保存一个更新的对象

调用PersistentObject的setContents(),然后调用commit()方法保存一个更新的对象

synchronized(store) {     store.setContents(_data);     store.commit(); }

注: 当你做出改变时,同步一个持久对象,这样其他的线程在同一时间就不能做出改变.

获取一个对象

为了获取最近保存的对象,调用_data.lastElement().

public void run() { synchronized(store) {     _data = (Vector)store.getContents();     if (!_data.isEmpty()) { RestaurantInfo info = (RestaurantInfo)_data.lastElement();     namefield.setText(info.getElement(RestaurantInfo.NAME));     addressfield.setText(info.getElement(RestaurantInfo.ADDRESS));     phonefield.setText(info.getElement(RestaurantInfo.PHONE));     specialtyfield.setText(info.getElement(            RestaurantInfo.SPECIALTY));      }     } }

代码实例

本实例描述了如何创建一个应用程序,它允许用户存储一个关于喜爱的餐厅信息.

本实例也允许用户保存多个餐厅的信息,并且可以查看最新保存的餐厅信息.

---

 

例: Restaurants.java

/* Restaurants.java

* Copyright (C) 2004-2005 Research In Motion Limited.

*/

package com.rim.samples.docs.restaurants;

import net.rim.device.api.ui.*;

import net.rim.device.api.ui.component.*;

import net.rim.device.api.ui.container.*;

import net.rim.device.api.system.*;

import net.rim.device.api.util.*;

import java.util.*;

import net.rim.device.api.i18n.*;

import net.rim.blackberry.api.invoke.*;

import net.rim.blackberry.api.browser.*;

import com.rim.samples.docs.baseapp.*;

import com.rim.samples.docs.resource.*;

 

public class Restaurants extends BaseApp

             implements RestaurantResource,KeyListener, TrackwheelListener {

    private AutoTextEditField namefield;

    private AutoTextEditField addressfield;

    private EditField phonefield;

    private EditField websitefield;

    private EditField specialtyfield;

    private static Vector _data;

    private static PersistentObject store;

    private static ResourceBundle _resources;

    private MenuItem saveItem = new MenuItem(_resources.getString(MENUITEM_SAVE), 110, 10) {

       public void run() {

           RestaurantInfo info = new RestaurantInfo();

           info.setElement(RestaurantInfo.NAME, namefield.getText());

           info.setElement(RestaurantInfo.ADDRESS, addressfield.getText());

           info.setElement(RestaurantInfo.PHONE, phonefield.getText());

           info.setElement(RestaurantInfo.WEBSITE, phonefield.getText());

           info.setElement(RestaurantInfo.SPECIALTY,

                  specialtyfield.getText());

           _data.addElement(info);

           synchronized(store) {

              store.setContents(_data);

              store.commit();

              }

           Dialog.inform(_resources.getString(APP_SUCCESS));

           namefield.setText(null);

           addressfield.setText(null);

           phonefield.setText("");

           websitefield.setText("");

           specialtyfield.setText("");

           }

       };

      

       private MenuItem getItem = new MenuItem(_resources.getString(MENUITEM_GET), 110, 11) {

           public void run() {

              synchronized(store) {

                  _data = (Vector)store.getContents();

                  if (!_data.isEmpty()) {

                     RestaurantInfo info = (RestaurantInfo)_data.lastElement();

                     namefield.setText(info.getElement(RestaurantInfo.NAME));

                     addressfield.setText(info.getElement(RestaurantInfo.ADDRESS));

                     phonefield.setText(info.getElement(RestaurantInfo.PHONE));

                     websitefield.setText(info.getElement(RestaurantInfo.WEBSITE));

                     specialtyfield.setText(info.getElement(RestaurantInfo.SPECIALTY));

                     }

                  }

              }

           };

          

           private MenuItem phoneItem = new MenuItem(_resources.getString(MENUITEM_PHONE), 110, 12) {

              public void run() {

                  synchronized(store) {

                     String phoneNumber = phonefield.getText();

                     if ( phoneNumber.length() == 0) {

                         Dialog.alert(_resources.getString(ALERT_NO_PHONENUMBER));

                         }

                     else {

                         PhoneArguments call =

                            new PhoneArguments(PhoneArguments.ARG_CALL, phoneNumber);

                         Invoke.invokeApplication(Invoke.APP_TYPE_PHONE, call);

                         }

                     }

                  }

              };

             

              private MenuItem browserItem =

                  new MenuItem(_resources.getString(MENUITEM_BROWSER), 110, 12) {

                  public void run() {

                     synchronized(store) {

                         String websiteUrl = websitefield.getText();

                         if (websiteUrl.length() == 0) {

                            Dialog.alert(_resources.getString(ALERT_NO_WEBSITE));

                            }

                         else {

                            BrowserSession visit = Browser.getDefaultSession();

                            visit.displayPage(websiteUrl);

                            }

                         }

                     }

                  };

                 

                  static {

                     _resources = ResourceBundle.getBundle(

                            RestaurantResource.BUNDLE_ID,

                            RestaurantResource.BUNDLE_NAME);

                     store = PersistentStore.getPersistentObject(0xdec6a67096f833cL);

                    

                     // Key is hash of test.samples.restaurants.

                     synchronized (store) {

                         _data = (Vector)store.getContents();

                         if (_data == null) {

                            _data = new Vector();

                            store.setContents( _data );

                            store.commit();

                            }

                         }

                     }

                  public static void main(String[] args) {

                     Restaurants app = new Restaurants();

                     app.enterEventDispatcher();

                     }