J2me 入门路之---3 RecordStore

package com.sa.demo.rs;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.TextBox;
import javax.microedition.lcdui.TextField;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;
import javax.microedition.rms.RecordStoreFullException;
import javax.microedition.rms.RecordStoreNotFoundException;
import javax.microedition.rms.RecordStoreNotOpenException;

public class TestRS2 extends MIDlet implements CommandListener {
private Command exitCommand, addCmd, delCmd, setCmd, getCmd;
private Display display;
private RecordStore rs; // 定义记录存储rs
private TextBox showMsg; // 用于显示操作结果信息
private String msg = ""; // 存放用于文本框显示的信息

public TestRS2() {

display = Display.getDisplay(this);
showMsg = new TextBox("操作信息:", null, 512, TextField.ANY);
exitCommand = new Command("退出", Command.EXIT, 1);
addCmd = new Command("添加记录", Command.SCREEN, 1);
delCmd = new Command("删除记录", Command.SCREEN, 1);
setCmd = new Command("修改记录", Command.SCREEN, 1);
getCmd = new Command("读取记录", Command.SCREEN, 1);
showMsg.addCommand(exitCommand);
showMsg.addCommand(addCmd);
showMsg.addCommand(delCmd);
showMsg.addCommand(setCmd);
showMsg.addCommand(getCmd);
showMsg.setCommandListener(this);
if (OpenRS("myRS"))
msg += "记录存储myRS打开成功";
else
msg += "记录存储myRS打开失败";
}

private boolean OpenRS(String rsName) {
// TODO Auto-generated method stub
try {
rs = RecordStore.openRecordStore("rsName", true);
return true;
} catch (RecordStoreFullException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
} catch (RecordStoreNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
} catch (RecordStoreException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}

}

protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
// TODO Auto-generated method stub
if (CloseRS())
System.out.println("记录存储myRS关闭成功");
else
System.out.println("记录存储myRS关闭失败");
}

private boolean CloseRS() {
// TODO Auto-generated method stub
return false;
}

protected void pauseApp() {
// TODO Auto-generated method stub

}

protected void startApp() throws MIDletStateChangeException {
// TODO Auto-generated method stub
showMsg.setString(msg);
display.setCurrent(showMsg);
}

public void commandAction(Command c,Displayable d) {
int recId;
if (c == exitCommand) {
try {
destroyApp(false);
} catch (MIDletStateChangeException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
notifyDestroyed();
}
else if (c == addCmd) {
if ((recId = AddRec()) != -1)
msg = "记录添加成功,记录号为 " + recId;
else
msg = "记录添加失败";
showMsg.setString(msg);
}
else if (c == delCmd) {
if ((recId = DelRec()) != -1)
msg = "记录删除成功,记录号为 " + recId;
else
msg = "记录删除失败";
showMsg.setString(msg);
}
else if (c == setCmd) {
if ((recId = SetRec()) != -1)
msg = "记录修改成功,记录号为 " + recId;
else
msg = "记录修改失败";
showMsg.setString(msg);
}
else if (c == getCmd) {
msg = GetRec();
showMsg.setString(msg);
}
}

public int DelRec() {
int id, num;
try {
id = rs.getNextRecordID();
num = rs.getNumRecords();
}
catch (RecordStoreException e) {
        return -1;
}
if (num >0) {
for (int i=id-1; i>0; i--) {
try {
rs.deleteRecord(i);
return i;
}
catch (RecordStoreException e) { }
}
}
        return -1;
    }

private int AddRec() {
// TODO Auto-generated method stub
int id = -1;
int recID = -1;
try {
id = rs.getNextRecordID();//添加记录 返回记录的位置

} catch (RecordStoreNotOpenException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (RecordStoreException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String data = "Data of Record :"+id;
byte[] rec = data.getBytes();
try {
recID = rs.addRecord(rec, 0, rec.length);//插入数据。

} catch (RecordStoreNotOpenException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (RecordStoreFullException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (RecordStoreException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return recID ;
}
public int SetRec() {
int id, num;
try {
id = rs.getNextRecordID();
num = rs.getNumRecords();
}
catch (Exception e) {
        return -1;
}
        String rec;
byte [] data;
if (num >0) {
for (int i=id-1; i>0; i--) {
rec = "Modified Data of Record " + i;
data = rec.getBytes();
try {
rs.setRecord(i, data, 0, data.length);
return i;
}
catch (RecordStoreException e) { }
}
}
        return -1;
    }
    // 显示所有记录
    public String GetRec() {
int id, num;
try {
id = rs.getNextRecordID();
num = rs.getNumRecords();
}
catch (RecordStoreException e) {
        return null;
}
        String rec = "记录存储中共有" + num + "条记录:";
byte [] data = null;
if (num >0) {
for (int i=1; i<id; i++) {
try {
int size = rs.getRecordSize(i);
if (data == null || data.length < size) {
data = new byte[size];
}
rs.getRecord(i, data, 0);
rec += "\n" + new String(data,0,size);
}
catch (RecordStoreException e) {
}
}
}
        return rec;
    }
// 打开（创建）记录存储
}
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