交通大學資訊工程系蔡文能第1頁第1頁 programming in java j2me 汪益賢蔡文能...

交通大學資訊工程系蔡文能第 1頁

Programming in Java

J2ME

汪益賢蔡文能交通大學資訊工程學系

http://www.csie.nctu.edu.tw/~tsaiwn/java/

Java J2ME

交通大學資訊工程系 9-第 2頁

Outline

Java ME

Java ME Architecture

Java ME Specification

Learning J2ME CLDC 1.0 / MIDP 2.0 APIs

User Interface (lcdui)

Input/Output (RMS)

Networking

練習： Calculator or Monty Hall (手機版 )

Java J2ME


Java ME (formerly J2ME)

Java Platform, Micro Edition Provides a robust, flexible environment for applications running

on a broad range of other embedded devicesMobile phones

PDAs

TV set-top boxes

Printers

Applications based on Java ME specifications are written once for a wide range of devices, yet exploit each device’s native capabilities. Java Mobile Games

Java J2ME


Java ME Games

The most popular application Java-enabled devices grow rapidly. Java mobile games almost become the name of Java mobile

applications.

Nokia Snake ThinkNewIdea MJ16 JoyPark-Rich

Java J2ME


Java J2ME


3D Mobile Java Game

Java J2ME


Pac-Manhattan

http://www.pacmanhattan.com/

Java J2ME


Java ME Architecture

VMs

Configurations

Profiles

Optional Packages

Java J2ME


Java Platform Editions

Java J2ME


J2ME Architecture

Source: http://www.j2mer.idv.tw

多層次的架構 (一堆很容易搞混的名詞 ) 基本上，把 Profile, Configuration 都當作是 Package 來思考

Java J2ME


VMs for Java ME

KVM (K Virtual Machine) for CLDC 16-bit or 32-bit processor with a clock speed of 16MHz or higher At least 160KB memory (128KB for VM and the CLDC library +

32KB for runtime heap space) Low power consumption (battery) Wireless with limited bandwidth

JVM (Java Virtual Machine) for CDC 32-bit processor More than 512KB memory + 128KB runtime heap space Unlimited power supply Fast network Target devices: smartphones, TV set-top boxes, and so on.

Java J2ME


Configurations

Specifies the Java programming language features supported.

Specifies the Java virtual machine features supported.

Specifies the basic Java libraries and APIs supported.

Two configurations are defined: CLDC (Connected, Limited Device Configuration) CDC (Connected Device Configuration)

Java J2ME


Profiles

Provide specific APIs for a certain device type. CLDC

MID Profile (Mobile Information Device Profile) Screen resolution: 96x54. Memory: 256KB for MIDP components,

128KB runtime space, 8KB persistent space.

PDA Profile Screen resolution: 160x160.

CDCFoundation Profile

No GUI

Personal Basis Profile Lightweight component

Personal Profile Full AWT and Applet (No Swing and Java 2D)

Java J2ME


Optional Packages

A set of technology-specific APIs that extends the functionality of a Java application environment. Ex:

Wireless Messaging API (WMA) For CLDC 1.0 / MIDP 2.0 Provides access to wireless communication resources like Short Message

Service (SMS).

Mobile Media API (MMAPI) For CLDC 1.0 / MIDP 1.0 Provides audio, video and other time-based multimedia support.

JDBC For CDC / FP 1.0

Java J2ME


Focused Specifications in This Course

The CLDC Specification Currently version 1.1 (JSR 139) No Floating point in version 1.0 (CLDC 1.0 不支援實數 )

The MIDP Specification Currently version 2.0 (JSR 118)

Note that JSR (Java Specification Request) is the actual description of proposed and final specifications for a new Java API that is submitted to the JCP (Java Community Process). (註 : JSR 類似 RFC)

Java J2ME


Relationship between CDC/CLDC and J2SE

J2SE CDC CLDC

Java J2ME


The CLDC Specification

Java language and VM features

Security Classfile verification

Reduced APIs Core Java libraries (java.lang.*, java.util.*) IO Networking

Java J2ME


Constraints on Java Language Specification

No floating point (float and double) But CLDC 1.1 support floating point

No finalization (Object.finalize())

