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<TITLE>Listening to All Focus Changes Between Components in an Application
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
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<h3>
e613.
Listening to All Focus Changes Between Components in an Application</h3>
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.
<pre>
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 = <font color="#0066ff"><i>false</i></font>;
if (vetoFocusChange) {
throw new PropertyVetoException(<font color="#0066ff"><i>"message"</i></font>, evt);
}
}
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Related Examples
</font></td>
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e610. <a class="eglink" href="focus_FindFocus.html?l=rel">
Determining Which Component or Window Has the Focus
</a>
<br>
e611. <a class="eglink" href="focus_NoFocus.html?l=rel">
Preventing a Component from Gaining the Focus
</a>
<br>
e612. <a class="eglink" href="focus_NoFocusWindow.html?l=rel">
Preventing a Window from Gaining the Focus
</a>
<br>
e614. <a class="eglink" href="focus_FocusTravKeyComp.html?l=rel">
Setting Focus Traversal Keys in a Component
</a>
<br>
e615. <a class="eglink" href="focus_FocusTravKey.html?l=rel">
Setting Focus Traversal Keys for the Entire Application
</a>
<br>
e616. <a class="eglink" href="focus_FocusTrans.html?l=rel">
Moving the Focus to the Next or Previous Focusable Component
</a>
<br>
e617. <a class="eglink" href="focus_NextFocus.html?l=rel">
Modifying the Focus Traversal Order
</a>
<br>
e618. <a class="eglink" href="focus_InitialFocus.html?l=rel">
Setting the Initial Focused Component in a Window
</a>
<br>
e619. <a class="eglink" href="focus_FindNextFocus.html?l=rel">
Finding the Next Focusable Component
</a>
<br>
e620. <a class="eglink" href="focus_TempFocus.html?l=rel">
Determining If a Focus Lost Is Temporary or Permanent
</a>
<br>
e621. <a class="eglink" href="focus_OppositeFocus.html?l=rel">
Determining the Opposite Component of a Focus Event
</a>
<br>
e622. <a class="eglink" href="focus_ValidateFocus.html?l=rel">
Validating a JTextField When Permanently Losing the Focus
</a>
<br>
e623. <a class="eglink" href="focus_RemoveFocus.html?l=rel">
Removing the Focus from the Application
</a>
<br>
e624. <a class="eglink" href="focus_WindowFocus.html?l=rel">
Activating a Keystroke When Any Component in the Window Has Focus
</a>
<br>
e625. <a class="eglink" href="focus_ChildFocus.html?l=rel">
Activating a Keystroke When Any Child Component Has Focus
</a>
<br>
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See also:
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Colors">
Colors
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Components">
Components
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Containers">
Containers
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Cursors">
Cursors
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Drawing">
Drawing
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Events">
Events
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Frames">
Frames
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#GridBagLayout">
GridBagLayout
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Images">
Images
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Shapes">
Shapes
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Simulating%20Events">
Simulating Events
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#Text">
Text
</a>
<a class="eglink" href="/egs/java.awt/pkg.html?l=rel#The%20Screen">
The Screen
</a>
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