公共代码参考（SQLiteOpenHelper）

package com.fredric.util;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

/*-
 * sqlite数据库操作封装
 */

public class DBHelper extends SQLiteOpenHelper{
    private final static String DB_NAME  = "demo.db";
    private final static String TBL_NAME = "users";
    private static final int DB_VERSION  = 1;
    private final static String CREATE_TBL
        = "CREATE TABLE IF NOT EXISTS users (_id INTEGER PRIMARY KEY AUTOINCREMENT, username VARCHAR, password VARCHAR)";
    private SQLiteDatabase db;

    public DBHelper(Context context, String name, CursorFactory factory,
            int version) {
        super(context, name, factory, version);
    }

    public DBHelper(Context context){
        this(context, DB_NAME, null, DB_VERSION);
    }

    //当数据库第一次被建立的时候被执行，例如创建表,初始化数据等
    @Override
    public void onCreate(SQLiteDatabase db) {
        this.db = db;
        db.execSQL(CREATE_TBL);
    }

    //当数据库需要被更新的时候执行，例如删除表，创建表
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    public void insert(ContentValues values){
        SQLiteDatabase db = getWritableDatabase();
        db.insert(TBL_NAME, null, values);
        db.close();
    }  

    //查询方法
    public Cursor rawQuery(String sql, String[] args){
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery(sql, args);
        return cursor;
    }  

    //删除数据
    public void delete(int id){
        SQLiteDatabase db = getWritableDatabase();
        db.delete(TBL_NAME, "_id=?", new String[]{String.valueOf(id)});
    }  

    //更新数据库的内容
    public void update(ContentValues values, String whereClause, String[] whereArgs){
        SQLiteDatabase db = getWritableDatabase();
        db.update(TBL_NAME, values, whereClause, whereArgs);
    }  

    //关闭数据库
    public void close(){
        if(db != null){
            db.close();
        }
    }
}