Limited error handling

Java J2ME


Constraints on KVM

No JNI

No user-defined class loader

No reflection

No thread groups and daemon threads

No weak references java.lang.ref.WeakReference

Java J2ME


Classfile Verification

Java J2ME


Sun Java Wireless Toolkit for CLDC Buffer Overflow Vulnerabilities

http://www.vupen.com/english/advisories/2008/3439

Two vulnerabilities have been identified in Sun Java Wireless Toolkit (WTK) for CLDC (Connected Limited Device Configuration), which could be exploited by local attackers to gain elevated privileges. These issues are caused by unspecified buffer overflow errors which may allow a malicious program downloaded and executed in the WTK to execute arbitrary code with the privileges of the WTK process.

Affected: Sun Java Wireless Toolkit for CLDC version 2.5.2 and prior.

Solution: Upgrade to Sun Java Wireless Toolkit for CLDC version 2.5.2_01 :http://java.sun.com/products/sjwtoolkit/

Java J2ME


The MIDP Specification

Application Life-cycle Management

User Interface

Event Handling

Record Management System (RMS)

Java J2ME


MID Profile

MIDP 1.0 Packages: javax.microedition.lcdui.* javax.microedition.rms.* javax.microedition.midlet.* javax.microedition.io.*

MIDP 2.0 Added Packages: java.microedition.lcdui.game.* javax.microedition.media.* javax.microedition.media.control.* javax.microedition.pki.*

MIDP 2.0 supports socket connection that is not available in 1.0.

Java J2ME


Constraints on Libraries

Only majority of the class libraries are included. ex:

No java.io.BufferedReader/Writer,java.io.FileReader/Writer/ InputStream/OutputStream

No java.awt.*

…

Java J2ME


Hardware Consideration

The screen size is small.

Different mobile devices have different constraints. Different screen size. Different Input Method

No mouse

ITU keyboard (0~9, *, #, 上下左右 , …)

Touch pad

Different available memory

Java J2ME


Learning Java ME (CLDC 1.0 / MIDP 2.0)

Development Environment Sun Java Wireless Toolkit (currently WTK 2.5.2)

http://java.sun.com/products/sjwtoolkit/

The Wireless Toolkit has been integrated into Java ME SDK 3.0.

Deployment

Your First MIDP Program class HelloMidlet extends MIDlet

Java J2ME


Sun Java Wireless Toolkit

A toolbox for developing wireless applications that are based on CLDC and MIDP. Cell phones Mainstream personal digital assistants Other small mobile devices

The toolkit includes the Emulation environments Performance optimization and tuning features Documentation Examples

Java J2ME


Deployment

There are two ways to deploy a MIDlet suite. Direct uses some direct connection between the device and the

development platformcommonly cable, infrared, or Bluetooth link

Over-The-Air provisioning (OTA) uses the device’s built-in browser to install a MIDlet suite from a remote server

Java J2ME


JAD and JAR Files

The basic components of any MIDlet suite you will deliver Java Application Descriptor (JAD) file

the location and size of the JAR file

the configuration and profile requirements

attributes

Java Archive (JAR) file

在 product deployment 主題中討論

Java J2ME


Your First MIDP Program: Hello MIDPimport javax.microedition.midlet.*;

import javax.microedition.lcdui.*;

public class HelloMidlet extends MIDlet implements CommandListener

{

private Form mainForm;

public HelloMidlet() //no-argument constructor

{

mainForm = new Form("HelloMIDlet");

mainForm.append(new StringItem(null, "Hello, MIDP!"));

mainForm.addCommand(new Command("Exit", Command.EXIT, 0));

mainForm.setCommandListener(this);

}

protected void startApp()

{

Display.getDisplay(this).setCurrent(mainForm);

}

protected void pauseApp() {}

protected void destroyApp(boolean b) {}

public void commandAction(Command c, Displayable s)

{

notifyDestroyed(); //destroy the MIDlet

}

}

Java J2ME


The Life Cycle of A MIDletWhen a MIDlet begins execution, the application management software (AMS) first calls the zero-argument constructor to create a new instance of the MIDlet. Then, the AMS places the MIDlet in the Paused state.

startApp() shift the MIDlet to the Active state allocate resources, such as record stores, network

connections, and UI components.

pauseApp() The MIDlet is not being terminated, but it should

release some resources.

destroyApp(boolean b) The MIDlet is terminated. Release any resources

acquired.

