Simple User Interface Application Using a Label Text Field and Button

The goal of this application is to have the user enter his or her name into a text box, press a button, and have the BlackBerry greet them by name (Figure 4-7). You can compare this application and the process to the iPhone version from Chapter 2.

Figure 4-7. Hello BlackBerry Application Running in the Simulator

First, set up a new BlackBerry Project. We explained how to setup and configure a new BlackBerry project in the previous example. Next, we will create a new project called User Interface and a new class that extends UiApplication called UserInterface.

Replace the contents of the generated UserInterface with the source code of the completed User Interface application that follows.

import net.rim.device.api.ui.*;

import net.rim.device.api.ui.component.*;

import net.rim.device.api.ui.container.*;

public class UserInterface extends UiApplication {

public static void main(String []args) {

UserInterface theApp = new UserInterface(); theApp.enterEventDispatcher();

public UserInterface () {

pushScreen (new UserInterfaceScreen());

class UserInterfaceScreen extends MainScreen implements FieldChangeListener {

LabelField greetingLabel; BasicEditField userNameField; ButtonField helloBtn;

public UserInterfaceScreen() {

LabelField title = new LabelField("XPlatform Dev"); setTitle(title);

greetingLabel = new LabelField(""); add(greetingLabel);

userNameField = new BasicEditField("Name: ", ""); add(userNameField);

helloBtn = new ButtonField("Hello BlackBerry!",^ ButtonField.CONSUME_CLICK);

helloBtn.setChangeListener(this);

add(helloBtn);

public void fieldChanged(Field field, int context) {

greetingLabel.setText("Hello " + userNameField.getText());

public boolean onClose() {

System.exit(0); return true;

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