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JAVA APPLET
Introduction to Events
All the AWT components have been changed to include addXXXListener( )
and removeXXXListener( ) methods so that the appropriate types
of listeners can be added and removed from each component. You’ll notice
that the "XXX" in each case also represents the argument
for the method, for example, addFooListener(FooListener fl).
The following table includes the
associated events, listeners, methods, and the components that support
those particular events by providing the addXXXListener( ) and
removeXXXListener( ) methods.
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Event, listener interface and add- and
remove-methods
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Components supporting this event
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ActionEvent
ActionListener
addActionListener( )
removeActionListener( )
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Button, List,
TextField, MenuItem, and its derivatives including CheckboxMenuItem,
Menu, and PopupMenu
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AdjustmentEvent
AdjustmentListener
addAdjustmentListener( )
removeAdjustmentListener( )
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Scrollbar
Anything you create that implements the Adjustable
interface
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ComponentEvent
ComponentListener
addComponentListener( )
removeComponentListener( )
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Component and its
derivatives, including Button, Canvas, Checkbox,
Choice, Container, Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, Frame, Label,
List, Scrollbar, TextArea, and TextField
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ContainerEvent
ContainerListener
addContainerListener( )
removeContainerListener( )
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Container and its
derivatives, including Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, and Frame
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FocusEvent
FocusListener
addFocusListener( )
removeFocusListener( )
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Component and its
derivatives, including Button, Canvas, Checkbox,
Choice, Container, Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, Frame Label,
List, Scrollbar, TextArea, and TextField
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KeyEvent
KeyListener
addKeyListener( )
removeKeyListener( )
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Component and its
derivatives, including Button, Canvas, Checkbox,
Choice, Container, Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, Frame, Label,
List, Scrollbar, TextArea, and TextField
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MouseEvent (for both
clicks and motion)
MouseListener
addMouseListener( )
removeMouseListener( )
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Component and its
derivatives, including Button, Canvas, Checkbox,
Choice, Container, Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, Frame, Label,
List, Scrollbar, TextArea, and TextField
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MouseEvent (for both
clicks and motion)
MouseMotionListener
addMouseMotionListener( )
removeMouseMotionListener( )
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Component and its
derivatives, including Button, Canvas, Checkbox,
Choice, Container, Panel, Applet, ScrollPane,
Window, Dialog, FileDialog, Frame, Label,
List, Scrollbar, TextArea, and TextField
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WindowEvent
WindowListener
addWindowListener( )
removeWindowListener( )
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Window and its
derivatives, including Dialog, FileDialog, and Frame
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ItemEvent
ItemListener
addItemListener( )
removeItemListener( )
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Checkbox, CheckboxMenuItem,
Choice, List, and anything that implements the ItemSelectable
interface
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TextEvent
TextListener
addTextListener( )
removeTextListener( )
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Anything derived from TextComponent,
including TextArea and TextField
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You can see that each type of
component supports only certain types of events. It’s helpful to see the
events supported by each component, as shown in the following table:
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Component type
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Events supported by this component
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Adjustable
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AdjustmentEvent
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Applet
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ContainerEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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Button
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ActionEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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Canvas
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FocusEvent, KeyEvent, MouseEvent, ComponentEvent
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Checkbox
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ItemEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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CheckboxMenuItem
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ActionEvent, ItemEvent
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Choice
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ItemEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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Component
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FocusEvent, KeyEvent, MouseEvent, ComponentEvent
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Container
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ContainerEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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Dialog
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ContainerEvent, WindowEvent, FocusEvent,
KeyEvent, MouseEvent, ComponentEvent
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FileDialog
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ContainerEvent, WindowEvent, FocusEvent,
KeyEvent, MouseEvent, ComponentEvent
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Frame
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ContainerEvent, WindowEvent, FocusEvent,
KeyEvent, MouseEvent, ComponentEvent
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Label
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FocusEvent, KeyEvent, MouseEvent, ComponentEvent
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List
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ActionEvent, FocusEvent, KeyEvent, MouseEvent,
ItemEvent, ComponentEvent
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Menu
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ActionEvent
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MenuItem
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ActionEvent
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Panel
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ContainerEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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PopupMenu
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ActionEvent
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Scrollbar
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AdjustmentEvent, FocusEvent, KeyEvent,
MouseEvent, ComponentEvent
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ScrollPane
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ContainerEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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TextArea
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TextEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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TextComponent
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TextEvent, FocusEvent, KeyEvent, MouseEvent,
ComponentEvent
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TextField
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ActionEvent, TextEvent, FocusEvent, KeyEvent,
MouseEvent, ComponentEvent
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Window
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ContainerEvent, WindowEvent, FocusEvent,
KeyEvent, MouseEvent, ComponentEvent
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Once you know which events a
particular component supports, you don’t need to look anything up to
react to that event. You simply:
- Take the name of the event class and remove the
word "Event." Add the word "Listener"
to what remains. This is the listener interface you need to
implement in your inner class.
- Implement the interface above and write out the
methods for the events you want to capture. For example, you might
be looking for mouse movements, so you write code for the mouseMoved( )
method of the MouseMotionListener interface. (You must
implement the other methods, of course, but there’s a shortcut for
that which you’ll see soon.)
- Create an object of the listener class in step 2.
Register it with your component with the method produced by
prefixing "add" to your listener name. For example,
addMouseMotionListener( ).
To finish what you need to know,
here are the listener interfaces:
Listener interface
w/ adapter
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Methods in interface
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ActionListener
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actionPerformed(ActionEvent)
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AdjustmentListener
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adjustmentValueChanged(
AdjustmentEvent)
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ComponentListener
ComponentAdapter
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componentHidden(ComponentEvent)
componentShown(ComponentEvent)
componentMoved(ComponentEvent)
componentResized(ComponentEvent)
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ContainerListener
ContainerAdapter
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componentAdded(ContainerEvent)
componentRemoved(ContainerEvent)
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FocusListener
FocusAdapter
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focusGained(FocusEvent)
focusLost(FocusEvent)
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KeyListener
KeyAdapter
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keyPressed(KeyEvent)
keyReleased(KeyEvent)
keyTyped(KeyEvent)
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MouseListener
MouseAdapter
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mouseClicked(MouseEvent)
mouseEntered(MouseEvent)
mouseExited(MouseEvent)
mousePressed(MouseEvent)
mouseReleased(MouseEvent)
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MouseMotionListener
MouseMotionAdapter
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mouseDragged(MouseEvent)
mouseMoved(MouseEvent)
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WindowListener
WindowAdapter
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windowOpened(WindowEvent)
windowClosing(WindowEvent)
windowClosed(WindowEvent)
windowActivated(WindowEvent)
windowDeactivated(WindowEvent)
windowIconified(WindowEvent)
windowDeiconified(WindowEvent)
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ItemListener
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itemStateChanged(ItemEvent)
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TextListener
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textValueChanged(TextEvent)
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