e609. Listening to All Focus Changes Between Components in an Application
2024-10-10 21:28:31
To listen to focus change events between components, install a listener with the keyboard focus manager. If you need the ability to veto (reject) a focus change, install a vetoable listener with the keyboard focus manager.
KeyboardFocusManager.getCurrentKeyboardFocusManager()
.addPropertyChangeListener(new FocusChangeListener());
KeyboardFocusManager.getCurrentKeyboardFocusManager()
.addVetoableChangeListener(new FocusVetoableChangeListener()); class FocusChangeListener implements PropertyChangeListener {
public void propertyChange(PropertyChangeEvent evt) {
Component oldComp = (Component)evt.getOldValue();
Component newComp = (Component)evt.getNewValue(); if ("focusOwner".equals(evt.getPropertyName())) {
if (oldComp == null) {
// the newComp component gained the focus
} else {
// the oldComp component lost the focus
}
} else if ("focusedWindow".equals(evt.getPropertyName())) {
if (oldComp == null) {
// the newComp window gained the focus
} else {
// the oldComp window lost the focus
}
}
}
} class FocusVetoableChangeListener implements VetoableChangeListener {
public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
Component oldComp = (Component)evt.getOldValue();
Component newComp = (Component)evt.getNewValue(); if ("focusOwner".equals(evt.getPropertyName())) {
if (oldComp == null) {
// the newComp component will gain the focus
} else {
// the oldComp component will lose the focus
}
} else if ("focusedWindow".equals(evt.getPropertyName())) {
if (oldComp == null) {
// the newComp window will gain the focus
} else {
// the oldComp window will lose the focus
}
} boolean vetoFocusChange = false;
if (vetoFocusChange) {
throw new PropertyVetoException("message", evt);
}
}
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