android 数据库工具类MyDbHelper
package com.tdd.db.util;

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

public class MyDbHelper {
    public static final String KEY_TITLE = "title";    //数据表字段
    public static final String KEY_BODY = "body";    //数据表字段
    public static final String KEY_ROWID = "_id";    //数据表字段

    private DatabaseHelper mDbHelper;    //SQLiteOpenHelper实例对象
    private SQLiteDatabase mDb;    //数据库实例对象
   
    //数据表创建语句
    private static final String DATABASE_CREATE  = "create table notes (_id integer primary key autoincrement, "
                    + "title text not null, body text not null);";

    private static final String DATABASE_NAME = "data";    //数据库名
    private static final String DATABASE_TABLE = "notes";    //数据库表名
    private static final int DATABASE_VERSION = 2;    //数据库版本号

    private final Context mCtx;    //上下文实例

    private static class DatabaseHelper extends SQLiteOpenHelper {    //数据库辅助类
        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }
        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(DATABASE_CREATE);
        }
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS notes");
            onCreate(db);
        }
    }

    /**
     * Constructor - takes the context to allow the database to be opened/created
     *
     * @param ctx the Context within which to work
     */
    public MyDbHelper(Context ctx) {
        this.mCtx = ctx;
    }

    /**
     * Open the notes database. If it cannot be opened, try to create a new instance of the database.
* If it cannot be created, throw an exception to signal the failure
     *
     * @return this (self reference, allowing this to be chained in an initialization call)
     * @throws SQLException if the database could be neither opened or created
     */
    public MyDbHelper open() throws SQLException {
        mDbHelper = new DatabaseHelper(mCtx);
        mDb = mDbHelper.getWritableDatabase();
        return this;