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e421. Listening for Changes to Preference Values in a Preference Node
A PreferenceChangeEvent is fired when a preference is added,
changed, or removed from a preference node. This event is only
guaranteed to fire if the listener and modifier are in the same
application. This event is not fired if the node is removed.
See also e422 Determining When a Preference Node Is Added or Removed.
// Retrieve the user preference node for the package java.lang
Preferences prefs = Preferences.userNodeForPackage(String.class);
// Register the listener
prefs.addPreferenceChangeListener(new PreferenceChangeListener() {
public void preferenceChange(PreferenceChangeEvent evt) {
// Get the node that changed
Preferences node = evt.getNode();
// Get the affected key.
// Note: it is not possible to tell if the key was new
// or its value was changed.
String key = evt.getKey();
// Get the new value; if the new value is null,
// the preference was removed
String newValue = evt.getNewValue();
}
});
// Add a preference
prefs.put("key", "a string");
// Modify the preference
prefs.put("key", "a new string");
// Remove the preference
prefs.remove("key");
e422.
Determining When a Preference Node Is Added or Removed
© 2002 Addison-Wesley.
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