Java J2ME


Controlling the MIDlet State

notifyPaused() – enter the Paused state.

notifyDestroyed() – inform the AMS that the MIDlet can now be considered Destroyed.

destroyApp(boolean b) If this boolean is true, the MIDlet will be in the Destroyed state when

destroyApp() returns. If this boolean is false, the MIDlet can request not to enter the Destroyed

state by throwing a MIDletStateChangeException.

Java J2ME


Essential APIs

User Interface (lcdui) javax.microedition.lcdui High-Level API: Form, Alert/List/TextBox Low-Level API: Canvas/GameCanvas, Font/Graphics/Image Sound

Input/Output (RMS)

Networking HttpConnection StreamConnection SocketConnection

Java J2ME


Essential APIs1. User Interface

The GUI classes included in the MIDP are not based on AWT/Swing. The AWT is designed for desktop computers and optimized for these devices,

such as window management. The AWT assumes certain user interaction models, such as mouse.

The MIDP UI consists of two APIs. High-Level API

Portability Gives you little control over its look and feel

Implemented by subclasses of the Screen class

Low-Level APIControl of graphic elements and input events

Implemented by the Canvas and Graphics classes

All the UI classes are placed in the javax.microedition.lcdui package.

Java J2ME


javax.microedition.lcdui Package

Java J2ME


The MIDP GUI Programming Model

The Display class is the display manager Instantiated for each active MIDlet Provides information about the device’s display capabilities.

Only one screen can be visible at a time, and the user can traverse only through the items on that screen. A screen is made visible by calling the Display.setCurrent() method.

There are three types of screens: Screens that encapsulate a complex user interface component

Alert, List, or TextBox (High-level API)

Generic screens Form (High-level API)

Screens used within the context of the low-level APICanvas (Low-level API)

Java J2ME


Example of High-Level API

GuiTest.java Screens that encapsulate a complex user interface component

TextBox

List

Alert Generic screens

Form

Java J2ME


GuiTests: Main Menu (List)import javax.microedition.lcdui.*;

import javax.microedition.midlet.*;

public class GuiTests extends MIDlet implements CommandListener {

private List mainMenu;

private static final Command exitCommand = new Command("Exit", Command.STOP, 2); //priority:2

public GuiTests() {

mainMenu = new List("Test Components", Choice.IMPLICIT);

mainMenu.append("Test TextBox", null);

mainMenu.append("Test List", null);

mainMenu.append("Test Alert", null);

mainMenu.append("Test Form", null);

mainMenu.addCommand(exitCommand);

mainMenu.setCommandListener(this); //見下一頁 mainMenu.setTicker(new Ticker(“Test GUI Components”)); //跑馬燈 showMainMenu();

}

public void startApp() {}

public void pauseApp() {}

/*略 */

private void showMainMenu() {

Display.getDisplay(this).setCurrent(mainMenu);

currentMenu = "Main";

}

}

Java J2ME


GuiTests: TextBoxpublic class GuiTests extends MIDlet implements CommandListener {

private TextBox textBoxf = new TextBox("Enter Some Text:", "", 10, TextField.ANY);

private static final Command backCommand = new Command("Back", Command.BACK, 0); //priority:0

private String currentMenu;

public GuiTests() {

textBox.addCommand(backCommand);

textBox.setCommandListener(this);

textBox.setTicker(new Ticker("Testing TextBox")); //跑馬燈 }

private void showTextBox() {

textBox.setString("");

Display.getDisplay(this).setCurrent(textBox);

currentMenu = "input";

}

public void commandAction(Command c, Displayable d) {

List down = (List)Display.getDisplay(this).getCurrent();

switch(down.getSelectedIndex()) {

case 0: showTextBox(); break;

case 1: showList(); break;

case 2: showAlert(); break;

case 3: showForm(); break;

}

}

}

Java J2ME


GuiTests: Listpublic class GuiTests extends MIDlet implements CommandListener {

private List list = new List("Choose Items", Choice.MULTIPLE);


public GuiTests() {

list.addCommand(backCommand);

list.setCommandListener(this);

list.setTicker(new Ticker("Testing List"));

list.append("Item 1", null);



