Part 1 to building our own Java Swing Components

1
Drawing with Swing

• Part 1 to building our own Java Swing Components

2
Agenda

• Questions
• Build a SWING component today!
• Drawing basics
• Damage management

3
What are common components

• Very similar to those you have in Java AWT
• Window ? JWindow
• Frame ? JFrame
• Component ? JComponent
• Panel ? JPanel
• Button ? JButton
• Label ? JLabel

4
But different right?

• Heavy weight vs. light weight is a well-known
  difference between AWT Swing
• A lot more components available in Swing
• Very subtle differences in how you would build
  your own components
• (good if familiar with AWT)
• http//java.sun.com/products/jfc/tsc/articles/pain
  ting/index.html

5
Swing

• Lots of very nice features in toolkit
  architecture that we like for this class, such
  as
• MVC
• z-ordering

6
Building a Soft Jog Dial
7
How to build your own Swing Component

• Define a class that extends JComponent
• Define the size
• Define its look (paint method)
• http//java.sun.com/docs/books/tutorial/uiswing/pa
  inting/index.html

8
Define class

• import java.awt.
• import javax.swing.
• class JogDial
• extends JComponent
• // variables methods

9
Define dimensions

• Parent will often determine how much space each
  sub component gets
• But components should tell its parent how much
  space it needs in a layout.

10
Define dimensions

• public Dimension getPreferredSize()
• return(getMinimumSize())
• public Dimension getMinimumSize()
• return(new Dimension(400,150))

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Local coordinate system

• Each component has its own coordinate system
  (0,0) - (width-1, height-1)

12
Define look

• Methods involved
• public void paintBorder(Graphics g)
• public void paintChildren(Graphics g)
• public void paintComponent(Graphics g)

13
What happened to the paint method?

• Its still there
• Will call the other three paint methods
• Not recommended that you override it

14
The paintBorder method

• Paints the components border
• Not recommended that you override it
• If this is usedit consumes some of the size of
  the component

15
The paintChildren method

• Paints the components children
• Not recommended that you override it

16
The paintComponent method

• Paints the component
• This is the method you should override

17
Painting shapes

• Methods supported by Graphics object for painting
  shapes
• Lines (drawLine)
• Rectangles (drawRect and fillRect)
• Raised or lowered rectangles (draw3DRect and
  fill3DRect)
• Round-edged rectangles (drawRoundRect and
  fillRoundRect)
• Ovals (drawOval and fillOval)
• Arcs (drawArc and fillArc)
• Polygons (drawPolygon, drawPolyline, and
  fillPolygon)
• http//java.sun.com/docs/books/tutorial/uiswing/pa
  inting/drawingShapes.html

18
Painting text

• Methods supported by Graphics object for painting
  text
• String (drawString)
• http//java.sun.com/docs/books/tutorial/uiswing/pa
  inting/drawingText.html

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Painting text

• Methods supported by Graphics object for painting
  text
• String (drawString)
• http//java.sun.com/docs/books/tutorial/uiswing/pa
  inting/drawingText.html

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Java 2D

• Additional methods for drawing.
• Draw lines of varying thickness
• Fill shapes with gradients textures
• Move, rotate, scale, shear text graphics
• Composite overlapping text graphics
• Anti-aliasing
• http//java.sun.com/docs/books/tutorial/2d/index.h
  tml

21
Java 2D

• import java.awt.geom.
• public void paintComponent(Graphics g)
• Graphics2D g2 (Graphics2D) g
• //// paints component

22
Fonts FontMetrics

• Font font new Font(Helvetica,Font.BOLD,14)
• FontMetrics metrics g2.getFontMetrics(font)
• Or
• FontMetrics metrics component.getFontMetrics(fon
  t)

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FontMetrics methods

• int getAscent(), int getMaxAscent()
• int getDescent(), int getMaxDescent()
• int getHeight()
• int getLeading()
• int getMaxAdvance()
• int bytesWidth(byte, int, int)
• int charWidth(int), int charWidth(char)
• int charsWidth(char, int, int)
• int stringWidth(String)
• int getWidths()

24
Lets draw the JogDial

• Line
• Bead
• Marks text decorating line of speed in
  different directions
• (supports configurable max speed up down)

25
Damage management

• Now that the JogDial is drawnlets make it more
  lively
• Adding a thread that moves the bead a pixel at a
  time to the right until it hits the far right and
  then snaps back to the center

26
Damage management

• Just painting is a problem
• Parts of the drawn output is damagedmust be
  redrawn

27
Damage management

• What happens when we try to repaint the entire
  component each time? Why not do this?
• Itd be nice if we could do something else other
  than just painting

28
Damage management

• Repaint only the damaged area

29
Next time

• Handling input