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Events
An event is an action taken by the user when interacting with a
program. Some examples of user events are:
- pressing a key on the keyboard
- clicking the mouse at a particular area of the program's graphical
user interface (GUI)
- clicking a button in the GUI
- dragging the scrollbar, etc.
Buttons, text fields, choice lists, text areas, scrollbars, etc. which are
added to a GUI application (or applet) are known as GUI components. Different user actions on the various GUI
components generate different events.
Each event is represented by the relevant object. The events have to
handled appropriately based upon the program specification. The event
handling code is responsible for executing and producing the desired
results. The table below shows some of the common GUI components and the
typical event objects they generate through user actions.
Gui Component | Description | Event Object |
JButton | A common button | ActionEvent |
JCheckBox | A check box button | ItemEvent |
JRadioButton | One of a group of radio buttons | ActionEvent |
JMenuItem | A menu item | ActionEvent |
JComboBox | Selection from a choice list | ActionEvent,
ItemEvent |
JSlider | Scrollbar function | ChangeEvent |
JTextField | Plain text input field | ActionEvent |
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