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lecture21 - PIC 20A Lecture 21: Event Handling Events an...

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PIC 20A Lecture 21: Event Handling
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Events • an event is an interaction of the user with a GUI component • events are modeled in Java by event objects Examples – pressing a button ( ActionEvent ) – selecting a menu item ( ActionEvent ) – pressing a key ( KeyEvent ) – setting the focus on a component ( FocusEvent ) – clicking the mouse ( MouseEvent )
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Events Store Information • every event has a source - the GUI component with which the user interacted • to access a reference to the source, use the getSource() method of the event object
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Responding to Events event handler - method which is called automatically in response to an event ActionEvent handler public void actionPerformed(ActionEvent e) must be defined if your class implements the event-listener interface ActionListener
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event-listener interface ? • an interface containing abstract event handler method declarations for a particular event type eg ActionListener (ActionEvent) MouseListener (MouseEvent) MouseMotionListener (MouseMotionEvent) MouseWheelListener (MouseWheelEvent) KeyListener (KeyEvent) FocusListener (FocusEvent) ItemListener (ItemEvent)
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lecture21 - PIC 20A Lecture 21: Event Handling Events an...

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