class DBUtils extends SQLiteOpenHelper{ 　　public DBUtils(Context context, String name, CursorFactory factory,int version) {　　    super(context, "lyj.db", null, 2);//null使用系统自带游标工厂　　} 　　@Override　　public void onCreate(SQLiteDatabase db) {　　    db.execSQL("create table person(personid integer primary key autoincrement,name varchar(20))");　　} 　　@Override　　public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {　　    db.execSQL("alter table person add phone varchar(12) null");　　}}

public void saveDB(Person person) {　　SQLiteDatabase db = dbOpenHelper.getWritableDatabase();　　// 1　　db.execSQL("insert into person(name,age,phone) values (?,?,?)",new Object[] { person.getName(), person.getAge(), person.getPhone() });　　// 2　　ContentValues values = new ContentValues();　　values.put("name", person.getName());　　values.put("age", String.valueOf(person.getAge()));　　db.insert("person", null, values);　　// 如果第3个字段为null就会拼接sql语句为如下：(如确定第3个字段一定不为null,第2字段可写为null)　　// db.insert("person", "name", null); ==>insert into person(name) values(null)　　// db.close(); //本用户本应用使用，关不关不大影响性能} public void deleteDB(Integer id) {　　SQLiteDatabase db = dbOpenHelper.getWritableDatabase();　　db.execSQL("delete from person where personid = ?", new Object[] { id });　　// db.delete("person", "personid = ?", new String[] { id.toString() });} public void updateDB(Person person) {　　SQLiteDatabase db = dbOpenHelper.getWritableDatabase();　　// 1　　db.execSQL("update person set name = ?,age = ?,phone = ? where personid = ?)",new Object[] { person.getName(), person.getAge(), person.getPhone(), person.getId() });　　// 2　　ContentValues values = new ContentValues();　　values.put("name", person.getName());　　values.put("phone", person.getPhone().toString());　　db.update("person", values, "personid = ?", new String[] { String.valueOf(person.getId())});} public Person findDB(Integer id) {　　SQLiteDatabase db = dbOpenHelper.getReadableDatabase();　　// 1　　Cursor cursor = db.rawQuery("select * from person where personid = ?)",new String[] { id.toString() });　　// 2 第2参数：null返回所有字段　　Cursor cursor2 = db.query("person", null, "personid = ?", new String[] { id.toString() },null, null, null);　　if (cursor.moveToFirst()) {// 仅有一条记录　　    String name = cursor.getString(cursor.getColumnIndex("name"));　　    Integer age = cursor.getInt(cursor.getColumnIndex("age"));  　　  // ...  　　  cursor.close();  　　　return new Person(name, age);　　}　　return person;} public List<Person> getScrollData(int offset, int maxSize) {　　List<Person> persons = new ArrayList<Person>();　　SQLiteDatabase db = dbOpenHelper.getReadableDatabase();　　Cursor cursor = db.rawQuery("select * from person limit ?,?)",new String[] { String.valueOf(offset), String.valueOf(maxSize) });　　//按personid 排序 limit 3,5　　Cursor cursor2 = db.query("person", null, null, null, null, null, "personid asc", offset+ "," + maxSize);　　while (cursor.moveToNext()) {  　　 String name = cursor.getString(cursor.getColumnIndex("name")); 　　  Integer age = cursor.getInt(cursor.getColumnIndex("age")); 　　  // ...   　　persons.add(new Person(name, age));　　}　　cursor.close();　　return persons;} // 统计public long getCount() {　　SQLiteDatabase db = dbOpenHelper.getReadableDatabase();　　Cursor cursor = db.rawQuery("select count(*) from person)", null);　　Cursor cursor2 = db.query("person", new String[]{"count(*)"}, null, null, null, null, null);　　if (cursor.moveToFirst()) {// 仅有一条记录　　    long count = cursor.getColumnCount();　　    cursor.close();  　　  return count;　　}　　return 0;} 数据库事务// 事务public void transferAccount() {　　SQLiteDatabase db = dbOpenHelper.getWritableDatabase();　　try { 　　   db.beginTransaction(); 　　   db.execSQL("update person set amount= amount-10 where personid =2"); 　　   db.execSQL("update person set amount= amount+10 where personid =3"); 　　   db.setTransactionSuccessful();　　} finally {　　    //保证结束事务一定执行　　    db.endTransaction();// 默认：回滚(事务标识为true为提交)　　}}