一个经典的 JAVA ME 手机程序入门级源码
一个由 Carol Hamer 写的比较有代表性的源码，作者全力推荐，尤其是对于没有 J2ME 开发经验的朋友。自己动手敲出以下贴出的 Hello.java 和 HelloCanvas.java 源码，并运行，用心体会一下。相信你理解了此源码之后，即可步入 J2ME 开发。
注释都在源码里，运行环境自己配，自己动手看运行效果，理解之后，然后动手修改一下源码，J2ME 开发，你可以的！
Hello.java 源码：
package net.frog_parrot.hello;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
/**
* This is the main class of the hello world demo
*
* @author Carol Hamer
*
*/
public class Hello extends MIDlet implements CommandListener {
/**
* The canvas is the region of the screen that has bean alloted to the game
*/
HelloCanvas myCanvas;
/**
* The Command objects apears as buttons.
*/
private Command exitCommand = new Command("Exit",Command.EXIT,99);
/**
* The Command objects apears as buttons.
*/
private Command newCommand = new Command("Toggle Msg",Command.SCREEN,1);
/**
* initialize the canvas and the commands
*/
public Hello() {
myCanvas = new HelloCanvas(Display.getDisplay(this));
myCanvas.addCommand(exitCommand);
myCanvas.addCommand(newCommand);
myCanvas.setCommandListener(this);
}
//--------------------------------
// implementation of MIDlet
/**
* Start the application
*/
protected void startApp() throws MIDletStateChangeException {
myCanvas.start();
}
/**
* This method is called to notify the MIDlet to enter a paused state.
* The MIDlet should use this opportunity to release shared resources.
*/
protected void pauseApp() {
}
/**
* If the MIDlet was using resources,it should release them in this method
*/
protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
}
//-----------------------
// implementation of CommandListener.
/**
* Respond to a command issued on the Canvas
* (either reset or exit)
*/
public void commandAction(Command c, Displayable s) {
if(c == newCommand) {
myCanvas.newHello();
}else if(c == exitCommand) {
try {
destroyApp(false);
notifyDestroyed();
} catch (MIDletStateChangeException e) {
}
}
}
}
HelloCanvas.java 源码：
package net.frog_parrot.hello;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.game.GameCanvas;
/**
* This class represents the region of the screen that has bean alloted to the game
*
* @author Carol Hamer
*
*/
public class HelloCanvas extends GameCanvas {
//------------------------
//fields
/**
* A handle to the screen of the device
*/
Display myDisplay;
/**
* Whether or not the screen should currently display the "Hello world" message.
*/
boolean mySayHello = true;
//-------------------------------
//initialization and game state changes
/**
* Constructor merely sets the display
*/
public HelloCanvas(Display d) {
super(false);
myDisplay = d;
}
/**
* This is called as soon as the application begins
*/
void start() {
myDisplay.setCurrent(this);
repaint();
}
/**
* toggle the hello message
*/
void newHello() {
mySayHello = !mySayHello;
//paint the display
repaint();
}
//------------------------------------
//graphics methods
/**
* clear the screen and display the hello world message if appropriate.
*/
public void paint(Graphics g) {
// x and y are the coordinates of the top corner of the game's dispaly area
int x = g.getClipX();
int y = g.getClipY();
// w and h are are the width and height of the display area:
int w = g.getClipWidth();
int h = g.getClipHeight();
// clear the screen (paint it white):
g.setColor(0xffffff);
g.fillRect(x, y, w, h);
//display the hello world message if appropriate:
if(mySayHello) {
Font font = g.getFont();
int fontHeight = font.getHeight();
int fontWidth = font.stringWidth("Hello World!");
// set the text color to red:
g.setColor(0x00ff0000);
g.setFont(font);
// write the string in the center of the screen:
g.drawString("Hello World!", (w-fontWidth)/2, (h-fontHeight)/2, g.TOP|g.LEFT);
}
}
}
注：本文源码来自于 Carol Hamer 写的 《一步一步学习 midp2.0 编程》，这本书的中译本已经共享至我的 csdn 资源，pdf 格式的，有兴趣的朋友可以去下载下来看看。如果你还徘徊在 J2ME 游戏开发的大门之外，并且找不着比较好的入门资料和源代码，那么这本书就是为不得其门而入的你写的！
