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Revision as of 06:36, 9 August 2013 by hamishwillee (Talk | contribs)

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Navigating between Screens using Java ME

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This code snippet demonstrates how to navigate between three different Screen instances. Screen is the superclass of all high-level user interface classes, such as Form and List.

In practice, the navigation is done by setting the current Displayable to the specific Screen:

private void switchCurrentScreen(Displayable displayable) {

Source file

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.midlet.MIDlet;
public class NavigationMIDlet extends MIDlet implements CommandListener {
private Form firstScreen;
private Form secondScreen;
private Form thirdScreen;
// Navigation commands
private static final Command NEXT_COMMAND =
new Command("Next", Command.OK, 1);
private static final Command PREV_COMMAND =
new Command("Previous", Command.BACK, 1);
private static final Command EXIT_COMMAND =
new Command("Exit", Command.EXIT, 1);;
* Constructor. Constructs the object and initializes displayables.

public NavigationMIDlet() {
// Initialize the screens
private void initFirstScreen() {
firstScreen = new Form("First example screen");
StringItem item = new StringItem("Description",
"This is the first example screen.");
private void initSecondScreen() {
secondScreen = new Form("Second example screen");
StringItem item = new StringItem("Description",
"This is the second example screen.");
private void initThirdScreen() {
thirdScreen = new Form("Third example screen");
StringItem item = new StringItem("Description",
"This is the third example screen.");
private void switchCurrentScreen(Displayable displayable) {
* From MIDlet.
* Called when the MIDlet is started.

public void startApp() {
// The initial display is the first form
* From MIDlet.
* Called to signal the MIDlet to enter the Paused state.

public void pauseApp() {
// No implementation required
* From MIDlet.
* Called to signal the MIDlet to terminate.
* @param unconditional whether the MIDlet has to be unconditionally
* terminated

public void destroyApp(boolean unconditional) {
// No implementation required
* From CommandListener.
* Called by the system to indicate that a command has been invoked on a
* particular displayable.
* @param command the command that was invoked
* @param displayable the displayable where the command was invoked

public void commandAction(Command command, Displayable displayable) {
if (command == EXIT_COMMAND) {
// Exit the MIDlet
} else if (command == NEXT_COMMAND) {
if (displayable == firstScreen) {
} else if (displayable == secondScreen) {
} else if (command == PREV_COMMAND) {
if (displayable == secondScreen) {
} else if (displayable == thirdScreen) {

It is also possible to display an Alert before switching the screen. In addition, the switching can be done only after the user has dismissed the alert. AlertType class defines the type of the alert and whether user interaction is required before the screen is switched (AlertType.CONFIRMATION). To implement showing an informative alert (AlertType.INFO; doesn't require user interaction) before switching the screen, add the following code to the example above:

import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.AlertType;
private void switchCurrentScreen(Alert alert, Displayable displayable) {
Display.getDisplay(this).setCurrent(alert, displayable);
Alert alert = new Alert("Screen changing",
"Switching current screen in a moment...", null, AlertType.INFO);
switchCurrentScreen(alert, firstScreen);


The MIDlet demonstrates navigation between three different screens.

This page was last modified on 9 August 2013, at 06:36.
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