RecordMIDlet.java Source code

Introduction

Here is the source code for RecordMIDlet.java

Source

/*
 * Wireless Java 2nd edition Jonathan Knudsen Publisher: Apress ISBN: 1590590775
 */

import java.util.Enumeration;
import java.util.Hashtable;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.lcdui.TextField;
import javax.microedition.midlet.MIDlet;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;

public class RecordMIDlet extends MIDlet implements CommandListener {
    private static final String kUser = "user";

    private static final String kPassword = "password";

    private Preferences mPreferences;

    private Form mForm;

    private TextField mUserField, mPasswordField;

    public RecordMIDlet() {
        try {
            mPreferences = new Preferences("preferences");
        } catch (RecordStoreException rse) {
            mForm = new Form("Exception");
            mForm.append(new StringItem(null, rse.toString()));
            mForm.addCommand(new Command("Exit", Command.EXIT, 0));
            mForm.setCommandListener(this);
            return;
        }

        mForm = new Form("Login");
        mUserField = new TextField("Name", mPreferences.get(kUser), 32, 0);
        mPasswordField = new TextField("Password", mPreferences.get(kPassword), 32, 0);
        mForm.append(mUserField);
        mForm.append(mPasswordField);

        mForm.addCommand(new Command("Exit", Command.EXIT, 0));
        mForm.setCommandListener(this);
    }

    public void startApp() {
        Display.getDisplay(this).setCurrent(mForm);
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {
        // Save the user name and password.
        mPreferences.put(kUser, mUserField.getString());
        mPreferences.put(kPassword, mPasswordField.getString());
        try {
            mPreferences.save();
        } catch (RecordStoreException rse) {
        }
    }

    public void commandAction(Command c, Displayable s) {
        if (c.getCommandType() == Command.EXIT) {
            destroyApp(true);
            notifyDestroyed();
        }
    }
}

class Preferences {
    private String mRecordStoreName;

    private Hashtable mHashtable;

    public Preferences(String recordStoreName) throws RecordStoreException {
        mRecordStoreName = recordStoreName;
        mHashtable = new Hashtable();
        load();
    }

    public String get(String key) {
        return (String) mHashtable.get(key);
    }

    public void put(String key, String value) {
        if (value == null)
            value = "";
        mHashtable.put(key, value);
    }

    private void load() throws RecordStoreException {
        RecordStore rs = null;
        RecordEnumeration re = null;

        try {
            rs = RecordStore.openRecordStore(mRecordStoreName, true);
            re = rs.enumerateRecords(null, null, false);
            while (re.hasNextElement()) {
                byte[] raw = re.nextRecord();
                String pref = new String(raw);
                // Parse out the name.
                int index = pref.indexOf('|');
                String name = pref.substring(0, index);
                String value = pref.substring(index + 1);
                put(name, value);
            }
        } finally {
            if (re != null)
                re.destroy();
            if (rs != null)
                rs.closeRecordStore();
        }
    }

    public void save() throws RecordStoreException {
        RecordStore rs = null;
        RecordEnumeration re = null;
        try {
            rs = RecordStore.openRecordStore(mRecordStoreName, true);
            re = rs.enumerateRecords(null, null, false);

            // First remove all records, a little clumsy.
            while (re.hasNextElement()) {
                int id = re.nextRecordId();
                rs.deleteRecord(id);
            }

            // Now save the preferences records.
            Enumeration keys = mHashtable.keys();
            while (keys.hasMoreElements()) {
                String key = (String) keys.nextElement();
                String value = get(key);
                String pref = key + "|" + value;
                byte[] raw = pref.getBytes();
                rs.addRecord(raw, 0, raw.length);
            }
        } finally {
            if (re != null)
                re.destroy();
            if (rs != null)
                rs.closeRecordStore();
        }
    }
}