}

private void showList() {

Display.getDisplay(this).setCurrent(list);

currentMenu = "list";

}


List down = (List)Display.getDisplay(this).getCurrent();

switch(down.getSelectedIndex()) {

case 0: showTextBox(); break;

case 1: showList(); break;

case 2: showAlert(); break;

case 3: showForm(); break;

}

}

}

Java J2ME


GuiTests: Alertpublic class GuiTests extends MIDlet implements CommandListener {

private Alert soundAlert = new Alert("sound Alert");

private void showAlert() {

soundAlert.setType(AlertType.ERROR);

soundAlert.setString("** ERROR **");

Display.getDisplay(this).setCurrent(soundAlert); //Play Sound

}

}

Java J2ME


GuiTests: Form (1/2)public class GuiTests extends MIDlet implements CommandListener {

private Form form = new Form("Form for Stuff");

private Gauge gauge = new Gauge("Progress Bar", false, 20, 9);

private DateField date = new DateField("Today's date: ", DateField.DATE);

private TextField textfield = new TextField("TextField Label", "abc", 12, 0);

private ChoiceGroup choice = new ChoiceGroup("choice", Choice.EXCLUSIVE,

new String[]{"choice 1", "choice 2"}, null);


private static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);

private static final Command exitCommand = new Command("Exit", Command.STOP, 2); //priority:2

private String currentMenu;

public GuiTests() {

form.append(new Spacer(2, 2));

form.append(new StringItem("label", "text"));

form.append(choice);

form.append(gauge);

form.append(textfield);

form.append(date);

form.addCommand(backCommand);

form.addCommand(mainMenuCommand);

form.addCommand(exitCommand);

form.setCommandListener(this);

}

//接下頁

Java J2ME


//接上頁 private void showForm() {

Display.getDisplay(this).setCurrent(form);

java.util.Date now = new java.util.Date();

date.setDate(now);

currentMenu = "form";

}


String label = c.getLabel();

if(label.equals("Exit")) {

try { destroyApp(true); }

catch(Exception e) {}

} else if(label.equals("Back")) {

if(currentMenu.equals("form")) {

int index = choice.getSelectedIndex();

mainMenu.setTitle("Form choice: " + index + " text:" + textfield.getString());

}

showMainMenu();

} else if(label.equals("Main")) {

showMainMenu();

} else {/*略 */}

}

}

GuiTests: Form (2/2)

Java J2ME


Low-level APIs

Canvas Not component and container architecture It is really a canvas.

GameCanvas Add double buffering support. MIDP 2.0

Graphics

Font

Image

Java J2ME


Using Graphics

The Graphics object is obtained in the paint() method of the Canvas class.

The Graphics class is similar to that of AWT, but with limited capabilities. Two basic kinds of drawing

Primitive graphics (shapes and text)

PNG Images (opaque, transparent, and translucent)

Provides a drawing contextThe current drawing area

The current drawing color

The Coordinate System

The Two Forms of the Canvas’s repaint() Method public void repaint()

public void repaint(int x, int y, int width, int height)

Canvas

x

y

(0,0)

(width-1, height-1)

Java J2ME


Painting Shapes and Text

The Graphics class can draw the following kinds of shapes: Lines: drawLine() Triangle: fillTriangle() MIDP 2.0 Rectangles: drawRect(), fillRect() Round-edged rectangles:

drawRoundRect(), fillRoundRect() Arcs: drawArc(), fillArc() Text:

drawChar(), drawChars(), drawString(), drawSubstring()

Java J2ME


Using Fonts

static Font getFont(int face, int style, int size); Face: FACE_SYSTEM, FACE_MONOSPACE, or FACE_PROPORTIONAL Style: STYLE_PLAIN or a combination of STYLE_BOLD, STYLE_ITALIC, and

STYLE_UNDERLINED Size: SIZE_SMALL, SIZE_MEDIUM, or SIZE_LARGE

Get font information:

