package cn.learn.db.util;

import android.content.context;
import android.database.sqlite.sqlitedatabase;
import android.database.sqlite.sqliteopenhelper;
import android.database.sqlite.sqlitedatabase.cursorfactory;

public class dbhelper extends sqliteopenhelper {

 private final static string db_name ="test.db";//數據庫名
 private final static int version = 1;//版本號

 //自帶的構造方法
 public dbhelper(context context, string name, cursorfactory factory,
   int version) {
  super(context, name, factory, version);
 }

 //為了每次構造時不用傳入dbname和版本號，自己得新定義一個構造方法
 public dbhelper(context cxt){
  this(cxt, db_name, null, version);//調用上面的構造方法
 }

 //版本變更時
 public dbhelper(context cxt,int version) {
  this(cxt,db_name,null,version);
 }

 //當數據庫創建的時候調用
 public void oncreate(sqlitedatabase db) {
  string sql = "create table student(" +
      "id integer primary key autoincrement," +
      "name varchar(20)," +
      "age int)";

  db.execsql(sql);
 }

 //版本更新時調用
 public void onupgrade(sqlitedatabase db, int oldversion, int newversion) {
  string sql  = "update student ....";//自己的update操作
  db.execsql(sql);
 }

}

package cn.learn.db.dao;

import android.content.context;
import android.database.sqlite.sqlitedatabase;
import cn.learn.db.dao.domain.student;
import cn.learn.db.util.dbhelper;

public class studentdao {

 dbhelper helper = null;

 public studentdao(context cxt) {
  helper = new dbhelper(cxt);
 }

 /**
  * 當activity中調用此構造方法，傳入一個版本號時，系統會在下一次調用數據庫時調用helper中的onupgrade()方法進行更新
  * @param cxt
  * @param version
  */
 public studentdao(context cxt, int version) {
  helper = new dbhelper(cxt, version);
 }

 // 插入操作
 public void insertdata(student stu) {
  string sql = "insert into student (name,age)values(?,?)";
  sqlitedatabase db = helper.getwritabledatabase();
  db.execsql(sql, new object[] { stu.name, stu.age });
 }

 // 其它操作

}