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An Introduction to Graphical User Interface (GUI) Technology
With Examples in Java


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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The Building Blocks
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  • Components/Widgets:
    • The parts of a GUI (e.g., buttons, sliders, text fields)
  • Containers:
    • "Screen real estate" that contains components/widgets
Some Top-Level Containers (i.e., Realizations of JRootPaneContainer javax.swing.JRootPaneContainer )
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  • JFrame javax.swing.JFrame :
    • A main "window" most commonly used by an application
  • JApplet javax.swing.JApplet :
    • Most commonly a portion of a WWW page (displayed in a browser)
Creating a JFrame
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javaexamples/gui/JFrameDriver.java
 
Working with Top-Level Containers
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  • The JRootPane javax.swing.JRootPane :
    • JRootPaneContainer objects have a JRootPane that manages layers (if any), menus (if any), and content
    • Should not be used
  • The Content Pane:
    • A JRootPane has a Container java.awt.Container called the content pane that manages all of the usable "screen real estate"
    • Accessed using the getContentPane() method
Some GUI Components
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  • JButton javax.swing.JButton :
    • images/button_windows.gif
  • JCheckBox javax.swing.JCheckBox /JRadioButton javax.swing.JRadioButton :
    • images/radiobutton_windows.gif
  • JTextField javax.swing.JTextField /JTextArea javax.swing.JTextArea :
    • images/textfield_windows.gif
  • JComboBox javax.swing.JComboBox :
    • images/combobox_windows.gif
  • JSlider javax.swing.JSlider :
    • images/slider_windows.gif
GUI Layout
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  • Organizing GUI components
  • Grouping GUI components
  • Positioning GUI components
Absolute Layout
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The "Graph Paper" Approach

images/layout_absolute1.gif
Absolute Layout in Java
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The null LayoutManager java.awt.LayoutManager

javaexamples/layout/NullLayoutFrame.java
 
Other Approaches to Layout (Not Considered Here)
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  • Relative Layout:
    • Components are positioned relative to each other, rather than an absolute position
  • Template Layout:
    • Divide the container into sections and place one component in each section
  • Hierarchical Template Layout:
    • Subdivide the sections in a template layout
  • Constrained Template Layout:
    • Add constraints (e.g., doesn't expand) to sections of a template
Responding to GUI Components
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  1. Determine what events the component generates
  2. Identify the interfaces that needs to be implemented
  3. Create a class that implements that interfaces
  4. Add "application logic" to the appropriate methods
Example: Responding to JButton Objects
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  • The Event(s):
    • ActionEvent
  • The Interface(s):
    • ActionListener
  • The Method(s)/Message(s):
    • void actionPerformed(ActionEvent event)
Example: Responding to JButton Objects (cont.)
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javaexamples/usinggui/ButtonFrame.java
 
There's Always More to Learn
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