Font font1 = Font.getFont(Font.FACE_PROPORTIONAL, Font.STYLE_ITALIC | Font.STYLE_BOLD, Font.SIZE_LARGE);Font font2 = Font.getFont(Font.FACE_MONOSPACE, Font.STYLE_UNDERLINED, Font.SIZE_SMALL);Font font3 = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);protected void paint(Graphics g){ g.setFont(font1); g.drawString("Proportional", 10, 10, anchor); g.setFont(font2); g.drawString("Monospace", 10, 35, anchor); g.setFont(font3); g.drawString("Default Font", 10, 60, anchor);}

Enjoy J2ME getHeight()

stringWidth()

getBaseLinePosition()

Java J2ME


Anchor

The drawing of text and images is based on “anchor points.” Anchor points are used to minimize the amount of computation required when placing text.

void drawString(String text, int x, int y, int anchor);

boolean drawImage(Image img, int x, int y, int anchor);

Anchor value (bit mask)Horizontal: LEFT, HCENTER, RIGHT

Vertical: TOP, VCENTER, BASELINE, BOTTOM

EX: Graphics.LEFT | Graphics.TOP

LEFT HCENTER RIGHT

TOP

VCENTER

BASELINE

BOTTOM

Java J2ME


Using Images

Loading Images

Displaying Images

Performing Animation

Double Buffering

Java J2ME


Loading ImagesUsing the Image.createImage() static methods It is easy to get an Image object if image data is in PNG format.

Image Types: Immutable images: cannot obtain Graphics object from them

createImage(String pngFileName)createImage(Image source, int x, int y, int w, int h, int transform)createImage(InputStream stream)createImage(Image source)createImage(byte[] data, int imageOffset, int imageLength)createRGBImage(int[] rgb, int w, int h, boolean processAlpha)

Mutable images: can obtain Graphics object from themcreateImage(int w, int h)

Java J2ME


Displaying Images

Draw normal sized images boolean drawImage(Image img, int x, int y, int

anchor)

Draw rotated, mirrored images createImage(srcImage, 0, 0, w, h, transform) MIDP 2.0

Transform constants are defined in Sprite class TRANS_NONE, TRANS_MIRROR TRANS_ROT90, TRANS_ROT180, TRANS_ROT270 TRANS_MIRROR_ROT90, TRANS_MIRROR_ROT180, TRANS_MIRROR_ROT270

Draw clipped images Use translate() and setClip() of Graphics to perform.

Draw scaled images No support!

Java J2ME


Translation and ClippingTranslates the origin of the graphics context to the given point.translate(int x, int y)

Sets the current clip to the specified rectangle. Rendering operations have no effect outside of the clipping area. setClip(int x, int y, int w, int h)

Canvas

x

y

(-a,-b)

(width-a-1, height-b-1)

(0,0)

After call g.translate(a, b)and g.setClip(0, 0, w, h)

Canvas

w

h

Java J2ME


Performing Animation

Creating the Animation Loop Every program needs an animation loop to perform animation by

drawing at regular intervals. This loop should be in its own thread and never be in the paint() method.

duke0.png, duke1.png, … , duke9.png

Java J2ME


Double Buffering

MIDP 1.0 Do it by yourself.

if(offImage == null)

{

offImage = Image.createImage(getWidth(), getHeight());

offG = offImage.getGraphics();

}

//performing painting

g.drawImage(offImage, 0, 0, Graphics.TOP | Graphics.LEFT);

MIDP 2.0 The GameCanvas class do it for you.

flushGraphics();

flushGraphics(int x, int y, int w, int h);

Java J2ME




public class AnimationMidlet extends MIDlet

{

private AnimationCanvas canvas;

public AnimationMidlet()

{

try { canvas = new AnimationCanvas(); } catch(Exception e) {}

}

public void startApp()

{

Display.getDisplay(this).setCurrent(canvas);

}

public void pauseApp()

{

}

public void destroyApp(boolean unconditional)

{

}

}

Animation Canvas (1/3)

Java J2ME



import javax.microedition.lcdui.game.*;

public class AnimationCanvas extends Canvas {

private int dukeIndex = 0;

private Image[] duke = new Image[10];

private Image[] dukeMirrored = new Image[10];

private Image offImage;

private Graphics offG;

public AnimationCanvas() throws Exception {

for(int i = 0; i < duke.length; i++) {

duke[i] = Image.createImage("/res/duke" + i + ".png"); //immutable image

dukeMirrored[i] = Image.createImage(duke[i], 0, 0, duke[i].getWidth(), duke[i].getHeight(), Sprite.TRANS_ROT180); //製造旋轉後的圖

