• Understand computer graphics in general.
  • Understand Java's implementation of graphics.
  • Understand how to draw basic shapes and text on a window.
  • Understand the Graphics class
  • Understand how to override paint and paintComponent methods.
  • Understand how to process several graphics events.
  • Understand Swing components such as Jlabel, JButton, JCheckBox, JTextField, etc.
  • Graphics

    Programming graphics can be fun, but it involves a lot of Java concepts, some of which complex. You have to take your time an think when programming Java graphics. Our goal for graphics is not to become an expert, but rather to achieve a general understanding, mimick a few programs, and create several simple programs. There are no test questions on graphics. I think everyone will enjoy using the Netbeand GUI building. I hope some interested students pursue graphics in more depth on their own - perhaps on the final project where students choose their own. Most likely the information in this module will have to be augmented with in class. discussions

    The Graphics Code Pattern is as follows.

    The Graphics pattern shows conceptually what is happening. As we study graphics, you will discover that you do not code a loop to process events. You simply write methods that are called by the underlying Java graphics libraries, which have the loop structure.

    The approach for studying graphics is to first study drawing in windows before studying events.

    • Part 1 - Output - Drawing shapes and text

      • Create a program that has window without content.
      • Create a program that has a window and draws basic content with low-level JFrame graphics methods.
      • Create a program that has a window and draws basic content with low-level JPanel graphics methods.
      • Create a program that has multiple components, such as buttons, labels, and text fields.
      • Examine several sample programs in Graphics Drawing Code.
    • Part 2 - Events and Input

      • Create a Hello World program that processes one event - mouse click on a button.
      • Examine several sample programs in Graphics Events Code.

    Graphics and the Wirth Pattern

    Modern day programs on laptops, phones, desktops, and tablets use a graphical user interface (GUI) to interact with users. A GUI provides input to programs from components such as text entry fields for typing input, buttons for selecting, and pull down menus for selecting. A GUI provides output from programs via components such as text fields, pictures, animations, and figures. A program with a GUI consists of algorithms and data structures that transform input into output. The difference is that input and output is via the GUI instead of the terminal. These concepts can be viewed in the Wirth pattern from Primitive Types.

    Java Graphics History

    • The Abstract Window Toolkit (AWT) was the original Java graphics. All of the AWT types are in the java.awt package and can be imported via

      import java.awt.*;
      
    • Swing is the second incarnation of Java graphics. Swing is built on top of AWT - they are used in conjunction. All of the Swing types are in the javax.swing package and can be imported via

      import javax.swing.*;
      
    • Java has recently introduced JavaFX, which is intended to replace Swing.

    We will use AWT and Swing.

    PowerBall Code in One File Review

    In Instance and Static we learned how to merge a class definition (with instance variables/methods) and a main method into one .java file. Many of our graphics programs use this technique. Recall the following figure to help prepare for creating a graphics program.

    Power Ball Merged

    Graphics and Objects

    Object-oriented programming started with graphics programming. You will discover many graphics classes in the java.awt and java.swing packages. Some of the many classes are the following.

    • JFrame is a window.
    • JButton is a button that can be selected with a mouse (or trackpad) click.
    • JTextArea is a box into which text may be typed.
    • JComboBox is a popup menu that allows mutual exclusion selection of one from several.
    • JLabel is a text label.
    • JTextField is a small area into which text may be typed.

    To demonstrate the subclasses, consider a JButton, which extends an AbstractButton, which extends JComponent, and so on. The entire class hierarchy is the following.

    • java.lang.Object
      • java.awt.Component
        • java.awt.Container
          • javax.swing.JComponent
            • javax.swing.AbstractButton
              • javax.swing.JButton

    Graphics Lab

    The graphics overview lab is Graphics.

    Sites with Java Graphics

    David Eck’s Book

    David Eck’s book has graphics code sprinkled throughout as examples. The following are some sections/chapters dedicated to graphics.

    Java Custom Graphics Tutorial

    Custom Graphics is a nice web-site on manipulating Java graphics on a Graphics context.

    Loyal Marymont

    Basic Java Graphics from Loyola Marymont University, Los Angeles

    Tags: graphics