recordstoregamedata.java

javaME useful code with the J2ME helpful learning cla

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.rms.*;
import java.io.*;
import java.util.Random;
public class RecordStoreGameData extends MIDlet {
	private RecordStore rs;
private Display display;
	public RecordStoreGameData() {
super();
		display = Display.getDisplay(this);
	}
	protected void startApp() throws MIDletStateChangeException {
		String dbname = "db";//数据仓库的名字
		Form f = new Form("游戏高分榜");
		rs = openRSAnyway(dbname);
		if (rs == null) {
			f.append("Table open fail");
		} else {
			try {
				addData();
				sortData(f);
				rs.closeRecordStore();
deleteRS(dbname);
			} catch (Exception e) {
			}
		}
		display.setCurrent(f);
	}
protected void pauseApp() {
		// TODO Auto-generated method stub
}
protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
	}
public RecordStore openRSAnyway(String rsname) {
		RecordStore rs = null;
	//	名稱大於32 個字元就不接受
		if (rsname.length() > 32)
			return null;
		try {
			rs = RecordStore.openRecordStore(rsname, true);
			return rs;
		} catch (Exception e) {
			return null;
		}
	}
public void addData() {//在数据仓库中增加10条随机数据，删除第4条记录
		try {
			for (int i = 0; i < 10; i++) {
				ByteArrayOutputStream bo = new ByteArrayOutputStream();
				DataOutputStream doSteam = new DataOutputStream(bo);
				doSteam.writeUTF("player" + i);
				Random random = new Random();
				int record = Math.abs(random.nextInt() % 100);
				doSteam.writeInt(record);
				byte data[] = bo.toByteArray();
				rs.addRecord(data, 0, data.length);
				doSteam.close();
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
}
	}
public void sortData(Form form) {//对数据进行排序
		RecordComparator recordComparator = new RecordComparator() {//排序
			public int compare(byte[] firstdata, byte[] seconddata) {
				DataInputStream firstSteam = new DataInputStream(
				new ByteArrayInputStream(firstdata));
				DataInputStream secondSteam = new DataInputStream(
				new ByteArrayInputStream(seconddata));
				int firstRecord = 0;
				int secondRecord = 0;
				try {
					firstSteam.readUTF();//跳过姓名
					firstRecord = firstSteam.readInt();
					secondSteam.readUTF();//跳过姓名
					secondRecord = secondSteam.readInt();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				if (firstRecord == secondRecord) {
					return RecordComparator.EQUIVALENT;
				} else {
					if (firstRecord < secondRecord) {
						return RecordComparator.FOLLOWS;
					} else {
						return RecordComparator.PRECEDES;
					}
				}
			}
		};
		try {
			RecordEnumeration recordEnumeration = rs.enumerateRecords(null,
					recordComparator, false);
			int i = 0;
			while (recordEnumeration.hasNextElement()) {
				byte[] temp = recordEnumeration.nextRecord();
				DataInputStream stream = new DataInputStream(
						new ByteArrayInputStream(temp));
				if (i < 5) {//只取前五名
					form.append("姓名： " + stream.readUTF() + "  ");
					form.append("得分： " + stream.readInt() + "\n");
				}
				i++;
				stream.close();
			}
		} catch (RecordStoreNotOpenException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvalidRecordIDException e) {
		} catch (RecordStoreException e) {
}
	}
public boolean deleteRS(String rsname) {
		if (rsname.length() > 32)
			return false;
		try {
			RecordStore.deleteRecordStore(rsname);
		} catch (Exception e) {
			return false;
		}
		return true;
	}
}