}

new MyThread().start(); // 產生一個 thread 來執行動畫 }

protected void paint(Graphics g) {

if(offImage == null) {

offImage = Image.createImage(this.getWidth(), this.getHeight()); //mutable image


}

//清除背景 offG.setColor(255, 255, 255);

offG.fillRect(0, 0, this.getWidth(), this.getHeight());

//接下頁

Animation Canvas (2/3)

Java J2ME


Animation Canvas (3/3) //接上頁 offG.drawImage(duke[dukeIndex], 0, 0, Graphics.TOP | Graphics.LEFT);

offG.drawImage(dukeMirrored[dukeIndex], 0, 70, Graphics.TOP | Graphics.LEFT);

drawClippedDuke(offG, 60, 0); //繪製切割過的圖 g.drawImage(offImage, 0, 0, Graphics.TOP | Graphics.LEFT);

}

private void drawClippedDuke(Graphics g, int x, int y) {

g.setClip(x, y, duke[dukeIndex].getWidth()/2, duke[dukeIndex].getHeight()); //設定 clipper

g.drawImage(duke[dukeIndex], x, y, Graphics.TOP | Graphics.LEFT);

g.setClip(0, 0, this.getWidth(), this.getHeight()); //恢復 }

class MyThread extends Thread {

public void run() {

while(true) {

dukeIndex = (dukeIndex + 1) % duke.length;

repaint();

//等待 100 milliseconds，等於每秒更新 10次 try { Thread.sleep(100); }

catch(Exception e) {}

}

}

}

}

Java J2ME


Processing Input Events

The Canvas class defines the following ITU Key codes: KEY_NUM{0-9} KEY_STAR (*) KEY_POUND (#) UP, DOWN, LEFT, RIGHT (logic key event) GAME_{A-D} (logic key event)

Override the following method to process key events: For keyboard:

keyPressed(), keyRepeated(), keyReleased()

Use getGameAction() to get logic key event

For touch pad:pointerPressed(), pointerDragged(), pointerReleased()

Java J2ME


Example: Key Events (1/2)public class AnimationCanvas extends Canvas {

private int x = 30, y = 60;

private int code = 0;

private int action = 0;

private long interval = 100L;

private boolean bAnimation = true;

protected void paint(Graphics g)

{

if(offImage == null)

{

offImage = Image.createImage(this.getWidth(), this.getHeight());


}

offG.setColor(255, 255, 255);

offG.fillRect(0, 0, this.getWidth(), this.getHeight());

offG.setColor(0, 0, 0);

offG.drawImage(duke[dukeIndex], x, y, Graphics.TOP | Graphics.LEFT);

offG.drawImage(dukeMirrored[dukeIndex], x, y + 70, Graphics.TOP | Graphics.LEFT);

drawClippedDuke(offG, x + 60, y);

offG.drawString("code = " + code + " action = " + action + " interval = " + interval, 0, 0, Graphics.TOP | Graphics.LEFT);

g.drawImage(offImage, 0, 0, Graphics.TOP | Graphics.LEFT);

}

//接下頁

Java J2ME


Example: Key Events (2/2) class MyThread extends Thread {

public void run() {

while(true) {

if(bAnimation) { dukeIndex = (dukeIndex + 1) % duke.length; repaint(); }

try { Thread.sleep(interval); } catch(Exception e) {}

}

}

}

protected void keyPressed(int keyCode) {

code = keyCode;

action = getGameAction(keyCode);

switch(action) {

case UP: y -= 5; break;

case DOWN: y += 5; break;

case LEFT: x -= 5; break;

case RIGHT: x += 5; break;

}

switch(code) {

case KEY_NUM0: case KEY_NUM1: case KEY_NUM2:



case KEY_NUM9: interval = (keyCode - KEY_NUM0 + 1) * 50; break;

case KEY_STAR: bAnimation = !bAnimation; break;

}

}

}

Java J2ME


Playing Sound

MIDP 1.0 does not specifies any relative APIs! Use vendor specified APIs to play sound. Use alert sound defined in AlertType class.

