Outline

1
Outline

• Swing and AWT
• Swing basics
• Layout Managers
• Stand alone GUI applications
• Applets
• Misc

2
AWT and Swing

• Basic GUI elements are implemented in two
  packages java.awt, and javax.swing
• Abstract Windowing Toolkit (AWT)
• Set of GUI components introduced in JDK 1.0
• Depends on native GUI
• Swing
• Largely supersedes AWT, but depends of AWT
  classes
• Implemented in Java
• Applications look exactly the same on different
  platforms
• Not as fast as AWT
• Pluggable look-and-feel

3
Swing

• Stand alone applications and applets
• Various components
• Buttons
• Menus
• Dialogs
• Trees
• Progress bars
• Sliders
• Split panes
• Tabbed panes
• Etc. etc. etc.

4
Inheritance hierarchy JLabel
java.lang.Object
java.awt.Component
java.awt.Container
javax.swing.JComponent
javax.swing.JLabel

• Component defines basic properties of
  components
• Container a component that can contain other
  components

5
Containment hierarchy

• Top level container
• Each GUI has a container at the top of the
  containment hierarchy
• Applications JFrame or JDialog
• Applets JApplet
• Intermediate-level containers
• Contain other components and/or containers
• E.g. JScrollPane or JSplitPane
• Atomic components
• E.g. JButton
• Other
• E.g. JTree

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Containment hierarchy example

• JFrame

JPanel
JButton
JButton
JLabel
7
Containment hierarchy how?

• Create components
• Add components to a container using one of the
  various forms of the add method
• Example
• JPanel buttonPanel new JPanel()
• JButton helpButton new JButton(Help)
• JButton quitButton new JButton(Quit)
• JLabel titleLabel new JLabel(GUI
  Demo)buttonPanel.add(helpButton)
• buttonPanel.add(quitButton)
• buttonPanel.add(titleLabel)

8
Layout Managers

• Determine the size and position of the components
  within a container
• Handle automatic resizing of the container
• Add components with the containers layout
  manager in mind
• FlowLayout
• BorderLayout
• GridLayout
• GridBagLayout (advanced)
• Others

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Flow Layout

• Places things one after another, in order added
  to the container
• Container c getContentPane()
• c.setLayout(new FlowLayout())
• c.add(new JButton(OK))
• c.add(new JButton(Open))
• c.add(new JButton(Close))

10
Border Layout

• Places along border, or in center
• Container c getContentPane()
• c.setLayout(new BorderLayout())
• c.add("North", new Button("North"))
• c.add("South", new Button("South"))
• c.add("East", new Button("East"))
• c.add("West", new Button("West"))
• c.add("Center", new Button("Center"))

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Grid Layout

• Lays out in a user-specified grid
• Container c getContentPane()
• c.setLayout(new GridLayout(3,2))
• c.add(new Button("1"))
• c.add(new Button("2"))
• c.add(new Button("3"))
• c.add(new Button("4"))
  
• c.add(new Button("5"))
• c.add(new Button("6"))

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Swing Applications

• Set up a top level container (either JFrame or
  JDialog)
• Set up components to comprise your GUI
• Add components to containers
• Handle events (next class)

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Swing Applications (Example)

• import javax.swing.
• import java.awt.
• public class SimpleSwing extends JFrame
• public SimpleSwing()
• // Get, configure, and populate the root
  container
• Container container this.getContentPane()
• container.setLayout(new BorderLayout())
• container.add("North", createCoordPanel())
• container.add("South", createButtonPanel())
• container.add("West", createColorShapePanel())
  
• public static void main(String args)
• SimpleSwing frame new SimpleSwing()

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Swing Applications (Example)
/ Create and populate the co-ordinate panel.
/ protected JPanel createCoordPanel()
// Create the co-ordinate panel JPanel
coordPanel new JPanel() // Populate it
with labels and text fields
coordPanel.add(new JLabel("x1", Label.LEFT))
JTextField textX1 new JTextField(2)
coordPanel.add(textX1) coordPanel.add(new
JLabel("y1", Label.LEFT)) JTextField textY1
new JTextField(2) coordPanel.add(textY1)
coordPanel.add(new JLabel("x2", Label.LEFT))
JTextField textX2 new JTextField(2)
coordPanel.add(textX2) coordPanel.add(new
JLabel("y2", Label.LEFT)) JTextField textY2
new JTextField(2) coordPanel.add(textY2)
return coordPanel

