public class DBOpenHelper extends SQLiteOpenHelper {  // 类没有实例化，不能用作父类构造器的参数，必须声明为静态  public DBOpenHelper(Context context, int version) {   super(context, "SQLite.db", null, version);   // 第三个参数CursorFactory指定在执行查询时获得一个游标实例的工厂类，设置为null代表使用系统默认的游标工厂;  }  @Override  public void onCreate(SQLiteDatabase db) {// 数据库第一次被创建的时候被调用，最开始创建数据库时赋的版本号值是0   // SQLiteDatabase用于生成数据库表;数据库存放路径:<package name>/databases/   db.execSQL("create table person(personid integer primary key autoincrement, name varchar(20))");  }  @Override  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// 版本号升级的时候进行调用；如果数据库不存在就不调用   db.execSQL("alter table person add phone varchar(12) null");// 往表中增加一列  } } DBOpenHelper dbOpenHelper = new DBOpenHelper(getContext(), 1); dbOpenHelper.getWritableDatabase();// 会create数据库表or/open数据库表 public class PersonService {  private[b]DBOpenHelper[/b] dbOpenHelper;  public PersonService(Context context) {   super();   this.dbOpenHelper = new DBOpenHelper(context, 2);  }  public void save(Person person) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   // SQLiteDatabase db2 = dbOpenHelper.getWritableDatabase();有缓存的功能，同一个Helper用此方法得到的对象为db;   db.execSQL("insert into person(name,phone) values(?,?)", new Object[] {person.getName(), person.getPhone() });  }  public void delete(Integer id) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   db.execSQL("delete from person where personid=?", new Object[] { id });  }  public void update(Person person) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   db.execSQL("update person set name=?,phone=? where personid=?",new Object[] { person.getName(), person.getPhone(),person.getId() });  }  public Person find(Integer id) {   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   // 如果数据库磁盘空间未满，得到的实例即为getWritableDatabase()得到的对象；因为此方法会调用getWritableDatabase方法；   Cursor cursor = db.rawQuery("select * from person where personid=?",new String[] { id.toString() });   if (cursor.moveToFirst()) {    int personid = cursor.getInt(cursor.getColumnIndex("personid"));    String name = cursor.getString(cursor.getColumnIndex("name"));    String phone = cursor.getString(cursor.getColumnIndex("phone"));    return new Person(personid, name, phone);   }   cursor.close();   return null;  }  /*   * 获取分页数据   */  public List getScollData(int offest, int maxResult) {   List persons = new ArrayList();   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   Cursor cursor = db.rawQuery("select * from person order by personid asc limit ?,?",new String[] { String.valueOf(offest),String.valueOf(maxResult) });   while (cursor.moveToNext()) {    int personid = cursor.getInt(cursor.getColumnIndex("personid"));    String name = cursor.getString(cursor.getColumnIndex("name"));    String phone = cursor.getString(cursor.getColumnIndex("phone"));    persons.add(new Person(personid, name, phone));   }   cursor.close();   return persons;  }  public long getCount() {   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   Cursor cursor = db.rawQuery("select count(*) from person", null);   cursor.moveToFirst();   long result = cursor.getLong(0);   return result;  } } public class OtherPersonService {  private[b]DBOpenHelper[/b] dbOpenHelper;  public OtherPersonService(Context context) {   super();   this.dbOpenHelper = new DBOpenHelper(context, 2);  }  public void save(Person person) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   [b]ContentValues[/b] values = new ContentValues();// ContentValues 专门用于保存字段的值   values.put("name", person.getName());   values.put("phone", person.getPhone());   db.insert("person", null, values);// 第三个参数为字段值,第二个参数为空值字段，如果第三个参数为null  }  public void delete(Integer id) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   db.delete("person", "personid=?", new String[] { id.toString() });  }  public void update(Person person) {   SQLiteDatabase db = dbOpenHelper.getWritableDatabase();   ContentValues values = new ContentValues();   values.put("name", person.getName());   values.put("phone", person.getPhone());   db.update("person", values, "personid=?", new String[] { person.getId().toString() });  }  public Person find(Integer id) {   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   Cursor cursor = db.query("person", null, "personid=?",new String[] { id.toString() }, null, null, null);   if (cursor.moveToFirst()) {    int personid = cursor.getInt(cursor.getColumnIndex("personid"));    String name = cursor.getString(cursor.getColumnIndex("name"));    String phone = cursor.getString(cursor.getColumnIndex("phone"));    return new Person(personid, name, phone);   }   cursor.close();   return null;  }  /*   * 获取分页数据   */  public List getScollData(int offest, int maxResult) {   List persons = new ArrayList();   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   Cursor cursor = db.query("person", null, null, null, null, null,"personid asc", offest + "," + maxResult);                 //db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy, limit);   while (cursor.moveToNext()) {    int personid = cursor.getInt(cursor.getColumnIndex("personid"));    String name = cursor.getString(cursor.getColumnIndex("name"));    String phone = cursor.getString(cursor.getColumnIndex("phone"));    persons.add(new Person(personid, name, phone));   }   cursor.close();   return persons;  }  public long getCount() {   SQLiteDatabase db = dbOpenHelper.getReadableDatabase();   Cursor cursor = db.query("person", new String[] { "count(*)" }, null, null, null, null, null);                 //db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);   cursor.moveToFirst();   long result = cursor.getLong(0);   return result;  } }