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An example of use of RMS for storing persistent data |
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This Java tip explains RMS Record Management System for storing
persistent data. A record store consists of a collection of records
which will remain persistent. The RMS API abstracts the device-dependent
details of the storage area and access to those details, and it provides
a uniform mechanism to create, destroy, and modify data. This ensures
portability of MIDlets to different devices.
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.rms.*;
import java.io.*;
public class RMSDemo extends MIDlet implements CommandListener {
private Display display;
private RecordStore rs=null;
private Command exit;
private RecordEnumeration re;
private int recordNO;
Form frm;
int index=0;
public RMSDemo() {
display = Display.getDisplay(this);
//Create a RMS
try {
rs= RecordStore.openRecordStore("myRecord",false);
rs.closeRecordStore();
} catch(Exception e) {
System.out.println(e);
}
}
public void startApp() {
frm=new Form("RMSDemo");
exit= new Command("Exit",Command.EXIT,1);
frm.addCommand(exit);
add= new Command("Add",Command.SCREN,1);
frm.addCommand(add);
delete= new Command("Delete",Command.SCREEN,2);
frm.addCommand(delete);
show= new Command("SHOW",Command.SCREEN ,3);
frm.addCommand(show);
frm.setCommandListener(this);
frm.append("#####");
display.setCurrent(frm);
}
public void pauseApp() {
}
public void destroyApp(boolean un) {
}
// Handling commands
public void commandAction(Command cmd,Displayable d) {
if(cmd==add) {
addRecord();
} else
if(cmd==delete) {
removeRecord();
} else
if(cmd==show) {
try {
byte b[]= rs.getRecord(recordNO);
String s= new String(b);
frm.append(s);
} catch(Exception e) {}
}
}
void addRecord() {
try {
rs= RecordStore.openRecordStore("myRecord",false);
index++;
byte b[]=("Record NO "+index).getBytes();
//Adding record to record store
rs.addRecord(b,0,b.length);
rs.closeRecordStore() ;
} catch(Exception e) {
System.out.println(e);
}
}
// Deleting a record
void removeRecord(int recordID) {
try {
rs= RecordStore.openRecordStore("myRecord",false);
rs.deleteRecord(recordID);
index--;
rs.closeRecordStore();
} catch(Exception e) {
System.out.println(e);
}
}
}
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