SQLite数据库的使用

xiaodouya33

　　第一步：继承SQLiteOpenHelper
　　


package cn.edu.database;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class MySqliteHelper extends SQLiteOpenHelper{
public MySqliteHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);//factory是null,表示使用CursorFactory是系统自带的
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase arg0) {   //数据库在每一次创建的时候被调用的
// TODO Auto-generated method stub
arg0.execSQL("create table product(id integer primary key autoincrement,name varchar(20),time varchar(20))");//当数据库已经存在在手机上的时候，这个方法SQL语句不会被执行
}
@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {  //当构造方法中的version和以前的数字不一样的时候会调用该方法
// TODO Auto-generated method stub  //该函数是给数据库升级的时候调用的
arg0.execSQL("alter table product add categoryid");
}
}

　　二、数据库的增删改查
　　


package cn.edu.service;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import cn.edu.database.MySqliteHelper;
public class ProductService {
private Context context;
public ProductService(Context context)
{
this.context=context;
}
public void save()
{
MySqliteHelper helper=new MySqliteHelper(context,"test.db",null,1);
SQLiteDatabase db=helper.getWritableDatabase();
db.execSQL("insert into product(name,time) values('12','12')");
db.close();
}
public void delete()
{
MySqliteHelper helper=new MySqliteHelper(context,"test.db",null,1);
SQLiteDatabase db=helper.getWritableDatabase();
db.execSQL("delete product where id=1");
db.close();
}
public void  findById(Integer id)
{
MySqliteHelper helper=new MySqliteHelper(context,"test.db",null,1);
SQLiteDatabase db=helper.getWritableDatabase();
Cursor cursor=db.rawQuery("select * from product where id=?", new String[] {id.toString()});
if(cursor.moveToFirst())
{
System.out.println(cursor.getInt(cursor.getColumnIndex("id")));
System.out.println(cursor.getInt(cursor.getColumnIndex("name")));
System.out.println(cursor.getInt(cursor.getColumnIndex("time")));
}
}
public void update()
{
MySqliteHelper helper=new MySqliteHelper(context,"test.db",null,1);
SQLiteDatabase db=helper.getWritableDatabase();
db.execSQL("update product set name='何' where id=1");
db.close();
}
public void transaction()
{
MySqliteHelper helper=new MySqliteHelper(context,"test.db",null,1);
SQLiteDatabase db =helper.getWritableDatabase();
db.beginTransaction();
try{
db.execSQL("");
db.execSQL("");
db.setTransactionSuccessful();//设置数万的标志为true
}
finally{
db.endTransaction();
}
}
}