus.
* @return Whether this virtual view actually cleared accessibility focus.
*/
private boolean clearAccessibilityFocus(int virtualViewId) {
if (isAccessibilityFocused(virtualViewId)) {
mFocusedVirtualViewId = INVALID_ID;
mView.invalidate();
sendEventForVirtualView(virtualViewId,
AccessibilityEventCompat.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED);
return true;
}
return false;
}
/**
* Provides a mapping between view-relative coordinates and logical
* items.
*
* @param x The view-relative x coordinate
* @param y The view-relative y coordinate
* @return virtual view identifier for the logical item under
* coordinates (x,y)
*/
protected abstract int getVirtualViewAt(float x, float y);
/**
* Populates a list with the view's visible items. The ordering of items
* within {@code virtualViewIds} specifies order of accessibility focus
* traversal.
*
* @param virtualViewIds The list to populate with visible items
*/
protected abstract void getVisibleVirtualViews(List
* Implementations must populate the following required fields:
*
* The helper class automatically populates the following fields with
* default values, but implementations may optionally override them:
*
* The following required fields are automatically populated by the
* helper class and may not be overridden:
*
* Implementations must populate the following required fields:
*
* The helper class automatically populates the following fields with
* default values, but implementations may optionally override them:
*
* The following required fields are automatically populated by the
* helper class and may not be overridden:
*
* Additionally, the helper class automatically handles accessibility
* focus management by adding the appropriate
* {@link AccessibilityNodeInfoCompat#ACTION_ACCESSIBILITY_FOCUS} or
* {@link AccessibilityNodeInfoCompat#ACTION_CLEAR_ACCESSIBILITY_FOCUS}
* action. Implementations must never manually add these actions.
*
* The helper class also automatically modifies parent- and
* screen-relative bounds to reflect the portion of the item visible
* within its parent.
*
* @param virtualViewId The virtual view identifier of the item for
* which to populate the node
* @param node The node to populate
*/
protected abstract void onPopulateNodeForVirtualView(
int virtualViewId, AccessibilityNodeInfoCompat node);
/**
* Performs the specified accessibility action on the item associated
* with the virtual view identifier. See
* {@link AccessibilityNodeInfoCompat#performAction(int, Bundle)} for
* more information.
*
* Implementations must handle any actions added manually in
* {@link #onPopulateNodeForVirtualView}.
*
* The helper class automatically handles focus management resulting
* from {@link AccessibilityNodeInfoCompat#ACTION_ACCESSIBILITY_FOCUS}
* and
* {@link AccessibilityNodeInfoCompat#ACTION_CLEAR_ACCESSIBILITY_FOCUS}
* actions.
*
* @param virtualViewId The virtual view identifier of the item on which
* to perform the action
* @param action The accessibility action to perform
* @param arguments (Optional) A bundle with additional arguments, or
* null
* @return true if the action was performed
*/
protected abstract boolean onPerformActionForVirtualView(
int virtualViewId, int action, Bundle arguments);
/**
* Exposes a virtual view hierarchy to the accessibility framework. Only
* used in API 16+.
*/
private class ExploreByTouchNodeProvider extends AccessibilityNodeProviderCompat {
@Override
public AccessibilityNodeInfoCompat createAccessibilityNodeInfo(int virtualViewId) {
return ExploreByTouchHelper.this.createNode(virtualViewId);
}
@Override
public boolean performAction(int virtualViewId, int action, Bundle arguments) {
return ExploreByTouchHelper.this.performAction(virtualViewId, action, arguments);
}
}
}
*
*
*
*
* @param virtualViewId The virtual view id for item for which to construct
* a node.
* @return An {@link AccessibilityNodeInfoCompat} for the specified item.
*/
private AccessibilityNodeInfoCompat createNodeForChild(int virtualViewId) {
final AccessibilityNodeInfoCompat node = AccessibilityNodeInfoCompat.obtain();
// Ensure the client has good defaults.
node.setEnabled(true);
node.setClassName(DEFAULT_CLASS_NAME);
// Allow the client to populate the node.
onPopulateNodeForVirtualView(virtualViewId, node);
// Make sure the developer is following the rules.
