SQLite数据库的使用

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();
			}
	}
}