INFO, WARNING, ERROR, ALARM, CONFIRMATION

Ex: AlertType.INFO.playSound(Display display)

MIDP 2.0 Use javax.microedition.media.Player to play sound.

Wave

MIDI

Java J2ME


Example: Sound Playerimport javax.microedition.midlet.*;


import javax.microedition.media.*;

import java.io.*;

public class SoundMidlet extends MIDlet {

public SoundMidlet() {

try { //MIDP 2.0

Player player;

InputStream is = getClass().getResourceAsStream("/res/start.wav");

player = Manager.createPlayer(is, "audio/X-wav");

player.prefetch(); // 把聲音資料預先讀到 buffer 中，這樣開始播放時不會 delay

//player.setLoopCount(-1); //一直重複播放 player.start();

Thread.sleep(3000);

} catch(Exception e) {}

}

public void startApp() {

Display.getDisplay(this).setCurrent(canvas);

//MIDP 1.0

AlertType.INFO.playSound(Display.getDisplay(this));

}

}

Java J2ME


Guidelines for Programming UI for MID Devices

Make the MIDlets’ user interface simple and easy to use.

Use the high-level API so your MIDlets are portable across handheld devices.

If your application requires you to use the low-level API, keep to the platform-independent part of the low-level API. This means your MIDlets should not assume any other keys than defined in the the Canvas class.

MIDlets should not depend on any specific screen size; they should query the size of the display and adjust accordingly.

Entering data through a handheld device can be tedious. If possible, provide a list of choices that the user can select from.

Java J2ME


Essential APIs 2. Input/Output in MIDP

Review IO classes in Java SE Byte streams are used to read and write binary data such as

images and sounds. Character streams can handle any 16-bit characters in the

Unicode character set.

However, neither CLDC nor MIDP provides APIs for access to file systems on mobile devices or external memory cards. Not all MIDP devices have file systems, and the creators of those that do may not want to expose them to

applications.

Java J2ME


Character Stream Family in MIDP

Java J2ME


Byte Stream Family in MIDP

System.in

System.outSystem.err

Java J2ME


Alternatives to File IO

The alternative to FileInputStream getClass().getResourceAsStream(file) returns an InputStream instance.

Example:

InputStream inputStream = getClass().getResourceAsStream("myPicture.jpg");

How about FileOutputStream? MIDP Record Management System (RMS)

Java J2ME


MIDP RMS

Record Management System (RMS) is a persistent storage for MIDlets. In Java SE, they are JDBC and Object Serialization APIs.

RMS consists of a collection of records. Data written into those records will remain persistent after the

MIDlet exits. When you invoke the MIDlet again, it can retrieve data from the

persistent record store.

RMS APIs provides the following functionality: Manipulate (add and remove) records within a record store. Share records in the same application. MIDP 2.0 allows you to share records in different applications.

Java J2ME


Using RMS (1/2)

Package: javax.microedition.rms

Usages: Open a Record Store

RecordStore db = RecordStore.openRecordStore("name", true); the name is case sensitive, and cannot be more than 32 characters long. true means that create the record store if not exist.

Create a New Record (ID is started from 1)byte[] data = textfield.getString().getBytes();

int id = db.getNextRecordID(); // 取得新增資料時，會被指定的 ID

db.addRecord(data, 0, data.length); //新增資料， ID 是 db 指定的

Java J2ME


Using RMS (2/2)

Read Data from the Record Storebyte[] data = db.getRecord(1); // 取得 ID = 1 的資料if(data != null)

{

textfield.setString(new String(data));

}

Delete a Record from the Record StroeUse record ID to deleted the record

db.deleteRecord(1); // 刪除 ID = 1 的資料

Java J2ME


Example: RMSimport javax.microedition.rms.*;

public class RmsTests extends MIDlet implements CommandListener {

private RecordStore db;

public RmsTests() {

try {

db = RecordStore.openRecordStore("mydb", true);

System.out.println("SizeAvailable = " + db.getSizeAvailable());

System.out.println("Size = " + db.getSize());

System.out.println("Num of Records " + db.getNumRecords());

