PROG 38448

Mobile Java Application Development

BlackBerry App Lifecycle Java ME API

BlackBerry App Life Cycle

1.

Application Starts Three ways to start an app: User clicks app icon App starts automatically on startup or reboot App is started by another app Starting point in your application class is main() method 4/26/2020 Wendi Jollymore, ACES 2

BlackBerry App Life Cycle

2.

Application Object Is Created Triggered in the main() method You instantiate your application class that extends UiApplication Application classes with a Ui must extend UiApplication class Can only have one UiApplication instance for any application Otherwise RuntimeException is thrown.

4/26/2020 Wendi Jollymore, ACES 3

BlackBerry App Life Cycle

3.

Event thread is started main() is the main thread or process that’s running Do anything you need to do here before you pass control to BB O/S enterEventDispatcher() method call Takes control of the main thread Draws the main screen and listens for events Won’t return, so if you need something else done in main(), do it first 4/26/2020 Wendi Jollymore, ACES 4

BlackBerry App Life Cycle

4.

5.

Events are processed User events triggered by input from trackball, touch screen, keyboard, etc Other events Application Exits When the last screen is removed from the stack.

Avoid System.exit() !!

Close all screens until the last screen is closed.

Proper clean up of all application state 4/26/2020 Wendi Jollymore, ACES 5

What is the API?

Application Program Interface The collection and definition of building blocks available in a language Descriptions of classes and their public methods http://en.wikipedia.org/wiki/Api Where to read the API docs?

http://www.blackberry.com/developers/docs/ 6.0.0api/index.html

Go to any JDE folder and select BlackBerry JDE API Reference 4/26/2020 Wendi Jollymore, ACES 6

Java ME API

Java ME – Micro Edition For developing mobile apps Runs on custom JVM for BlackBerry BlackBerry Java Virtual Machine MIDP 2.0 Standard– Mobile Information Device Profile http://www.webopedia.com/TERM/M/ MIDP.html

Part of Java ME API used for various mobile devices (not just for RIM) Contains APIs for persistent storage, user interface, networking 4/26/2020 Wendi Jollymore, ACES 7

Java ME API

CLDC – Connected Limited Device Configuration http://www.webopedia.com/TERM/C/C LDC.html

A specification for a stripped down virtual machine For devices with very limited memory Contains minimalist versions of java.lang, java.util, java.io

Contains java.microedition.io for network connections 4/26/2020 Wendi Jollymore, ACES 8

Java ME API

Other API Extensions specific to BlackBerry devices User Interface Persistent Data Storage Networking Event Listeners Application Integration Additional utilities for encryption, compression, location-based services, etc.

4/26/2020 Wendi Jollymore, ACES 9

Using API to Create App

Simplest: Start with two classes An application class The main application where it all starts Extends UiApplication class Three main tasks to perform: Create an instance of the app Create main screen and push onto display stack Start the event dispatch thread 4/26/2020 Wendi Jollymore, ACES 10

Using API to Create App

Simplest: Start with two classes (continued) A screen class A visible display Extends MainScreen class Could have components, images, user input, etc Components = Fields net.rim.device.api.ui.Field

Layout = Managers net.rim.device.api.ui.Manager

4/26/2020 Wendi Jollymore, ACES 11

UiApplication Class

net.rim.device.api.ui.UiApplication

Child of Application class A non-gui program would extend this Base class for all UI applications Contains a screen stack Only top screen is ever visible pushScreen(screen) adds a screen to the stack Lays out and prints the screen object A screen can only be pushed onto the stack once, or exception occurs 4/26/2020 Wendi Jollymore, ACES 12

UiApplication Class

public class MyApp extends UiApplication { public MyApp() { MyScreen scr = new MyScreen(); pushScreen(scr); } // ...

}

4/26/2020 Wendi Jollymore, ACES 13

UiApplication Class

Event dispatcher thread enterEventDispatcher() called on your application class Takes control of main thread Handles all drawing and event handling Never returns; ends when application ends Call this in the application’s main() method 4/26/2020 Wendi Jollymore, ACES 14

UiApplication Class

public class MyApp extends UiApplication { public MyApp() { MyScreen scr = new MyScreen(); pushScreen(scr); } public static void main(String[] args) { MyApp app = new MyApp(); app.enterEventDispatcher(); } }

4/26/2020 Wendi Jollymore, ACES 15

MainScreen Class

net.rim.device.api.ui.container. MainScreen Child of Screen/FullScreen class Has a VerticalFieldManager, title area, default menu, etc In the MainScreen constructor is where you’d create and lay out your main UI 4/26/2020 Wendi Jollymore, ACES 16

MainScreen Class

public class MyScreen extends MainScreen { public MyScreen() { LabelField label = new LabelField(“Hello!"); add(label); LabelField title = new LabelField("Java ME"); this.setTitle(title); } }

4/26/2020 Wendi Jollymore, ACES 17

Hierarchy

It’s interesting to note the inheritance hierarchy of these classes: Object Field ScrollView 4/26/2020 Wendi Jollymore, ACES Manager Screen 18

Exercises and Homework

Exercise: Do the exercise in the Lesson 2 notes For next class: Read Chapter 4 of Beginning BlackBerry 4/26/2020 Wendi Jollymore, ACES 19