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) { // 如果要对数据进行更改，就调用此方法得到用于操作数据库的实例,该方法一读和写方式打开数据库 SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); // 如果只对数据库进行读取，建议使用此方法,但此方法并不是以只读方式打开数据库的。因为该方法内部调用了getWritableDatabase方法 // SQLiteDatabase db2 = dbOpenHelper.getReadableDatabase(); // 用占位符可防止用户输入出现问题 db.execSQL("insert into person (name) values (?)", new Object[] { person.getName() }); // 如果该数据库只被本应用访问，android不建议关闭数据库，为了性能 // 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); } }