J2ME RMS記錄集存儲管理

本文主要實現對RMS中記錄的增刪改查，考慮到在RMS中ID是不能被重複利用，（例如使用deleteRecord(x)刪除第x條記錄是，在x所在的記錄就不能再被使用，所有添加的數據序號繼續增大），這個數據管理操作帶來不便。

本程序的基本思路如下：刪除第i條記錄，實質上是將第i條記錄的內容改爲其他的特定字符例如“@”，後期遍歷記錄集時如果內容爲“@”則跳過。

程序如下：

import java.util.Vector; import javax.microedition.rms.InvalidRecordIDException; import javax.microedition.rms.RecordStore; import javax.microedition.rms.RecordStoreException; import javax.microedition.rms.RecordStoreFullException; import javax.microedition.rms.RecordStoreNotOpenException; /** * @author WonderCoder * @since 2010-10-30 * @version beta1.0 * 我的收藏記錄集（RMS）存儲管理 */ public class FavourRMS { private RecordStore rs = null; //記錄集名稱 private String RMSNAME = "MyFavour"; //保存記錄集中所有的記錄 private Vector list; //保存記錄集中有效數據(數據內容不爲"@",若內容爲"@"則該數據無效); private Vector urls; public FavourRMS(){ try{ rs = RecordStore.openRecordStore(RMSNAME,true); }catch(Exception ex){ ex.printStackTrace(); } } /** * 添加記錄 * @param url */ public void addDate(String url){ try { byte[] data = url.getBytes(); rs.addRecord(data, 0, data.length); rebulid(); }catch(Exception ex){ ex.printStackTrace(); } } /** * 關閉記錄集 */ public void close(){ try { rs.closeRecordStore(); } catch (RecordStoreNotOpenException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RecordStoreException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * 刪除記錄集 */ public void drop(){ try { RecordStore.deleteRecordStore(RMSNAME); } catch (RecordStoreNotOpenException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidRecordIDException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RecordStoreException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * 獲取所有記錄 * @return */ public String[] getAllDate(){ rebulid(); String[] s = new String[urls.size()]; urls.copyInto(s); return s; } /** * 記錄集是否爲空 * @return */ public boolean isEmpty() { try { return rs.getNumRecords()<1?true:false; } catch (RecordStoreNotOpenException e) { e.printStackTrace(); } return true; } /** * 重構記錄 */ private void rebulid(){ list = new Vector(); urls = new Vector(); String str = null; if(!isEmpty()){ try { int i = rs.getNumRecords(); for(int j=0;j<i;j++){ str = new String(rs.getRecord(j+1)); list.addElement(str); if(!str.endsWith("@")){ urls.addElement(str); } } } catch (RecordStoreNotOpenException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidRecordIDException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RecordStoreException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } /** * 依據數據對應序號刪除記錄 * @param index 有效數據集中序號 */ public void remove(int index){ if(index>-1){ remove(urls.elementAt(index)); } } /** * 根據數據對象刪除記錄 * @param elem 要刪除的數據對象 */ public void remove(Object elem){ if(list!=null){ int index = list.indexOf(elem); if(index>-1) removeItem(index); } } /** * 根據記錄集中的真實序號刪除記錄 * @param index */ private void removeItem(int index){ byte b[] = "@".getBytes(); try { rs.setRecord(index+1, b,0,b.length); } catch (RecordStoreNotOpenException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidRecordIDException 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(); } rebulid(); } /** * 重新打開記錄集 */ public void reopenRecordStore() { try { rs = RecordStore.openRecordStore(RMSNAME, true); }catch(Exception ex){ ex.printStackTrace(); } } /** * 更新記錄 * @param newObj 新記錄 * @param index 被更新的記錄在記錄集中的真實序號 */ public void update(String newObj,int index){ byte[] data = newObj.getBytes(); try { rs.setRecord(index+1, data, 0, data.length); } catch (RecordStoreNotOpenException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidRecordIDException 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(); } } /** * 更新記錄 * @param newObj 新記錄 * @param oldObj 舊記錄 */ public void update(String newObj,String oldObj){ int index = urls.indexOf(oldObj); update(newObj,index); } }

案例程序代碼：

 

import java.util.Random; import javax.microedition.lcdui.Choice; import javax.microedition.lcdui.Command; import javax.microedition.lcdui.CommandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.List; import javax.microedition.midlet.MIDlet; import javax.microedition.midlet.MIDletStateChangeException; public class MyFavour extends MIDlet implements CommandListener{ private Command add; private Command del; private FavourRMS rms; private Display display; private List list; public MyFavour() { display = Display.getDisplay(this); add = new Command("添加",Command.EXIT,1); del = new Command("刪除",Command.EXIT,1); rms = new FavourRMS(); list = new List("選擇類型", Choice.IMPLICIT, rms.getAllDate(), null); rms.reopenRecordStore(); list.addCommand(add); list.addCommand(del); list.setCommandListener(this); display.setCurrent(list); } protected void destroyApp(boolean arg0) throws MIDletStateChangeException { // TODO Auto-generated method stub } protected void pauseApp() { // TODO Auto-generated method stub } protected void startApp() throws MIDletStateChangeException { // TODO Auto-generated method stub } public void commandAction(Command cmd, Displayable arg1) { // TODO Auto-generated method stub if(cmd == add){ Random rad = new Random(); String s = ""+rad.nextInt(100); System.out.println(s); rms.addDate(s); list.append(s, null); } if(cmd == del){ int i = list.getSelectedIndex(); if(i>-1){ rms.remove(i); list.delete(i); } } } }

比較簡單，有不足自出請多多指點。。