技术开发 频道

J2ME综合-关于J2ME中RMS的使用解析

  二、RecordStore的操作。类RMS如下:  

package com.cuilichen.usual;

  import javax.microedition.rms.RecordEnumeration;

  import javax.microedition.rms.RecordStore;

  
public class RMS {

  
public static final int Int1 = 0;//各个字段的默认数值

  
public static final int Int2 = 0;

  
public static final long Long1 = 0;

  
public static final String Str1 = "";

  
public static final String Str2 = "";

  
public static final String Str3 = "";

  
public static boolean addRecord(String name, int int1, int int2,//添加记录

  
long long1, String str1, String str2, String str3, boolean b) {

  
boolean success = false;

  try {

  RecordStore rs
= RecordStore.openRecordStore(name, true);

  Appointment app
= new Appointment(int1, int2, long1, str1, str2,str3, b);

  
//既然str1作为保留字段,我们在这里就要如此操作:例如int1为我们设定的关键字,那么str1 = Integer.toString(int1);

  
byte[] data = app.toBytes();

  rs.addRecord(data,
0, data.length);

  rs.closeRecordStore();

  success
= true;

  } catch (Exception e) {

  e.printStackTrace();

  }

  return success;

  }

  
public static int getNumOfRecords(String name) {//得到RMS中记录的条数

  try {

  RecordStore rs
= RecordStore.openRecordStore(name, true);

  return rs.getNumRecords();

  } catch (Exception e) {

  return
0;

  }

  }

  
public static Appointment[] getRecords(String name) {//取得RMS中的所有记录

  Appointment[] result
= { };

  try {

  RecordStore rs
= RecordStore.openRecordStore(name, false);

  RecordEnumeration re
= rs.enumerateRecords(null, null, false);

  result
= new Appointment[rs.getNumRecords()];

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

  
int j = re.previousRecordId();

  Appointment app
= new Appointment(rs.getRecord(j));

  result
= app;

  
//System.out.println("app["+i+"] "+app.getStr2());

  }

  rs.closeRecordStore();

  } catch (Exception e) {

  }

  return result;

  }

  
public static Appointment getRecord(String name, int j) {//根据记录编号(参数 int j)取得一条记录

  Appointment result
= new Appointment();

  try {

  RecordStore rs
= RecordStore.openRecordStore(name, false);

  RecordEnumeration re
= rs.enumerateRecords(null, null, false);

  result
= new Appointment(rs.getRecord(j));

  rs.closeRecordStore();

  } catch (Exception e) {

  }

  return result;

  }

  
public static int getIndex(String name, String content) {//得到记录号int j,这里需要使用保留字段str1

  RecordStore rs
= null;

  RecordEnumeration re
= null;

  try {

  rs
= RecordStore.openRecordStore(name, false); //open

  re
= rs.enumerateRecords(null, null, false); //enumeration

  
for (int i = 0; i < RMS.getNumOfRecords(name); i++) {

  
int j = re.nextRecordId();

  Appointment app
= new Appointment(rs.getRecord(j));

  
if (app.getStr1().equals(content)) {

  return j;

  }

  }

  } catch (Exception e) {

  }

  return
1;

  }

  
public static boolean setRecord(String name, int id, int int1, int int2,//设置记录号为id的记录

  
long long1, String str1, String str2, String str3, boolean b) {

  
boolean success = false;

  RecordStore rs
= null;

  RecordEnumeration re
= null;

  try {

  rs
= RecordStore.openRecordStore(name, false); //open

  re
= rs.enumerateRecords(null, null, false); //enumeration

  Appointment app
= new Appointment(int1, int2, long1, str1, str2, str3, b);

  
//str1作为保留字段,在这里如此操作:例如若int1为我们设定的关键字,那么str1 = Integer.toString(int1);

  
byte[] data = app.toBytes();

  rs.setRecord(id, data,
0, data.length);

  success
= true;

  rs.closeRecordStore();

  } catch (Exception e) {

  }

  return success;

  }

  }

  在这个类中,我没有将各个Exception向外抛出,一般来说这样作是不合适的,它违背了Java的异常处理机制。但是在我使用这个类的各个J2ME程序中,它是可以胜任的,所以也就没有进行进一步的修改。

  有了以上的两个类和你对RMS的理解,在程序中,你就可以顺畅的使用RMS了。

  比如在MIDlet开始时,如下操作(增加记录):        

protected void startApp() throws MIDletStateChangeException {

  
if (RMS.getNumOfRecords(rsName) = = 0) {//rsName在前面已经声明了。String rsName=“MyRMS”;

  
for (int i = 0; i < 6; i++) {

  RMS.addRecord(rsName, RMS.Int1, i, RMS.Long1,
Integer . toString(i), RMS.Str2, "1234567890123456789",false);

  }

  }它就在RMS中增加了6条记录,其中int1,long1,str2,WroteFlag都没有使用,我们只是使用int2,str1(作为保留字段)和str3。

  }

 

  

0
相关文章