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Swing Applications (Example)

• / Creates the panel containing the "Draw"
  button /
• protected JPanel createButtonPanel()
• // Create the button panel
• JPanel buttonPanel new JPanel()
• // Create the draw button
• JButton drawButton new JButton("Draw")
• // Add the button to the panel
• buttonPanel.add(drawButton)
• return buttonPanel

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Swing Applications (Example)

/ Creates the color/shape panel /
protected JPanel createColorShapePanel()
// Create and configure the panel JPanel
colorShapePanel new JPanel()
colorShapePanel.setLayout(new BorderLayout())
// Create and populate the two ComboBoxes
String colors "Red", "Yellow", "Green",
"Blue", "Black", "White" JComboBox
colorList new JComboBox(colors)
colorList.setSelectedIndex(0) String
shapes "Circle", "Rectangle", "Line"
JComboBox shapeList new JComboBox(shapes)
shapeList.setSelectedIndex(0) // Add them
to the panel colorShapePanel.add("North",
colorList) colorShapePanel.add("South",
shapeList) return colorShapePanel
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Swing Applications (Example)

• This example wont interact with the user
• Handling interaction-next class

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Swing Applets

• Top level container is JApplet
• An interface to allow small Java programs run in
  a browser
• init() called when an applet is first loaded
• start() whenever the page the applet is on is
  viewed or revisited
• stop() whenever the user leaves the page
• destroy() called after stop() when browser is
  shut down
• No need to define a main method

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Swing Applets (Example)

• import java.awt.
• import javax.swing.
• public class MyApplet extends JApplet
• public void init()
• Container pane getContentPane()
• JLabel label new JLabel("Hello Swing
  applet world!")
• label.setHorizontalAlignment(JLabel.CENTER
  )
• appletPane.add(label, BorderLayout.CENTER)
  

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Viewing Applets

• Requires some special HTML code
• HTML - generic language of web browsers
• lthtmlgt
• ltapplet codeMyApplet.class width300
  height100gt
• lt/appletgt
• lt/htmlgt
• Save in file MyAppletTest.html
• Use Appletviewer to view
• appletviewer MyAppletTest.html

To put in an existing page, only these two middle
lines are needed
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Misc Components Color and Font

• Color
• jcomponent.setBackground(Color r)
• jcomponent.setForeground(Color r)
• Color.yellow, Color.red, etc.
• Font
• Font f new Font(Serif, Font.BOLD, 14)
• jcomponent.setFont(f)

22
Misc Custom Painting

• The Graphics Class
• Controls how information is drawn
• Every container or component has a graphics
  context (instance of Graphics) representing its
  on-screen real estate
• To update screen, paintComponent is called and
  passed the Graphics object overriding this in a
  JComponent subclass lets you create custom widgets

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Misc Custom Painting (contd)

• Some methods of the Graphics class
• setColor(Color r)
• setFont(Font f)
• drawString(String s, int x, int y)
• drawLine(int x1, int y1, int x2, int y2)
• drawRect(int x, int y, int width, int height)
• fillRect(int x, int y, int width, int height)
• drawPolygon(Polygon p)
• etc.

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Misc Custom Painting (example)

• import javax.swing.
• import java.awt.
• public class Welcome extends JApplet
• public void paintComponent(Graphics g)
• Polygon p1 new Polygon()
• p1.addPoint(100, 200)
• p1.addPoint(200, 300)
• p1.addPoint(13, 243)
• g.drawPolygon(p1) // draws outline
• g.fillPolygon(p1) // fills in
• g.drawString(Welcome to Java Programmin)
• showStatus(My first Java Program)

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Summary

• Swing and AWT are designed as a large
  hierarchical library of components that can be
  put together to build a GUI
• Components are created and added to a container.
  Their location and size within a container are
  managed by the containers layout manager
• Applets define an interface for viewing Java
  programs in a web browser

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Next Class

• More GUI Programming
• Event handling
• MP4 due soon, MP5 is out soon