Question

例如，记录库中有三条记录，记录库中记录的结构如下：lastname;firstname;moneyborrowed

我想在LWUIT表中显示这三个记录，我希望它们按lastname列排序。如何实现？

Answer 1

使用

保存

Preferences preferences = new Preferences("mydbname");
preferences.put("key","lastname;firstname;moneyborrowed");
preferences.save();

并使用

进行检索

String val = (string) preferences.get("key");

<强> Preferences.java

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

import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;

public class Preferences {
    private final String mRecordStoreName;

    private final 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();
        }
    }
}

如何根据其中的某个字段对记录库记录进行排序？

1 个答案: