mobilememo.java

手机日记本的设计原理与关键技术 调试环境：Win XP；jdk1.5＋j2me

import java.util.*;
import java.lang.System;

import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.microedition.rms.RecordComparator;
import javax.microedition.rms.*;

public class MobileMemo extends MIDlet implements CommandListener {

	private final String RS_NAME = "memos";
	
	// Screens 
	private Display display;
	private Form inputForm;
	private List list;
	private TextBox memoText;
	
	// Command group
	private Command add = new Command("添加", Command.OK, 1);
	private Command show = new Command("显示", Command.OK, 1);
	private Command ok = new Command("保存", Command.OK, 1);
	private Command delete = new Command("删除", Command.OK, 1);
	
	// Memos
	private Memo currentMemo;
	private Vector memos;
	
	/**
	 * Constructor
	 */
	public MobileMemo() {
		display = Display.getDisplay(this);
		memos = new Vector();
		
		// Generates the memo list 
		initilizeList();
		
		// Generates the Memo screen
		initilizeMemoText();
		
	}

	/**
	 // 启动MIDlet
	 */
	protected void startApp() throws MIDletStateChangeException {

		// 从记录存储中读取信息
		reloadFromRSM();
		// 转到日记列表画面
		display.setCurrent(list);
	}
	/**
	 * 从记录存储中更新信息
	 */
	public void reloadFromRSM() {
		memos.removeAllElements();
		
		// Gets records
		RecordStore rs = null;
		RecordEnumeration re = null;
		try {
			rs = RecordStore.openRecordStore(RS_NAME, true);
                        //列举记录
			re=rs.enumerateRecords(null, null, true);
                        //re=rs.enumerateRecords(null,new TestComparator(), true);
			//取得记录
			while (re.hasNextElement()) {
				int id = re.nextRecordId();// Gets the record ID
				byte[] data = rs.getRecord(id);// Gets records
				Memo memo = new Memo(data);// Generates memos
				memo.setRecId(id);// * Sets the record ID
				memos.addElement(memo);// Adds memos
			}
			
		} catch (Exception e) {
		} finally {
			// Destroys the RecordEnumeration 
			if (re != null) {
				try {
					re.destroy();
				} catch (Exception e) {
				}
			}
			// Closes the record store
			if (rs != null) {
				try {
					rs.closeRecordStore();
				} catch (Exception e) {
				}
			}
		}

		// 更新日记列表
		initilizeList();
                               for (int i = 0; i < memos.size(); i++) {
		  Memo memo = (Memo) memos.elementAt(i);
                                  //取出日记的date，利用Calendar转换成年月日，并添加到list中。
                                  Calendar Now = Calendar.getInstance();
                                  Now.setTime(memo.getDate());
                                  String year = String.valueOf(Now.get(java.util.Calendar.YEAR));
                                  String month = String.valueOf(Now.get(java.util.Calendar.MONTH) + 1);
                                  String day = String.valueOf(Now.get(java.util.Calendar.DATE));		  
                                  list.append(year+"年"+month+"月"+day+"日", null);                                  
		}

	}

	/*
	 * 初始化日记列表
	 */
	private void initilizeList() {
		list = new List("日记列表", List.EXCLUSIVE);
		list.addCommand(show);
		list.addCommand(add);
		list.setCommandListener(this);
	}

	/**
	 * 初始化日记内容
	 */
	private void initilizeMemoText() {
		memoText = new TextBox("日记", "", 100, TextField.ANY);
		memoText.addCommand(ok);
		memoText.addCommand(delete);
		memoText.setCommandListener(this);
	}

	protected void pauseApp() {}

	
	protected void destroyApp(boolean bool) throws MIDletStateChangeException {}

	
	public void commandAction(Command c, Displayable d) {
		if (d == list) {
			if (c == add) {
				// Creates a new memo
				currentMemo = createNewMemo();
			} else if (c == show) {
				// Gets a memo
				int index = list.getSelectedIndex();
				if(index == -1)return;
				currentMemo = (Memo) memos.elementAt(index);
			}
			
			// Moves to the Memo screen 
			memoText.setString(currentMemo.getContent());
			display.setCurrent(memoText);
		} else if (d == memoText) {
			if (c == ok) {
				// 保存日记内容
				currentMemo.setContent(memoText.getString());
				writeMemo(currentMemo);
			} else if (c == delete) {
				//删除日记
				deleteMemo(currentMemo);
			}

			// 转到日记列表画面
			reloadFromRSM();
			display.setCurrent(list);
		}
	}

	/**
	 * 添加新日记
	 */
	public Memo createNewMemo() {
		Memo memo = new Memo();
		return changeMemoToRMS(memo, add);
	}

	/**
	 *保存日记
	 */
	public void writeMemo(Memo memo) {
		changeMemoToRMS(memo, ok);
	}

	/**
	 * 删除日记
	 */
	public void deleteMemo(Memo memo) {
		changeMemoToRMS(memo, delete);
	}

	/**
	 * 更新日记存储
	 */
	private Memo changeMemoToRMS(Memo memo, Command c) {
		RecordStore rs = null;
		try {
			rs = RecordStore.openRecordStore(RS_NAME, true);
			// 更新记录存储
			if (c == ok) { // 编辑状态时的保存
				int id = memo.getRecId();
				rs.setRecord(id, memo.toBytes(), 0, memo.toBytes().length);
			} else if (c == delete) { //删除日记
				int id = memo.getRecId();
				rs.deleteRecord(id);
			} else if (c == add) { //添加新日记
				int id = rs.addRecord(memo.toBytes(), 0, memo.toBytes().length);
				memo.setRecId(id);
			}
		} catch (Exception e) {
		} finally {
			if (rs != null) {
				try {
					rs.closeRecordStore();
					return memo;
				} catch (Exception e) {
				}
			}
		}
		return null;
	}
}