Programming Tutorials

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Using List to create a Menu and Menu items in J2ME

By: Eric Giguere in J2ME Tutorials on 2008年07月10日 [フレーム]

This example creates a list of items (Item1 to Item4) and calls the prepare method whenever an item is selected. The testItem# methods, where # s a number between 1 and 4, call the prepare method and set the name of the menu.

 
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
public class EventEx1 extends MIDlet implements CommandListener {
 // display manager
 Display display = null;
 
 // a menu with items
 List menu = null; // main menu
 // textbox
 TextBox input = null;
 // command
 static final Command backCommand = new Command("Back", Command.BACK, 0);
 static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);
 static final Command exitCommand = new Command("Exit", Command.STOP, 2);
 String currentMenu = null;
 // constructor.
 public EventEx1() {
 }
 /**
 * Start the MIDlet by creating a list of items and associating the
 * exit command with it.
 */
 public void startApp() throws MIDletStateChangeException {
 display = Display.getDisplay(this);
 menu = new List("Menu Items", Choice.IMPLICIT);
 menu.append("Item1", null);
 menu.append("Item2", null);
 menu.append("Item3", null);
 menu.append("Item4", null);
 menu.addCommand(exitCommand);
 menu.setCommandListener(this);
 mainMenu();
 }
 public void pauseApp() {
 display = null;
 menu = null;
 input = null;
 }
 public void destroyApp(boolean unconditional) {
 notifyDestroyed();
 }
 // main menu
 void mainMenu() {
 display.setCurrent(menu);
 currentMenu = "Main"; 
 }
 /**
 * a generic method that will be called when selected any of
 * the items on the list.
 */
 public void prepare() {
 input = new TextBox("Enter some text: ", "", 5, TextField.ANY);
 input.addCommand(backCommand);
 input.setCommandListener(this);
 input.setString("");
 display.setCurrent(input);
 }
 /**
 * Test item1.
 */
 public void testItem1() {
 prepare();
 currentMenu = "item1";
 }
 
 /**
 * Test item2.
 */
 public void testItem2() {
 prepare();
 currentMenu = "item2"; 
 }
 /**
 * Test item3.
 */
 public void testItem3() {
 prepare();
 currentMenu = "item3"; 
 }
 /**
 * Test item4.
 */
 public void testItem4() {
 prepare();
 currentMenu = "item4"; 
 }
 /**
 * Handle events.
 */ 
 public void commandAction(Command c, Displayable d) {
 String label = c.getLabel();
 if (label.equals("Exit")) {
 destroyApp(true);
 } else if (label.equals("Back")) {
 if(currentMenu.equals("item1") || currentMenu.equals("item2") ||
 currentMenu.equals("item3") || currentMenu.equals("item4")) {
 // go back to menu
 mainMenu();
 } 
 } else {
 List down = (List)display.getCurrent();
 switch(down.getSelectedIndex()) {
 case 0: testItem1();break;
 case 1: testItem2();break;
 case 2: testItem3();break;
 case 3: testItem4();break;
 }
 
 }
 }
}

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