1. Lab 4 (Lab 2 on Java ME)
Java ME GUI Programming
Pervasive Computing Lab
Prepared by: Tuan Nguyen

2. MIDP User interface
 High level
Screen
Alert Form List TextBox
 Low level
Canvas Graphics

3. Form
Picture from: http://www.javaworld.com/javaworld/jw-05-2005/images/jw-0516-midp1.jpg

4. Let’s Example
 Mobile Restaurant App
 Allow a user to order a
meal remotely using a
mobile phone.
This is a list (List class)

5. List – a class of Screen
String[] mainCourseOffers={"Steak","Lamb","Chicken"};
...
//create the list
lstMainCourse = new List("Select main course:",
Choice.MULTIPLE, mainCourseOffers);
//display the list on the screen
Display.getDisplay(this).setCurrent(lstMainCourse);

6. Add a Command button to the list
//Create a command
cmdNext = new Command("Next", Command.OK, 1);
//Add a command “Next” to the Main Course list
lstMainCourse.addCommand(cmdNext);
//let lstMainCourse listen to the user’s commands
lstMainCourse.setCommandListener(this);

7. Result
 The “Next” command does
nothing now.
 Let’s add another list
called “Dessert List”.
 When the user selects the
Next command, the
Dessert List will be
displayed on the screen.
The “Next” command button

8. Create the Dessert list
String[] dessertOffers = {"Ice Cream", "Chocolate Cake",
"Orange Juice"};
...
//create the Dessert list
lstDessert=new List("Select dessert:",Choice.MULTIPLE,
dessertOffers);
//but not display the dessert list until the user selects
the “Next” command.

9. Implement CommandListener class
public class Restaurant extends MIDlet
implements CommandListener
...
//process commands
public void commandAction(Command command,
Displayable displayable){
String label = command.getLabel();
if(label.equals("Next")){
Display.getDisplay(this).setCurrent(lstDessert);
}
}
...

10. Add an Order Summary screen
 Allow the user see what s/he’s
ordering. How?
1. Create the empty Order
Summary screen (e.g., a form).
2. Add a command “Proceed” to
the Dessert list that navigates to
the Order Summary screen.
3. Add code in the commandAction
method to process the “Proceed”
command.

11. Get the state of all elements of a list
//retrieve selected main courses
boolean[] selectedMainCourses = new boolean[lstMainCourse.size()];
lstMainCourse.getSelectedFlags(selectedMainCourses);
String strMainCourse = "";
for(int i=0; i<lstMainCourse.size(); i++){
if(selectedMainCourses[i]) strMainCourse += mainCourseOffers[i] + ", ";
}
//retrieve selected dessert
boolean[] selectedDessert = new boolean[lstDessert.size()];
lstDessert.getSelectedFlags(selectedDessert);
String strDessert = "";
for(int i=0; i<lstDessert.size(); i++){
if(selectedDessert[i]) strDessert += dessertOffers[i] + ", ";
}
//update the Order Summary form according to the selected main courses...
sItemMainCourse.setText(strMainCourse);
sItemDessert.setText(strDessert);
Display.getDisplay(this).setCurrent(frmOrderSummary);

12. Exercise:
Improve Mobile Restaurant App
Find the completed code for this app on the subject web site.

13. HotelBooking Application
 Purpose: a customer wants to book a room at
Saville Hotel
 The UI can be like this
Items are
Form, Gauge, Spacer, Ima
geItem, TextField
, DateField, StringItem, Ch
oiceGroup

14. Graphics

15. javax.microedition.lcdui.Canvas
class MyCanvas extends Canvas {
public void paint(Graphics g) {
// create a 20x20 black square in the centre
g.setColor(0xFF0000); // make sure it is red
g.fillRect(getWidth()/2–10, getHeight()/2–10, 20, 20);
g.setColor(0x0000FF); // make sure it is blue
g.drawString("Hello World", getWidth()/2, getHeight()/2
- 10, Graphics.HCENTER | Graphics.BASELINE);
}
}

16. References
 Vikram Goyal , J2ME Tutorial,
http://today.java.net/pub/a/today/2005/02/09/j2me1.html, 02/09/2005
 Michael Juntao Yuan & Kevin Sharp, JavaWorld.com,
www.javaworld.com/javaworld/jw-05-2005/jw-0516-midp.html,
05/16/2005
 http://developer.symbian.com/main/oslibrary/java_papers/midp.jsp
 http://developers.sun.com/mobility/apis/articles/wsa/
 Eric Giguere, Databases and MIDP, Part 1: Understanding the Record
Management System,
http://developers.sun.com/mobility/midp/articles/databaserms, 2004
 http://www.java2s.com/Code/Java/J2ME/Persistencestoringandshowin
ggamescores.htm
 http://today.java.net/pub/a/today/2005/05/03/midletUI.html?page=4

17. Time for practice