永続的なストアの取り扱い

Question

私はBlackberryで電子メールの種類のアプリケーションに取り組んでいます。 すべてのメールを永続ストアに保存したい。 連絡先のリストも保存する必要があります。

永続ストアを使用してこの種の機能を操作するにはどうすればよいですか？

どのようにデータを保存しますか？

複数のメッセージを保存できますか？

正しくアクセスして画面に表示するにはどうすればよいですか？

以前は永続的な店舗で働いたことがない、 助けてください。

Answer 1

永続ストレージにインデックスがありません。
Persistableオブジェクトの配列を保存および取得できます。一例では
、連絡先永続：

public class Contact implements Persistable{ 
    int mId; String mAdress; String mName;  
    public Contact(int id, String adress, String name){ 
     mId = id; mAdress = adress; mName = name; 
    }  
} 

メール永続：

public class Mail implements Persistable{ 
    String mMessage = null; int mSenderId = -1; int[] mReceiverIdList = null;  
    public Mail(String message, int senderId, int[] receiverIdList){ 
     mMessage = message; mSenderId = senderId; 
     mReceiverIdList = receiverIdList; 
    } 
} 

いくつかのヘルパークラス：

public class PersistentStoreHelper{ 
    static PersistentObject contactStore = PersistentStore 
      .getPersistentObject(0xf140775afcb94f90L); 
    static PersistentObject mailStore = PersistentStore 
    .getPersistentObject(0xd43b0423228ff7c0L); 
    public static void saveContacts(Contact[] contacts){ 
     saveObject(contactStore, contacts); 
    } 
    public static void saveMails(Mail[] mails){ 
     saveObject(mailStore, mails); 
    } 
    public static Contact[] retrieveContacts(){ 
     return (Contact[])retrieveObject(contactStore); 
    } 
    public static Mail[] retrieveMails(){ 
     return (Mail[])retrieveObject(mailStore); 
    } 
    public static void saveObject(PersistentObject store, Object object){ 
     synchronized(store){ 
      store.setContents(object); 
      store.commit(); 
     } 
    } 
    public static Object retrieveObject(PersistentObject store){ 
     Object result = null; 
     synchronized(store){ 
      result = store.getContents(); 
     } 
     return result; 
    } 
} 

と使用のサンプル：

class Scr extends MainScreen implements FieldChangeListener{ 
    ButtonField mBtnInit = null; 
    BasicEditField mInputSenderId = null; 
    BasicEditField mInputReceiverId = null; 
    ButtonField mBtnSearch = null; 
    VerticalFieldManager mMailsList = null; 
    public Scr(){ 
     mBtnInit = new ButtonField("Init Persistenet Storage", 
      ButtonField.CONSUME_CLICK); 
     mBtnInit.setChangeListener(this); 
     add(mBtnInit); 
     mInputSenderId = new BasicEditField("sender id:", "43"); 
     add(mInputSenderId); 
     mInputReceiverId = new BasicEditField("receiver id:", "12"); 
     add(mInputReceiverId); 
     mBtnSearch = new ButtonField("Search", ButtonField.CONSUME_CLICK); 
     mBtnSearch.setChangeListener(this); 
     add(mBtnSearch); 
     mMailsList = new VerticalFieldManager(); 
     add(mMailsList); 
    } 
    public Vector getMailByIds(int senderId, int recepientId){ 
     Vector result = new Vector(); 
     Mail[] mails = PersistentStoreHelper.retrieveMails(); 
     for(int i = 0; i < mails.length; i++) 
      if(mails[ i ].mSenderId == senderId){ 
       int[] receiverIdList = mails[ i ].mReceiverIdList; 
       for(int j = 0; j < receiverIdList.length; j++) 
        if(recepientId == receiverIdList[ j ]) 
         result.addElement(mails[ i ]); 
      } 
     return result; 
    } 
    public void initPersistentStorage(){ 
     // create 100 contacts and save them 
     Contact[] contacts = new Contact[ 100 ]; 
     for(int i = 0; i < 100; i++){ 
      String name = "name" + String.valueOf(i); 
      String adress = name + "@mail.com"; 
      contacts[ i ] = new Contact(i, adress, name); 
     } 
     PersistentStoreHelper.saveContacts(contacts); 
     // create messages from each to every contact and save them 
     Mail[] mails = new Mail[ 10000 - 100 ]; 
     int k = 0; 
     for(int i = 0; i < 100; i++) 
      for(int j = 0; j < 100; j++) 
       if(i != j){ 
        Mail mail = new Mail("Hello!", contacts[ i ].mId, 
         new int[]{ contacts[ j ].mId }); 
        mails[ k ] = mail; 
        k++; 
       } 
     PersistentStoreHelper.saveMails(mails);   
    } 
    public void fieldChanged(Field field, int context){ 
     if(field == mBtnInit) 
      initPersistentStorage(); 
     else if(field == mBtnSearch){ 
      mMailsList.deleteAll(); 
      int senderId = Integer.parseInt(mInputSenderId.getText()); 
      int receiverId = Integer.parseInt(mInputReceiverId.getText()); 
      Contact[] contacts = PersistentStoreHelper.retrieveContacts(); 
      Vector result = getMailByIds(senderId, receiverId); 
      for(int i = 0, cnt = result.size(); i < cnt; i++) 
      { 
       Mail mail = (Mail)result.elementAt(i); 
       String from = "From: " + contacts[ mail.mSenderId ].mName 
         + " <" + contacts[ mail.mSenderId ].mAdress + ">"; 
       String to = "To: "; 
       for(int j = 0; j < mail.mReceiverIdList.length; j++) 
       { 
        int id = mail.mReceiverIdList[ j ]; 
        to += contacts[ id ].mName + " <" 
         + contacts[ id ].mAdress + ">; "; 
       } 
       to = to.substring(0, to.length() - 2); 
       String msg = "Message: " + mail.mMessage; 
       mMailsList.add(new LabelField(from)); 
       mMailsList.add(new LabelField(to)); 
       mMailsList.add(new LabelField(msg)); 
      } 
     } 
    } 
} 

Read BlackBerry Java Application - Core - Development Guide - Persistent Storage
riccomini - code blackberry persistent store