Introduction Events Event Handling Details Eg. Two buttons Eg. One slider Eg. Three sliders Eg. Mouse drag Eg. Mouse move Eg. Mouse drag and move Assignments

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