{@code AccessibilityEventMonitor} implements a PropertyChange listener - * on every UI object that implements interface {@code Accessible} in the Java - * Virtual Machine. The events captured by these listeners are made available - * through listeners supported by {@code AccessibilityEventMonitor}. - * With this, all the individual events on each of the UI object - * instances are funneled into one set of PropertyChange listeners. - *
This class depends upon {@link EventQueueMonitor}, which provides the base - * level support for capturing the top-level containers as they are created. - * - */ - -@jdk.Exported -public class AccessibilityEventMonitor { - - // listeners - /** - * The current list of registered {@link java.beans.PropertyChangeListener - * PropertyChangeListener} classes. - * - * @see #addPropertyChangeListener - * @see #removePropertyChangeListener - */ - static protected final AccessibilityListenerList listenerList = - new AccessibilityListenerList(); - - - /** - * The actual listener that is installed on the component instances. - * This listener calls the other registered listeners when an event - * occurs. By doing things this way, the actual number of listeners - * installed on a component instance is drastically reduced. - */ - static protected final AccessibilityEventListener accessibilityListener = - new AccessibilityEventListener(); - - /** - * Adds the specified listener to receive all PropertyChange events on - * each UI object instance in the Java Virtual Machine as they occur. - *
Note: This listener is automatically added to all component - * instances created after this method is called. In addition, it - * is only added to UI object instances that support this listener type. - * - * @param l the listener to add - * - * @see #removePropertyChangeListener - */ - static public void addPropertyChangeListener(PropertyChangeListener l) { - if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) { - accessibilityListener.installListeners(); - } - listenerList.add(PropertyChangeListener.class, l); - } - - /** - * Removes the specified listener so it no longer receives PropertyChange - * events when they occur. - * @see #addPropertyChangeListener - * @param l the listener to remove - */ - static public void removePropertyChangeListener(PropertyChangeListener l) { - listenerList.remove(PropertyChangeListener.class, l); - if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) { - accessibilityListener.removeListeners(); - } - } - - - /** - * AccessibilityEventListener is the class that does all the work for - * AccessibilityEventMonitor. It is not intended for use by any other - * class except AccessibilityEventMonitor. - * - */ - - static class AccessibilityEventListener implements TopLevelWindowListener, - PropertyChangeListener { - - /** - * Create a new instance of this class and install it on each component - * instance in the virtual machine that supports any of the currently - * registered listeners in AccessibilityEventMonitor. Also registers - * itself as a TopLevelWindowListener with EventQueueMonitor so it can - * automatically add new listeners to new components. - * @see EventQueueMonitor - * @see AccessibilityEventMonitor - */ - public AccessibilityEventListener() { - EventQueueMonitor.addTopLevelWindowListener(this); - } - - /** - * Installs PropertyChange listeners on all Accessible objects based - * upon the current topLevelWindows cached by EventQueueMonitor. - * @see EventQueueMonitor - * @see AWTEventMonitor - */ - protected void installListeners() { - Window topLevelWindows[] = EventQueueMonitor.getTopLevelWindows(); - if (topLevelWindows != null) { - for (int i = 0; i < topLevelWindows.length; i++) { - if (topLevelWindows[i] instanceof Accessible) { - installListeners((Accessible) topLevelWindows[i]); - } - } - } - } - - /** - * Installs PropertyChange listeners to the Accessible object, and it's - * children (so long as the object isn't of TRANSIENT state). - * @param a the Accessible object to add listeners to - */ - protected void installListeners(Accessible a) { - installListeners(a.getAccessibleContext()); - } - - /** - * Installs PropertyChange listeners to the AccessibleContext object, - * and it's * children (so long as the object isn't of TRANSIENT state). - * @param a the Accessible object to add listeners to - */ - private void installListeners(AccessibleContext ac) { - - if (ac != null) { - AccessibleStateSet states = ac.getAccessibleStateSet(); - if (!states.contains(AccessibleState.TRANSIENT)) { - ac.addPropertyChangeListener(this); - /* - * Don't add listeners to transient children. Components - * with transient children should return an AccessibleStateSet - * containing AccessibleState.MANAGES_DESCENDANTS. Components - * may not explicitly return the MANAGES_DESCENDANTS state. - * In this case, don't add listeners to the children of - * lists, tables and trees. - */ - AccessibleStateSet set = ac.getAccessibleStateSet(); - if (set.contains(_AccessibleState.MANAGES_DESCENDANTS)) { - return; - } - AccessibleRole role = ac.getAccessibleRole(); - if (role == AccessibleRole.LIST || - role == AccessibleRole.TREE) { - return; - } - if (role == AccessibleRole.TABLE) { - // handle Oracle tables containing tables - Accessible child = ac.getAccessibleChild(0); - if (child != null) { - AccessibleContext ac2 = child.getAccessibleContext(); - if (ac2 != null) { - role = ac2.getAccessibleRole(); - if (role != null && role != AccessibleRole.TABLE) { - return; - } - } - } - } - int count = ac.getAccessibleChildrenCount(); - for (int i = 0; i < count; i++) { - Accessible child = ac.getAccessibleChild(i); - if (child != null) { - installListeners(child); - } - } - } - } - } - - /** - * Removes PropertyChange listeners on all Accessible objects based - * upon the topLevelWindows cached by EventQueueMonitor. - * @param eventID the event ID - * @see EventID - */ - protected void removeListeners() { - Window topLevelWindows[] = EventQueueMonitor.getTopLevelWindows(); - if (topLevelWindows != null) { - for (int i = 0; i < topLevelWindows.length; i++) { - if (topLevelWindows[i] instanceof Accessible) { - removeListeners((Accessible) topLevelWindows[i]); - } - } - } - } - - /** - * Removes PropertyChange listeners for the given Accessible object, - * it's children (so long as the object isn't of TRANSIENT state). - * @param a the Accessible object to remove listeners from - */ - protected void removeListeners(Accessible a) { - removeListeners(a.getAccessibleContext()); - } - - /** - * Removes PropertyChange listeners for the given AccessibleContext - * object, it's children (so long as the object isn't of TRANSIENT - * state). - * @param a the Accessible object to remove listeners from - */ - private void removeListeners(AccessibleContext ac) { - - - if (ac != null) { - // Listeners are not added to transient components. - AccessibleStateSet states = ac.getAccessibleStateSet(); - if (!states.contains(AccessibleState.TRANSIENT)) { - ac.removePropertyChangeListener(this); - /* - * Listeners are not added to transient children. Components - * with transient children should return an AccessibleStateSet - * containing AccessibleState.MANAGES_DESCENDANTS. Components - * may not explicitly return the MANAGES_DESCENDANTS state. - * In this case, don't remove listeners from the children of - * lists, tables and trees. - */ - if (states.contains(_AccessibleState.MANAGES_DESCENDANTS)) { - return; - } - AccessibleRole role = ac.getAccessibleRole(); - if (role == AccessibleRole.LIST || - role == AccessibleRole.TABLE || - role == AccessibleRole.TREE) { - return; - } - int count = ac.getAccessibleChildrenCount(); - for (int i = 0; i < count; i++) { - Accessible child = ac.getAccessibleChild(i); - if (child != null) { - removeListeners(child); - } - } - } - } - } - - /********************************************************************/ - /* */ - /* Listener Interface Methods */ - /* */ - /********************************************************************/ - - /* TopLevelWindow Methods ***************************************/ - - /** - * Called when top level window is created. - * @see EventQueueMonitor - * @see EventQueueMonitor#addTopLevelWindowListener - */ - public void topLevelWindowCreated(Window w) { - if (w instanceof Accessible) { - installListeners((Accessible) w); - } - } - - /** - * Called when top level window is destroyed. - * @see EventQueueMonitor - * @see EventQueueMonitor#addTopLevelWindowListener - */ - public void topLevelWindowDestroyed(Window w) { - if (w instanceof Accessible) { - removeListeners((Accessible) w); - } - } - - - /* PropertyChangeListener Methods **************************************/ - - public void propertyChange(PropertyChangeEvent e) { - // propogate the event - Object[] listeners = - AccessibilityEventMonitor.listenerList.getListenerList(); - for (int i = listeners.length-2; i>=0; i-=2) { - if (listeners[i]==PropertyChangeListener.class) { - ((PropertyChangeListener)listeners[i+1]).propertyChange(e); - } - } - - // handle childbirth/death - String name = e.getPropertyName(); - if (name.compareTo(AccessibleContext.ACCESSIBLE_CHILD_PROPERTY) == 0) { - Object oldValue = e.getOldValue(); - Object newValue = e.getNewValue(); - - if ((oldValue == null) ^ (newValue == null)) { // one null, not both - if (oldValue != null) { - // this Accessible is a child that's going away - if (oldValue instanceof Accessible) { - Accessible a = (Accessible) oldValue; - removeListeners(a.getAccessibleContext()); - } else if (oldValue instanceof AccessibleContext) { - removeListeners((AccessibleContext) oldValue); - } - } else if (newValue != null) { - // this Accessible is a child was just born - if (newValue instanceof Accessible) { - Accessible a = (Accessible) newValue; - installListeners(a.getAccessibleContext()); - } else if (newValue instanceof AccessibleContext) { - installListeners((AccessibleContext) newValue); - } - } - } else { - System.out.println("ERROR in usage of PropertyChangeEvents for: " + e.toString()); - } - } - } - } -} - -/* - * workaround for no public AccessibleState constructor - */ -class _AccessibleState extends AccessibleState { - /** - * Indicates this object is responsible for managing its - * subcomponents. This is typically used for trees and tables - * that have a large number of subcomponents and where the - * objects are created only when needed and otherwise remain virtual. - * The application should not manage the subcomponents directly. - */ - public static final _AccessibleState MANAGES_DESCENDANTS - = new _AccessibleState ("managesDescendants"); - - /** - * Creates a new AccessibleState using the given locale independent key. - * This should not be a public method. Instead, it is used to create - * the constants in this file to make it a strongly typed enumeration. - * Subclasses of this class should enforce similar policy. - *
- * The key String should be a locale independent key for the state. - * It is not intended to be used as the actual String to display - * to the user. To get the localized string, use toDisplayString. - * - * @param key the locale independent name of the state. - * @see AccessibleBundle#toDisplayString - */ - protected _AccessibleState(String key) { - super(key); - } -}