if ((node.getText() == null) && (node.getContentDescription() == null)) {
throw new RuntimeException("Callbacks must add text or a content description in "
+ "populateNodeForVirtualViewId()");
}
node.getBoundsInParent(mTempParentRect);
if (mTempParentRect.isEmpty()) {
throw new RuntimeException("Callbacks must set parent bounds in "
+ "populateNodeForVirtualViewId()");
}
final int actions = node.getActions();
if ((actions & AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS) != 0) {
throw new RuntimeException("Callbacks must not add ACTION_ACCESSIBILITY_FOCUS in "
+ "populateNodeForVirtualViewId()");
}
if ((actions & AccessibilityNodeInfoCompat.ACTION_CLEAR_ACCESSIBILITY_FOCUS) != 0) {
throw new RuntimeException("Callbacks must not add ACTION_CLEAR_ACCESSIBILITY_FOCUS in "
+ "populateNodeForVirtualViewId()");
}
// Don't allow the client to override these properties.
node.setPackageName(mView.getContext().getPackageName());
node.setSource(mView, virtualViewId);
node.setParent(mView);
// Manage internal accessibility focus state.
if (mFocusedVirtualViewId == virtualViewId) {
node.setAccessibilityFocused(true);
node.addAction(AccessibilityNodeInfoCompat.ACTION_CLEAR_ACCESSIBILITY_FOCUS);
} else {
node.setAccessibilityFocused(false);
node.addAction(AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS);
}
// Set the visibility based on the parent bound.
if (intersectVisibleToUser(mTempParentRect)) {
node.setVisibleToUser(true);
node.setBoundsInParent(mTempParentRect);
}
// Calculate screen-relative bound.
mView.getLocationOnScreen(mTempGlobalRect);
final int offsetX = mTempGlobalRect[0];
final int offsetY = mTempGlobalRect[1];
mTempScreenRect.set(mTempParentRect);
mTempScreenRect.offset(offsetX, offsetY);
node.setBoundsInScreen(mTempScreenRect);
return node;
}
private boolean performAction(int virtualViewId, int action, Bundle arguments) {
switch (virtualViewId) {
case View.NO_ID:
return performActionForHost(action, arguments);
default:
return performActionForChild(virtualViewId, action, arguments);
}
}
private boolean performActionForHost(int action, Bundle arguments) {
return ViewCompat.performAccessibilityAction(mView, action, arguments);
}
private boolean performActionForChild(int virtualViewId, int action, Bundle arguments) {
switch (action) {
case AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS:
case AccessibilityNodeInfoCompat.ACTION_CLEAR_ACCESSIBILITY_FOCUS:
return manageFocusForChild(virtualViewId, action, arguments);
default:
return onPerformActionForVirtualView(virtualViewId, action, arguments);
}
}
private boolean manageFocusForChild(int virtualViewId, int action, Bundle arguments) {
switch (action) {
case AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS:
return requestAccessibilityFocus(virtualViewId);
case AccessibilityNodeInfoCompat.ACTION_CLEAR_ACCESSIBILITY_FOCUS:
return clearAccessibilityFocus(virtualViewId);
default:
return false;
}
}
/**
* Computes whether the specified {@link Rect} intersects with the visible
* portion of its parent {@link View}. Modifies {@code localRect} to contain
* only the visible portion.
*
* @param localRect A rectangle in local (parent) coordinates.
* @return Whether the specified {@link Rect} is visible on the screen.
*/
private boolean intersectVisibleToUser(Rect localRect) {
// Missing or empty bounds mean this view is not visible.
if ((localRect == null) || localRect.isEmpty()) {
return false;
}
// Attached to invisible window means this view is not visible.
if (mView.getWindowVisibility() != View.VISIBLE) {
return false;
}
// An invisible predecessor means that this view is not visible.
ViewParent viewParent = mView.getParent();
while (viewParent instanceof View) {
final View view = (View) viewParent;
if ((ViewCompat.getAlpha(view) <= 0) || (view.getVisibility() != View.VISIBLE)) {
return false;
}
viewParent = view.getParent();
}
// A null parent implies the view is not visible.
if (viewParent == null) {
return false;
}
// If no portion of the parent is visible, this view is not visible.
if (!mView.getLocalVisibleRect(mTempVisibleRect)) {
return false;
}
// Check if the view intersects the visible portion of the parent.
return localRect.intersect(mTempVisibleRect);
}
/**
* Returns whether this virtual view is accessibility focused.
*
* @return True if the view is accessibility focused.
*/
private boolean isAccessibilityFocused(int virtualViewId) {
return (mFocusedVirtualViewId == virtualViewId);
}
/**
* Attempts to give accessibility focus to a virtual view.
*
*
*
*
*
*
*
* @param virtualViewId The virtual view id for the item for which to
* populate the event
* @param event The event to populate
*/
protected abstract void onPopulateEventForVirtualView(
int virtualViewId, AccessibilityEvent event);
/**
* Populates an {@link AccessibilityNodeInfoCompat} with information
* about the specified item.
*
*
*
*
*
*
*