Deliver Information, not Just Data

1
Deliver Information, not Just Data

• Design displays carefully
• Visual order and user focus (control contrast)
• Match the medium (mixed metaphors)
• Attention to detail (dont assume anyone can do
  the jobteam approach)
• Screen belongs to User (avoid trying to help the
  user manage the screen)
• Preserve display inertia (localize the response
  to user actionwait for Return to reposition
  list)
• Dont respond too quickly
• Warn the user of proposed changemake change
  predictable and appropriate (measured) response

2
Custom Painting

• As we should by now realize the Swing library is
  divided between containers and components. We
  have used JPanel components for grouping. Now
  will will use them for drawing.
• The coordinate systems for ANY component makes
  the upper lefthand corner (0,0), so the lower
  right hand corner is (width-1, height-1) where
  units are pixels.
• Any border width comes out of the dimensions of
  the component (more accurately, the visible area
  of the component is decreased (inset) by the
  pixels assigned to its border).
• getInsets() obtains a components border width,
  getWidth() and getHeight() obtains the
  components outer dimensions.

3
Repaint()

• When invoked, the componet schedules itself to be
  refreshed in graphics memory. With no arguments,
  the whole component is repainted, but with four
  arguments, only that rectangular portion is
  refreshed. (g.getClipBounds() tells you what
  region of your component is visible on the
  screen)
• Example Code
• CoordinateDemo (p. 861)
• SelectionDemo (p.879)

4
The Graphics Object

• When component.repaint() is invoked the
  paintComponent(Graphics g) method for that
  component is called and it employs a default
  color, font, etc. to do the custom painting.
  After painting the background of the component
  (because of a call to super.paintComponent) the
  method does the drawing requested, then invokes
  paintBorder and finally paintChildren so that any
  components internal to the component will also
  repaint themselves.
• Graphics