System.out.println("Next Record ID " + db.getNextRecordID());

if(db.getNumRecords() == 1) {

byte[] data = db.getRecord(1);

if(data != null) textfield.setString(new String(data));

}


}

public void destroyApp(boolean unconditional) {

byte[] data = this.textfield.getString().getBytes();

try {

if(db.getNumRecords() == 0) db.addRecord(data, 0, data.length);

else db.setRecord(1, data, 0, data.length);


}

}

First time output:SizeAvailable = 996689Size = 48Num of Records 0Next Record ID 1

Second time output:SizeAvailable = 996737Size = 80Num of Records 1Next Record ID 2

Java J2ME


Essential APIs 3. Network

Package: javax.microedition.io

MIDP 1.0 HttpConnection StreamConnection

MIDP 2.0 HttpsConnection SocketConnection

Use Connector to open connectionc = (StreamConnection)Connector.open(“http://localhost/index.html”);

c = (SocketConnection)Connector.open("socket://localhost:4444");

Java J2ME


Example: URL Readerimport javax.microedition.io.*;



import java.io.*;

public class HttpMidlet extends MIDlet {

private TextBox t;

public HttpMidlet() {

try {

String url = "http://java.sun.com:80/j2se/1.5.0/docs/api/java/net/URL.html";

StreamConnection c = null;

InputStream s = null;

StringBuffer b = new StringBuffer();

try {

c = (StreamConnection)Connector.open(url);

s = c.openInputStream();

int ch;

while((ch = s.read()) != -1) b.append((char)ch);

t = new TextBox("hello....", b.toString().substring(0, 1024), 1024, 0);

} finally {

if(s != null) s.close();

if(c != null) c.close();

}


}

public void startApp() { Display.getDisplay(this).setCurrent(t); }

}

Java J2ME


Example: Echo Client MIDletimport javax.microedition.midlet.*;

import javax.microedition.io.*;

import java.io.*;

public class EchoClientMidlet extends MIDlet {

public EchoClientMidlet() {

try {

SocketConnection sc = (SocketConnection)Connector.open("socket://localhost:4444");

sc.setSocketOption(SocketConnection.LINGER, 5);

InputStream is = sc.openInputStream();

OutputStream os = sc.openOutputStream();

os.write("hello\n".getBytes());

int ch = 0;

while(ch != -1) System.out.print((char)is.read());

is.close();

os.close();

sc.close();


}

public void startApp() {}

public void pauseApp() {}

public void destroyApp(boolean unconditional) {}

}

Output:hello

Java J2ME


練習： Monty Hall

1. 使用 MIDlet

2. 可選 3 ~6 個門3. 按鍵 1~6表示要打開門的編號4. 某個門有寶藏，找到時，獲得獎金，且全部的門都要打開 (贏 )

5. 某個門裡面是炸彈，打開時立刻結束遊戲 (輸 )

6. 獎金：門的數量 *100。第一次開門就找到寶藏，可以全拿。每多開一次門，獎金就會減半。看到提示炸彈訊息時，獎金也會減半。獎金可以累計，但不能低於 0

7. (進階 +10)必須防止畫面閃爍8. (進階 +10)顯示動畫9. (進階 +10)播放音效

Java J2ME


練習： Calculator

1. 使用 MIDlet

2. 提供整數的 "加法、減法、乘法、除法 "。輸入數值最多 8位數3. 加減乘除都是立即運算，不需要管四則運算4. 運算過程若發生錯誤，要顯示錯誤訊息。如 overflow 、除數為

0、輸入過大的數等等5. 按鍵對應： 0~9, # 清除 , 上下左右對應到 +,-,*,/

6. (進階 +10) 支援 M+, M-, Mr, Mc 的功能7. (進階 +10)支援小數運算8. (進階 +10)* 鍵連按切換 +, -, *, /

Java J2ME


Introduction to Java Programming

謝謝捧場http://www.csie.nctu.edu.tw/~tsaiwn/java/

蔡文能

交通大學資訊工程系蔡文能 第1頁第1頁 programming in java j2me 汪益賢 蔡文能...

Documents

交通大學資訊工程系蔡文能第1頁第1頁 programming in java j2me 汪益賢蔡文能...