/**
* Because there may be many AppContexts, and we can't be sure where this EmbeddedFrame is first
* created or shown, we can't automatically determine the correct KeyboardFocusManager to attach
* to as KeyEventDispatcher. Those who want to use the functionality of traversing out of the
* EmbeddedFrame must call this method on the Applet's AppContext. After that, all the changes can
* be handled automatically, including possible replacement of KeyboardFocusManager.
*/
public void registerListeners() {
if (appletKFM != null) {
removeTraversingOutListeners(appletKFM);
}
appletKFM = KeyboardFocusManager.getCurrentKeyboardFocusManager();
if (isVisible()) {
addTraversingOutListeners(appletKFM);
}
}
/**
* Needed to track which KeyboardFocusManager is current. We want to avoid memory leaks, so when
* KFM stops being current, we remove ourselves as listeners.
*/
public void propertyChange(PropertyChangeEvent evt) {
// We don't handle any other properties. Skip it.
if (!evt.getPropertyName().equals("managingFocus")) {
return;
}
// We only do it if it stops being current. Technically, we should
// never get an event about KFM starting being current.
if (evt.getNewValue() == Boolean.TRUE) {
return;
}
// should be the same as appletKFM
removeTraversingOutListeners((KeyboardFocusManager) evt.getSource());
appletKFM = KeyboardFocusManager.getCurrentKeyboardFocusManager();
if (isVisible()) {
addTraversingOutListeners(appletKFM);
}
}
/**
* Needed to avoid memory leak: we register this EmbeddedFrame as a listener with
* KeyboardFocusManager of applet's AppContext. We don't want the KFM to keep reference to our
* EmbeddedFrame forever if the Frame is no longer in use, so we add listeners in show() and
* remove them in hide().
*/
public void hide() {
if (appletKFM != null) {
removeTraversingOutListeners(appletKFM);
}
super.hide();
}