Graphical User Interface GUI and ObjectOriented Design OOD

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Chapter 6

• Graphical User Interface (GUI) and
  Object-Oriented Design (OOD)

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Chapter Objectives

• Learn about classes used to build simple GUIs
• Learn to use GUI components Frame, Label,
  Textile, and JButton
• Become familiar with the concept of event-driven
  programming, events and event handlers
• Explore object-oriented design using GUI as an
  one example
• Learn how to identify objects, classes, and
  members of a class

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Graphical User Interface (GUI) Components

• We have already met JOptionPane from the swing
  library. It allowed us to use single variable
  text input boxes and information boxes
• Now we will look at the basic components used to
  build User interfaces which allow us to
• view inputs and outputs simultaneously in a
  single window
• To Input values of inputs in any order
• To change input values in window
• To click on buttons to initiate an action to
  produce an output

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Java GUI Components
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Graphical User Interface (GUI) Components

• GUI components
• Windows
• Labels
• Text areas
• Buttons
• A Window has a title, a content pane, additional
  GUI components can be placed on the content pane
• Labels indicate what the contents of a text box
  is, what the purpose of a button is, etc.
• A text area can be used to display and/or input
  data
• Pushing a button is associated with an action or
  event

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GUI Creation

• First create a Window with a label indicating the
  purpose of the GUI. You can specify the size of
  the window in pixels.
• Access the content pane of the window and choose
  the layout of the components
• Add the desired GUI components (labels and text
  areas)
• Add any buttons and handle the events associated
  with those buttons

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Creating a Window

• Create a Window by declaring an instance of a
  JFrame object, by using a constructor.
• The class JFrame provides various methods to
  control attributes of a window
• Attributes associated with window objects
• Title
• Width (measured in pixels)
• Height (measured in pixels)

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Methods Provided by the class Frame
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Methods Provided by the class Frame
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Two Ways to Create a Window

• First way
• Declare object of type JFrame
• Instantiate object
• Use various methods to manipulate window
• Second way
• Create subclass of JFrame containing application
  program by extending definition of class JFrame.
  JFrame is a superclass of the new subclass
• Utilizes mechanism of inheritance

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Content Pane

• Inner area of GUI window (below title bar, inside
  border)
• To access content pane
• Declare reference variable of type Container
• Use method getContentPane of class JFrame

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Methods Provided by the class Container
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class JLabel

• Class to create and modify JLabel objects
  (labels)
• A label may be aligned left, center or right
• A label may include text and/or an icon
• To create a label
• Declare and Instantiate object of type JLabel
• May modify attributes to control display of
  labels
• To add a label to a container (display the label
  in the content pane) use the method add from the
  container class

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Methods Provided by the class JLabel
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Methods Provided by the class JLabel
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class JTextField

• Used to create and modify JTextField objects
  belonging to class JTextField
• Text field may accept input or display values
• May specify length in characters of text field
• To create text field
• Declare reference variable of type JTextField
• Instantiate object
• To add a text field to a container (display the
  label in the content pane) use the method add
  from the container class

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Methods Provided by the class JTextField