Android之SQLLite

package com.duantl.service;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import com.duantl.domain.Person;

public class PersonService {

 private DBOpenHelper dbOpenHelper;
 private Context context;

 public PersonService(Context context) {
  this.dbOpenHelper = new DBOpenHelper(context);
 }

 public void save(Person person) {
  // 如果要對數據進行更改，就調用此方法得到用於操作數據庫的實例,該方法一讀和寫方式打開數據庫
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  // 如果只對數據庫進行讀取，建議使用此方法,但此方法並不是以只讀方式打開數據庫的。因爲該方法內部調用了getWritableDatabase方法
  // SQLiteDatabase db2 = dbOpenHelper.getReadableDatabase();
  // 用佔位符可防止用戶輸入出現問題
  db.execSQL("insert into person (name) values (?)",
    new Object[] { person.getName() });
  // 如果該數據庫只被本應用訪問，android不建議關閉數據庫，爲了性能
  // db.close();

 }

 public void update(Person person) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  db.execSQL("update person set name=? where personid=?", new Object[] {
    person.getName(), person.getId() });
 }

 public void delete(Integer id) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  db.execSQL("delete from person where personid=?", new Object[] { id
    .toString() });
 }

 public Person find(Integer id) {
  SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
  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"));
   return new Person(personid,name);
  }
  return null;
 }

 public List<Person> getScrollData(Integer offset, Integer maxResult) {
  List<Person> persons = new ArrayList<Person>();
  SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
  Cursor cursor = db.rawQuery("select * from person limit ?,?",
       new String[]{offset.toString(),maxResult.toString()});
  while(cursor.moveToNext()) {
   int personid = cursor.getInt(cursor.getColumnIndex("personid"));
   String name = cursor.getString(cursor.getColumnIndex("name"));
   Person person = new Person(personid, name);
   persons.add(person);
  }  
  cursor.close();
  return persons;
 }

 public long getCount() {
  SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
  Cursor cursor = db.rawQuery("select count(*) from person", null);
  cursor.moveToFirst();
  return cursor.getLong(0);
 }

}