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应用RMS实现用户自动登陆功能解析


  MIDP的子系统Record Management System提供了MIDlet的持久性存储,精通MIDP子系统RMS系列文章对其使用进行了详细介绍。本文讲述如何使用RMS提供的功能实现应用程序的定制功能??自动登陆。
  
  我们的设计思路非常简单,在RecordStore中存储用户的设置和用户的信息(用户名和密码),如果用户选择自动登陆的话,那么下次当用户想联网的时候将跳过登陆界面,系统会从RecordStore中读取用户和密码,经过服务器的验证后转入到适当的界面。我对整个程序进行了简化,我们不进行联网,对信息的存储也都从简,只是为了说明RMS实现应用程序定制的思路,因此给出的代码并没有全面测试和优化。下面是程序的截图
  <center>[[The No.1 Picture.]]</center>
  我们用Account和Preference分别存储用户信息和用户的个性化设置,同样在这两个类中提供序列化的方法,这样方便我们从RecordStore中读取和写入。这里只给出Preference类的代码,Account类似。
  
  package com.j2medev.autologin;
  
  import java.io.*;
  
  public class Preference
  
  {
  
  private boolean autoLogin;
  
  public Preference(boolean _autoLogin)
  
  {
  
  this.autoLogin = _autoLogin;
  
  }
  
  public Preference()
  
  {
  
  }
  
  public void serialize(DataOutputStream dos) throws IOException
  
  {
  
  dos.writeBoolean(autoLogin);
  
  }
  
  public static Preference deserialize(DataInputStream dis)
  
  throws IOException
  
  {
  
  Preference preference = new Preference();
  
  preference.setAutoLogin(dis.readBoolean());
  
  return preference;
  
  }
  
  public boolean isAutoLogin()
  
  {
  
  return autoLogin;
  
  }
  
  public void setAutoLogin(boolean autoLogin)
  
  {
  
  this.autoLogin = autoLogin;
  
  }
  
  }
  
  我们需要一个Model类来处理读取和写入RecordStore数据的逻辑,它也非常简单。为了简化程序我们规定首先写入Account然后写入Preference,这样我们读取的时候只要通过recordID分别为1和2来读取了,在实际使用的时候通常会比较复杂,我们要借助过滤器等查找,可以参考我的基于MIDP1.0实现个人通讯录。
  
  package com.j2medev.autologin;
  
  import javax.microedition.rms.*;
  
  import java.io.*;
  
  public class Model
  
  {
  
  private RecordStore accountStore;
  
  public static final String RNAME = "accountstore";
  
  public Model()
  
  {
  
  try
  
  {
  
  accountStore = RecordStore.openRecordStore(RNAME, true);
  
  } catch (RecordStoreException e)
  
  {
  
  e.printStackTrace();
  
  }
  
  }
  
  public void closeRecordStore()
  
  {
  
  try
  
  {
  
  accountStore.closeRecordStore();
  
  } catch (RecordStoreException e)
  
  {
  
  e.printStackTrace();
  
  }
  
  }
  
  public void saveAccount(Account account)
  
  {
  
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  
  DataOutputStream dos = new DataOutputStream(baos);
  
  try
  
  {
  
  account.serialize(dos);
  
  byte[] data = baos.toByteArray();
  
  accountStore.addRecord(data, 0, data.length);
  
  baos.close();
  
  } catch (IOException e)
  
  {
  
  e.printStackTrace();
  
  } catch (RecordStoreException e)
  
  {
  
  e.printStackTrace();
  
  }
  
  }
  
  public Account getAccount(int recordID)
  
  {
  
  try
  
  {
  
  if (accountStore.getNumRecords() > 0)
  
  {
  
  byte[] data = accountStore.getRecord(recordID);
  
  ByteArrayInputStream bais = new ByteArrayInputStream(data);
  
  DataInputStream dis = new DataInputStream(bais);
  
  Account account = Account.deserialize(dis);
  
  bais.close();
  
  return account;
  
  }
  
  return null;
  
  } catch (IOException e)
  
  {
  
  return null;
  
  } catch (RecordStoreException e)
  
  {
  
  return null;
  
  }
  
  }
  
  public void savePreference(Preference preference)
  
  {
  
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  
  DataOutputStream dos = new DataOutputStream(baos);
  
  try
  
  {
  
  preference.serialize(dos);
  
  byte[] data = baos.toByteArray();
  
  accountStore.addRecord(data, 0, data.length);
  
  baos.close();
  
  } catch (IOException e)
  
  {
  
  e.printStackTrace();
  
  } catch (RecordStoreException e)
  
  {
  
  e.printStackTrace();
  
  }
  
  }
  
  public Preference getPreference(int recordID)
  
  {
  
  try
  
  {
  
  if (accountStore.getNumRecords() > 0)
  
  {
  
  byte[] data = accountStore.getRecord(recordID);
  
  ByteArrayInputStream bais = new ByteArrayInputStream(data);
  
  DataInputStream dis = new DataInputStream(bais);
  
  Preference preference = Preference.deserialize(dis);
  
  bais.close();
  
  return preference;
  
  }
  
  return null;
  
  } catch (IOException e)
  
  {
  
  return null;
  
  } catch (RecordStoreException e)
  
  {
  
  return null;
  
  }
  
  }
  
  }
  
  MIDlet的设计同样很简单,直接给出代码。整个程序的代码可以从这里下载
  
  package com.j2medev.autologin;
  
  import javax.microedition.lcdui.*;
  
  import javax.microedition.midlet.MIDlet;
  
  import javax.microedition.midlet.MIDletStateChangeException;
  
  public class LoginMIDlet extends MIDlet implements CommandListener
  
  {
  
  private Display display;
  
  private Form loginForm;
  
  private Form successForm;
  
  private TextField userName;
  
  private TextField password;
  
  private ChoiceGroup autoLogin;
  
  private Model model;
  
  public static final Command ConnCMD = new Command("Connect", Command.OK, 1);
  
  protected void startApp() throws MIDletStateChangeException
  
  {
  
  initMIDlet();
  
  Preference p = model.getPreference(2);
  
  if (p == null || !p.isAutoLogin())
  
  {
  
  display.setCurrent(loginForm);
  
  } else if (p.isAutoLogin())
  
  {
  
  Account account = model.getAccount(1);
  
  System.out.println("username:" + account.getUsrName() + "password:"
  
  + account.getPassword());
  
  display.setCurrent(successForm);
  
  }
  
  }
  
  public void initMIDlet()
  
  {
  
  model = new Model();
  
  display = Display.getDisplay(this);
  
  loginForm = new Form("LoginForm");
  
  userName = new TextField("username", null, 20, TextField.ANY);
  
  password = new TextField("password", null, 20, TextField.PASSWORD);
  
  autoLogin = new ChoiceGroup("AutoLogin", Choice.MULTIPLE,
  
  new String[] { "remember me" }, null);
  
  loginForm.append(userName);
  
  loginForm.append(password);
  
  loginForm.append(autoLogin);
  
  loginForm.addCommand(ConnCMD);
  
  loginForm.
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