Mobile UI Development with Java

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Mobile UI Development with Java

• Nima Sarshar

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Java Micro Edition

• Java ME deals with constraints of small devices.
• Allows to create Java applications running on
  small devices with limited memory, display and
  power capacity.

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Elements of Java ME

• a configuration provides the most basic set of
  libraries and virtual machine capabilities for a
  broad range of devices,
• a profile is a set of APIs that support a
  narrower range of devices, and
• an optional package is a set of
  technology-specific APIs.

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Basic Configurations

• one to fit small mobile devices called Connected
  Limited Device Configuration (CLDC)
• one to target more capable mobile devices like
  smart-phones and set top boxes called Connected
  Device Profile (CDC).

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Source http//java.sun.com/javame/technology/ind
ex.jsp
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CLDC
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Mobile Information Device Profile

• A widely adopted example is to combine the CLDC
  with the Mobile Information Device Profile (MIDP)
  to provide a complete Java application
  environment for mobile phones and other devices
  with similar capabilities.

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CDC
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Connected Device Profile-CDC

• Targets larger devices with more capacity and
  with a network-connection, like high-end personal
  digital assistants, and set-top boxes
• Closer to the Java Platform Standard Edition (SE)

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Java ME Platform for Converged Services- covers
everything!
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MIDP Mobile Information Devices Profile
http//developers.sun.com/mobility/midp/articles/g
uiapis/
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MIDP UI API (!)

• They are all in javax.microedition.lcdui
• High level UI
• Screen class and its subclasses
• Item and its subclasses
• High-level API lets the device choose itw own
  native look-and-feel on the handset

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Same Code of Two Devices
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MIDP High Level UI

• Alert (used for showing dialog boxes and
  warnings)
• ChoiceGroup (used for showing group of checkboxes
  or radio buttons)
• DateField (used for selecting dates and times)
• Form (used for displaying the subclasses of Item)
• Gauge (used to showing the progress of an
  operation or process, but it can also be used to
  represent the percent of a whole)
• ImageItem (used for showing images in high-level
  UI applications)
• List (used for showing lists and combo boxes)
• StringItem (used for showing simple text strings)
• TextBox (used for entering text)
• TextField (an alternate method used for entering
  text)

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Low-Level API

• Designer now has more control, but has to take
  care of the details
• Canvas class and derivatives
• Graphic object

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MIDP 2.0

• Bridges between low and high level UI APIs
• AnimatedImage (which allows the creation and
  rendering of animated images)
• FileSelector (a mechanism for browsing
  directories and selecting files on the file
  system)
• TabbedPane (a mechanism for creating and
  displaying a tabbed pane)

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Personal Basis and Personal Profiles

• The Connected Device Configuration (CDC) are for
  devices with power more than a phone but
• has less than a desk top
• High-end mobile phones and PDAs.
• The Personal Basis Profile has a very small
  subset of the Java SE Abstract Windowing Toolkit
  (AWT) libraries.
• No buttons, menus, list, textboxes, scrollbars,
• The Personal Profile almost a completely
  implements AWT, and even provides support for
  applets.

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Example Personal Profile
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Scalable 2D Vector Graphics API - versions 1.0
and 2.0
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3D Graphics APIs - M3G versions 1.0 and 2.0 and
OpenGL ES
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Advanced Graphics and User Interface (AGUI)
Finally supports Swing

• java.awt
• java.awt.font
• java.awt.geom
• java.awt.image
• java.nio
• javax.imageio
• javax.imageio.event
• javax.imageio.metadata
• javax.imageio.stream
• javax.microedition.plaf
• javax.microedition.agui.event
• javax.swing
• javax.swing.border
• javax.swing.event
• javax.swing.plaf
• javax.swing.table
• javax.swing.text
• javax.swing.undo

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Summary
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More on MIDP
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Display

• Display
• The Display class provides access to the physical
  screen.
• Only one instance of the Display object is
  allowed for each MIDlet.
• We can obtain the instance of the Display class
  by passing the MIDlet object to the static
  Display.getDisplay() method.
• public static Display getDisplay (MIDlet m)

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Displayable

• Methods in Display class display Displayable
  objects to the physical screen!
• The Displayable object represents a view of the
  screen
• In MIDP, there is only one Displayable object
  visible at any given time.
• setCurrent() method is used to switch the view.
• public void setCurrent(Displayable d)
• public void setCurrent(Alert a, Displayable d)
• public void setCurrentItem(Item item)
• public Displayable getCurrent()

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Displayable

• The Displayable class is an abstract
  representation of a full screen of display
  content.
• We can query whether a Displayable object is
  shown on the LCD by calling its isShown() method.
  
• The Displayable class allows us to query the size
  of the screen display area.
• public int getWidth()
• public int getHeight()
• public boolean isShown()

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Displayable

• The Displayable class also provides methods to
  add and manipulate the title and ticker of the
  display area.
• public void setTitle(String title)
• public String getTitle()
• public void setTicker (Ticker ticker)
• public Ticker getTicker ()
• A ticker is an optional line of text string
  scrolling across the top of the display area.

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• public interface CommandListener void
  commandAction(Command command, Displayable
  displayable)
• public void addCommand(Command cmd)
• public void removeCommand(Command cmd)
• public void setCommandListener(CommandListener l)

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Low-level API

• The Canvas abstract class defines an abstract
  method paint(Graphics g).
• Each concrete Canvas subclass must implement the
  paint() method to specify how to draw itself on
  the screen.
• When a Canvas object is displayed, the paint()
  method is automatically invoked. The Graphics
  object is passed in by the Java runtime.
  Developers do not invoke the paint() method
  directly.
• When the screen needs updating, the application
  calls repaint(), which schedules the runtime to
  call the paint() method.

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• Graphics
• The Graphics class provides methods to do the
  actual drawing on a Canvas.
• It is usually passed into the Canvas.paint()
  method.
• Lines
• Outline of geometric objects such as arcs and
  rectangles
• Filled geometric objects
• Text strings
• Images
• public void drawChar(char c, int x, int y, int
  anchor)
• public void drawSubstring(String str, int offset,
  int len, int x, int y, int anchor) public void
  drawImage(Image img, int x, int y, int
  anchor)public void drawLine(int x1, int y1, int
  x2, int y2)
• public void drawArc(int x, int y, int width, int
  height, int startAngle, int arcAngle)

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Key-event model

• When the user presses a key, the MIDP runtime
  calls the Canvas.keyPressed() method and passes
  the key code.
• By default, the keyPressed() method does nothing.
  It just ignores the event.
• The Canvas subclass overrides it to respond to
  the event.
• public void keyPressed(int keyCode)
• public void keyReleased(int keyCode)
• public void keyRepeated(int keyCode)

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