Java Swing GUI Applications

GUI Applications

• GUI applications allow users to interact with visual controls such as buttons, labels, text boxes, tool bars, and menu items to complete tasks
• They are event-driven, meaning nothing happens until the application responds to an event such as a button press or menu selection
• Event listeners govern GUI applications by "listening" for events, and the instructions of the corresponding event method are executed when an event is detected
• Program control returns to the event listener once an event method is completed
• GUI applications are flexible, easy to use, familiar, and visually appealing

Event-Driven Behavior

• GUI applications are event-driven, with actions like button clicks or typing triggering events
• For example, a word processor waits for a click, menu selection, or text input

Swing Package

• The Swing package offers updated GUI components through Java Foundation Classes (JFC)

Creating a GUI Application

• To create a Java Swing GUI application you must create a new project
• Select the project type, and the name and location of the project package
• To add source code, right click on the source package name and select the jFrameForm
• After pressing the run project button you should select the main class

Swing Description

• Swing is a framework/API used to create GUI or window-based applications
• Swing is an advanced version of AWT (Abstract Window Toolkit) API written entirely in Java
• Unlike AWT, Java Swing provides platform-independent and lightweight components
• Swing includes 18 packages and 737 classes (JDK 1.8)

AWT vs Swing

Swing Features

• Swing is written in pure Java
• Swing is 100% portable
• Swing components are lightweight, while AWT components are heavyweight in terms of system resource utilization
• Swing components, (JComponents), are written in Java
• Swing GUI considerations are typically less complex
• Swing provides pluggable look-and-feel, allowing the choice between Java look-and-feel and the OS look-and-feel
• Swing supports mouse-less operation via the keyboard
• Swing components support tool-tips
• Swing components are JavaBeans, and support drag-and-drop in "design form" using a "GUI builder"
• Swing double-buffering and automatic repaint batching creates smoother screen repaints
• Swing uses AWT event-handling classes from the java.awt.event package
• Swing introduces JLayeredPane and JInternalFrame for creating Multiple Document Interface (MDI) applications

Commonly Used Methods

• add(Component c): Inserts a component
• setSize(int width, int height): Sets component size
• setLayout(LayoutManager m): Defines the layout manager
• setVisible(Boolean status): Changes component visibility
• setTitle(String text): Sets the component title

Swing API

• The switch to Swing is straightforward if AWT programming is familiar
• Swing component classes begin with the prefix "J"
• The JComponents should be added onto the content pane of the top-level container, where contents can be grouped and placed

Swing and AWT Components

Container Types

• JFrame: Main application window
• JDialog: Secondary pop-up window
• JApplet: Applet's display area within a browser
• JPanel: Secondary containers

Swing Controls

• JFrame: Basic container; title property for caption
• JButton: Used to start an action; text property for caption
• JLabel: Allows placement information of formatted text; text property for caption
• JTextField: Accepts one line of input from the user; text property
• JTextArea: Accepts multiple scrollable lines of input text; text property
• JCheckBox: Provides a yes/no answer; allows multiple selections
• JRadioButton: Allows selection from mutually exclusive options
• JComboBox: Allows you to select an item from a dropdown list
• JList: A list control that shows a list portion as always visible that you can make multiple selections from
• JScroll: Scroll bar that allows selection from a range of values
• JPasswordField : A component that allows the editing of a single line of text but does not show the original characters

Layout

• The JFrame can be described as having a title bar, a resizable border and a menu bar
• Layout managers describe how components are placed

Layout Managers

• FlowLayout: Components are placed in successive rows
• BorderLayout: Components are placed against the four frame borders
• CardLayout: Components are placed on top of each other
• GridLayout: Components are placed within a rectangular grid
• GridBagLayout: Components are placed with a flexible rectangular grid
• BoxLayout: Arranges components in a row or column
• SpringLayout: Arranges controls with positions defined by sprints and struts

GridBagLayout

• The top row is Row 0 and row number increases as you go down the grid
• The left column is Column 0 and column number increases as you move to the right in the grid

Building a Stopwatch Application

• Nine controls are made for a stopwatch application
• These nine controls are going to be placed in a 3x3 array, as follows:
• Text, grid coordinates
• Start Button: text start timing, (0, 0)
• Stop Button: text stop timing, (0, 1)
• Exit Button: text exit, (0, 2)
• StartLabel: Text Start time, (1, 0)
• StopLabel: Text End Time, (1,1)
• ElapsedLabel: Text Elapsed Time, (1, 2)
• startTextField: blank (2, 0)
• stopTextField: blank, (2,1)
• elapsedTextField: Blank, (2, 2)

Implementing the code

• Implement the nine declarations inside the class definition
• Establish the implementation inside the jFrameForm default constructor
• Set the positions inside the GridBagLayout grid inside the default constructor
• Declare the position of the controls in the GUI
• Make each control in the grid
• Run the pack command to finalize the implementation
• Call the event methods to allow the listeners to function
• The AWT objects primarily facilitate mouse and keyboard operation Ex: The WindowAdapter event listens for when the user runs the close command
• The control events are called after the constructor

Variables

• Variables must have a name
• Variables may have letters, numbers and underscores
• The first character must be a letter
• Java has reserved keywords
• Meaningful variable names describe the variable function
• Java variables all begin with a lower case letter with each word after the first being upper case

Data Types

• Variables store a particular type of information
• Java has as variety of data types
• Boolean, int, string, char, float, double

Data Type Ranges

• Short : -32,678 to 32,767
• Int : -2,147,483,648 to 2,147,483,647
• Long : -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
• Float: 3.14
• Double : 3.14159265359
• String Variable: List of characters in quotes Ex: “Java is fun”
• Character(char) types : Single characters in single quotes Ex: ‘a’

Scope

• Variables must have scope
• The loop level
• Method level
• Class Level

Arrays

• Data structure that stores a large number of variables under the same name
• It provides a way to store variables under the same variable name
• int[] item = new int -The array starts numbering at 0, so the number index is always one number less than what it has available. -item to item
  • item = newValue; -sum = item + item + item;
• An array can also be implemented for the GUI command as well
• Button[] myButtons = new Button;

JavaBeans

• JavaBeans are reusable, and java-based
• The JavaBeans class has commonalities with other classes such as methods, properties ,events and persistence