Java Swing in 2 hours

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Java Swing (in 2 hours)

• Part 1

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Some numbers

• 14 packages related to UI
• 451 classes at java 1.4 (and counting!)
• 2 hours
• 15 sec / class

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What well cover this session

• What is a GUI
• What is Swing ( some history)
• Some basic Swing concepts
• How to create GUIs (that dont do anything)
• Code samples
• Note about code samples I might use many classes
  in the same file. This is usually NOT the good
  way to do it.

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What is a GUI?
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What is Swing

• Timeline
• 1930- Artie Shaw, Benny Goodman, Glen Miller
  and many others In the mood, etc.
• Java 1.0 AWT (1996)
• Java 1.2 Swing (1998)
• Swing keeps growing, AWT is mostly deprecated.

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Swing vs. AWT

• AWT abstract windows toolkit (cross platform)
• AWT earliest version of Java GUI
• AWT components are heavyweight
• Most Swing components are 'lightweight'
• Do not mix AWT and Swing
• Use Swing

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Some Basic Swing Concepts(a REALLY shallow
overview)

• Every program has at least one Top-Level
  container (JFrame, JWindow, JApplet)
• The Top-Level container contains JComponents
  (JLabel, JButton..). Some components are used as
  Containers for other components (JPanel).
• (J)Component has methods, and can handle events.

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GUI Elements

• Component ? items displayed (widgets)
• Container ? region containing widgets
• Layout ? arrangement of container
• Event ? interactions for GUI

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Smallest Swing Program

• SimplestSwing.java
• SaferSimplestSwing.java
• BetterSimplestSwing.java

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Whats in a JFrame?

• Title
• MenuBar
• ContentPane
• Most of the action is at the ContentPane
• use getContentPane() and add elements to it.

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JPanel

• Is a container for other elements.
• Usually (for now)
• Create a JFrame
• Create a JPanel. Add widgets to the JPanel.
• Add the JPanel to the JFrame content pane.
• ButtonExample.java

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a Customized Component

• ButtonExample2.java

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Some more Widgets

• JPanel
• JButton, JLabel
• TextField
• TextArea
• getText(), setText()
• SomeWidgets.java

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Some more Widgets

• TextArea grows
• Use JScrollPane
• panel.add(new JScrollPane(textarea))
• You can wrap almost any component in a
  JScrollPane..

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Layout Managers

• Who decides on the components placement and size?
  
• A Layout Manager
• JPanels default FlowLayout
• Other layouts
• BorderLayout (ContentPanes default)
• GridLayout
• BoxLayout, GridBagLayout, SpringLayout

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Setting a Layout

• JPanel panel new JPanel(new BorderLayout())
• or
• JPanel panel new JPanel()
• panel.setLayout(new GridLayout(4,3,5,5))

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Flow Layout

• Components are added one after the other, and
  flow to the next line if needed.
• It wont resize the container

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BorderLayout

• Container is splitted into 5 sections NORTH,
  SOUTH, EAST, WEST, CENTER
• The central component is stretched.

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BorderLayout, cont.

• There can be only one component in each section.
• This is usually used to add a toolbar at the
  size of the screen, and a main working area at
  the center.

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BorderLayoutExample

• BorderLayoutExample.java

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GridLayout

• GridLayout is a simple table with a fixed number
  of cells, with all columns and rows equally
  sized.

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Combinations

• You can ofcourse combine layouts --
• JPanel with BorderLayout that contain
  twoJPanels, one of them with GridLayout and the
  other with FlowLayout, etc.

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Play with it

• Simple exercise for home create a calculator
  screen

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Some more widgets

• JCheckBox , JRadioButton
• like JButton, inherit from JAbstractButton
• Learn to use them.

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Others you might want to look at

• JSplitPane
• JTabbedPane
• JMenuBar
• JMenu
• JMenuItem

• JToolTip
• JComboBox
• JList
• JSlider
• JSpinner

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ImageIcons

• The easiest way to add graphics and images.
• ImageIcons can appear on a JLabel or a JButton,
  with or without additional text.
• ImageIconsExample.java
• BetterImageIconsExample.java

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Drawing your own graphics

• Every component has a paint() method thats
  responsible for drawing it.
• In principle, you can just override it and do
  your own painting.
• BUT there are many pitfalls its hard to get it
  right. We wont even try..

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Icons to the rescue

• ImageIcon implements the Icon interface.
• JButton, JLabel can take any Icon.
• We can create our own custom Icons, and draw on
  them.

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The Icon Interface
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• This is called whenever the container of the icon
  paints itself.
• c the containing component.
• x, y the location on the containing component.
• g a Graphics object, that we can draw on.

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Graphics

• Graphics abstract class, supporting (among
  others)
• drawLine(int x1, int y1, int x2, int y2)
• drawOval(int x, int y, int width, int height)
• fillOval(int x, int y, int width, int height)
• drawArc(int x, int y, int width, int height,
  int startAngle,
• int arcAngle)
• setColor(Color c)
• setFont(Font f)
• drawString(String s, int x, int y)

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Custom Icon example

• CustomIconExample.java

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Remember this about Containers

• The structure of containers is your design
  decision and should always be thought through in
  advance
• particularly for managing components
• nesting containers
• Failure to do so usually either results in a
  messy interface, messy code or both.

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Remember this about Components

• There are many components that make your job much
  easier.
• Often, you will be able to customise an existing
  Swing component to do a job for you, instead of
  having to start from scratch

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How to Learn Swing

• Dont even try.
• (to know all of it)
• Learn general framework principles and design
  styles.
• Then use the API reference, and Swing Tutorials
  to discover detailed usage of each component.

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Where to get more info

• Books (but you can do without it)
• Internet Ill put some good links on the course
  web site (under links).
• TRY TO DO STUFF!