org.openide.util.ChangeSupport Maven / Gradle / Ivy
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package org.openide.util;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
/**
* A simple equivalent of {@link java.beans.PropertyChangeSupport} for
* {@link ChangeListener}s. This class is not serializable.
*
* @since 7.8
* @author Andrei Badea
*/
public final class ChangeSupport {
private static final Logger LOG = Logger.getLogger(ChangeSupport.class.getName());
// not private because used in unit tests
final List listeners = new CopyOnWriteArrayList();
private final Object source;
/**
* Creates a new ChangeSupport
*
* @param source the instance to be given as the source for events.
*/
public ChangeSupport(Object source) {
this.source = source;
}
/**
* Adds a ChangeListener to the listener list. The same
* listener object may be added more than once, and will be called
* as many times as it is added. If listener is null,
* no exception is thrown and no action is taken.
*
* @param listener the ChangeListener to be added.
*/
public void addChangeListener(ChangeListener listener) {
if (listener == null) {
return;
}
if (LOG.isLoggable(Level.FINE) && listeners.contains(listener)) {
LOG.log(Level.FINE, "diagnostics for #167491", new IllegalStateException("Added " + listener + " multiply"));
}
listeners.add(listener);
}
/**
* Removes a ChangeListener from the listener list.
* If listener was added more than once,
* it will be notified one less time after being removed.
* If listener is null, or was never added, no exception is
* thrown and no action is taken.
*
* @param listener the ChangeListener to be removed.
*/
public void removeChangeListener(ChangeListener listener) {
if (listener == null) {
return;
}
listeners.remove(listener);
}
/**
* Fires a change event to all registered listeners.
*/
public void fireChange() {
if (listeners.isEmpty()) {
return;
}
fireChange(new ChangeEvent(source));
}
/**
* Fires the specified ChangeEvent to all registered
* listeners. If event is null, no exception is thrown
* and no action is taken.
*
* @param event the ChangeEvent to be fired.
*/
private void fireChange(ChangeEvent event) {
assert event != null;
for (ChangeListener listener : listeners) {
try {
listener.stateChanged(event);
} catch (RuntimeException x) {
Exceptions.printStackTrace(x);
}
}
}
/**
* Checks if there are any listeners registered to thisChangeSupport.
*
* @return true if there are one or more listeners for the given property,
* false otherwise.
*/
public boolean hasListeners() {
return !listeners.isEmpty();
}
}