Blackberry JAVA DEVELOPMENT ENVIRONMENT Руководство по началу работы - Страница 13

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For a BlackBerry device applicaion to provide a UI, the BlackBerry device application must extend the

net.rim.device.api.ui.UiApplication

to register event listeners, manage threads, and manage UI components.

A UI maintains a stack of

screens already on the stack. When a BlackBerry device application pops a screen off the stack, it redraws the

underlying screens as necessary. Only the screen on the top of the stack receives input events.

See

UiApplication

in the API Reference for more information.

Create a main method for the BlackBerry device application. When you start a BlackBerry device application,

program exectution starts at the

public static void main(String[] args){

}

main()

2. Within the

method, add the following code:

HelloWorld theApp = new HelloWorld();

theApp.enterEventDispatcher();

When you invoke the

application, the BlackBerry device application enters the event thread which runs all drawing and event-

handling code and waits for events on the BlackBerry device application queue.

Create a screen for the HelloWorld application

super()

Invoking

invokes the constructor of the

class provides a UI screen that contains a title section, a separator element, and a single vertical field manager for

maintaining a list of fields. See

LabelField

lets a BlackBerry® device application display a label on a UI. See

for more information.

RichTextField

is a read-only text field you can use to show text in a variety of fonts and formats on a screen.

See

RichTextField

in the API Reference for more information.

Invoking

add(RichTextField("Hello World!"))

HelloWorldScreen

screen. See

Create a class that extends the

final class HelloWorldScreen extends MainScreen {

2. Create a constructor for the

public HelloWorldScreen(){

}

class. This class provides methods for BlackBerry device applications

Screen

objects. As it pushes screens onto the stack, it draws them on top of any other

main()

method.

enterEventDispatcher()

HelloWorldScreen

MainScreen

in the API Reference for more information.

Manager

in the API Reference for more information.

MainScreen

class.

HelloWorldScreen

2: Create a basic BlackBerry device application

method using an instance of the BlackBerry device

superclass,

adds the

RichTextField

class.

MainScreen

. The

LabelField

in the API Reference

to the

Manager

object of the