test.java

Eclipse开发J2ME[进制转换的例子]。图文教会你

//创作者：杨明
//email:[e-mail]

package com.strive4all;

import javax.microedition.midlet.MIDlet;

import javax.microedition.lcdui.*;

public final class Test extends MIDlet implements CommandListener {

	/** The number of characters in numeric text field. */

	private static final int NUM_SIZE = 20;
	private final Command exitCmd = new Command("退出", Command.EXIT, 2);
	private final Command startCmd = new Command("开始", Command.SCREEN, 1);

	/** A text field to keep the first argument. */
	private final TextField originalNum = new TextField(null, "", NUM_SIZE,
			TextField.DECIMAL);

	/** A text field to keep the second argument. */
	private final TextField result = new TextField("结果", "", NUM_SIZE,
			TextField.UNEDITABLE);

	/** A choice group with available operations. */
	private final ChoiceGroup choice = new ChoiceGroup("", ChoiceGroup.POPUP,

	new String[] { "十进制->二进制", "二进制->十进制", }, null);


	private final Alert alert = new Alert("Error", "", null, AlertType.ERROR);

	/** Indicates if the application is initialized. */
	private boolean isInitialized = false;

	protected void startApp() {
		if (isInitialized) {
			return;
		}

		Form mainForm = new Form("进制转换(杨明)");
		mainForm.append(originalNum);
		mainForm.append(choice);
		mainForm.append(result);
		mainForm.addCommand(exitCmd);
		mainForm.addCommand(startCmd);
		mainForm.setCommandListener(this);
		Display.getDisplay(this).setCurrent(mainForm);
		alert.addCommand(new Command("返回", Command.SCREEN, 1));
		isInitialized = true;
	}

	protected void destroyApp(boolean unconditional) {
	}

	protected void pauseApp() {
	}

	public void commandAction(Command c, Displayable d) {
		if (c == exitCmd) {
			destroyApp(false);
			notifyDestroyed();
			return;
		}

		int flag=0;
		int n1=0;
		try {
			n1 = getNumber(originalNum, "First");
			switch (choice.getSelectedIndex()) {
			case 0:	flag=10;
					break;
			case 1:	flag=2;
					break;
			default:
			}
		} catch (NumberFormatException e) {
			return;
		} catch (ArithmeticException e) {
			alert.setString("Divide by zero.");
			Display.getDisplay(this).setCurrent(alert);
			return;
		}

		String res_str=Integer.toString(n1);
		if (res_str.length() > result.getMaxSize()) {
			result.setMaxSize(res_str.length());
		}
		if(flag==10){
			res_str=String.valueOf(Integer.toBinaryString(Integer.parseInt(res_str)));
		}
		if(flag==2){
			res_str=String.valueOf(Integer.parseInt(res_str,2));
		}
		result.setString(res_str);
	}

	private int getNumber(TextField t, String type)
			throws NumberFormatException {
		String s = t.getString();
		if (s.length() == 0) {
			alert.setString("No " + type + " Argument");
			Display.getDisplay(this).setCurrent(alert);
			throw new NumberFormatException();
		}

		int n;
		try {
			n = Integer.parseInt(s);
		} catch (NumberFormatException e) {
			alert.setString(type + " argument is out of range.");
			Display.getDisplay(this).setCurrent(alert);
			throw e;
		}
		return n;
	}
}