学步园

一、单一记录的构造。
    我们在存储记录时可能需要记录很多相似的条目，在这里我们可以把这种结构看成数据库，我们在这一步就是要构造数据库中的一行，即单一记录的构造。程序的源码如下： 
package com.cuilichen.usual; 

import java.io.ByteArrayInputStream;//要使用到的各种输入输出流 
import java.io.ByteArrayOutputStream; 
import java.io.DataInputStream; 
import java.io.DataOutputStream; 
public class Appointment {//单一记录的类名 
 private int int1; // 
 private int int2; // 
 private long long1; 
 private String str1; //str1作为保留字段，记录检索的关键字 
 private String str2; // 
 private String str3; // 
 private boolean WroteFlag; // 
 
public Appointment() { 
} 

public Appointment(int _int1,int _int2,long _long1,String _str1,String _str2,String _str3,boolean _WroteFlag){ 
  this.int1 = _int1; //写入RMS的构造函数 
  this.int2 = _int2; 
  this.long1 = _long1; 
  this.str1 = _str1; 
  this.str2 = _str2; 
  this.str3 = _str3; 
  this.WroteFlag = _WroteFlag; 
} 
public Appointment(byte[] rec) { 
  initAppointmnet(rec); //读取RMS内容的构造函数 
} 
public byte[] toBytes() { //写成字节 
byte[] data = null; 
try { 
  ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
  DataOutputStream dos = new DataOutputStream(baos); 
  dos.writeInt(int1); 
  dos.writeInt(int2); 
  dos.writeLong(long1); 
  dos.writeUTF(str1); 
  dos.writeUTF(str2); 
  dos.writeUTF(str3); 
  dos.writeBoolean(WroteFlag); 
  data = baos.toByteArray(); 
  baos.close(); 
  dos.close(); 
} catch (Exception e) { 
  e.printStackTrace(); 
} 
  return data; 
} 
public void initAppointmnet(byte[] rec) { //从字节读取内容 
  ByteArrayInputStream bais = new ByteArrayInputStream(rec); 
  DataInputStream dis = new DataInputStream(bais); 
  try { 
   int1 = dis.readInt(); 
   int2 = dis.readInt(); 
   long1 = dis.readLong(); 
   str1 = dis.readUTF(); 
   str2 = dis.readUTF(); 
   str3 = dis.readUTF(); 
   WroteFlag = dis.readBoolean(); 
 } catch (Exception e) { 
   e.printStackTrace(); 
 } 
} 
public int getInt1() { //int 
  return int1; 
}
public int getInt2() { 
  return int2; 
}
public long getLong1() { 
  return long1; 
} 
public String getStr1() { //String 
  return str1; 
} 
public String getStr2() { //String 
  return str2; 
} 
public String getStr3() { 
  return str3; 
} 
public boolean getWroteFlag() { //返回写入标志 
  return WroteFlag; 
} 
} 

??????????

    这个类的使用保证了我们在使用流时，内容的写入和输出。当然，就如同数据库表的设计一样，我们可以任意对每一条记录增加或减少字段，在上面的类中我只使用了int1，int2，long1，str1，str2，str3和WroteFlag一共7个字段。

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); 
     
   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[i] = app; 
  } 
   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); 
   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。 
} 
其他的操作也类似，完全可以依靠RMS类实现。今天就介绍这么多，有不明白的地方可以联系我 admin@andyliu.cn