安卓sqllitehelper 继承SQLiteOpenHelper

package com.example.utils;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;/** *  * 用于存储splist的数据 *  * @author 陈滨 *  */public class DBHelper extends SQLiteOpenHelper {    private final static String DATABASE_NAME = "USERS";//数据库名称    private final static int DATABASE_VERSION = 1;//数据库版本    private final static String TABLE_NAME = "USER_INFO";//数据库表名    private final static String FIELD_ID = "_id";//编号    private final static String FIELD_NAME ="NAME";//名称    private final static String FIELD_PASS="PASS";//密码    private final static String FIELD_HEAD="HEAD";//头像    private  SQLiteDatabase db;//数据    @Override    public void onCreate(SQLiteDatabase arg0) {        // TODO Auto-generated method stub           db = this.getWritableDatabase();           String sql = "Create table %s (%s integer primary key autoincrement,%s text,%s text,%s text);";           sql = String.format(sql, TABLE_NAME, FIELD_ID, FIELD_NAME,FIELD_PASS,FIELD_HEAD);           db.execSQL(sql);    }     /**     * 查询所有的数据根据id排序     * @return     */      public Cursor select() {            db = this.getReadableDatabase();            Cursor cursor = db.query(TABLE_NAME, null, null, null, null, null,                    FIELD_ID);            return cursor;        }       /** 注册的时候调用，返回受影响行数        * @param name 用户名        * @param pass 密码        * @param head 头像地址        * @return        */       public long insert(String name,String pass,String head) {            db = this.getWritableDatabase();            ContentValues cv = new ContentValues();            cv.put(FIELD_NAME, name);            cv.put(FIELD_PASS, pass);            cv.put(FIELD_HEAD, head);            long row = db.insert(TABLE_NAME, null, cv);            return row;        }       /**        * 根据id编号删除一行数据        * @param id 编号        */       public void delete(int id){            db = this.getWritableDatabase();            String where  = FIELD_ID + "= ?";            String[] wherevalue = {Integer.toString(id)};            db.delete(TABLE_NAME, where, wherevalue);        }       /**        *  根据编号来更新用信息        * @param id 编号        * @param name 名称        * @param pass 密码        * @param head 头像        */       public void update(int id,String name,String pass,String head)        {            db = this.getWritableDatabase();            String where  = FIELD_ID + "= ?";            String[] wherevalue = {Integer.toString(id)};            ContentValues cv = new ContentValues();            cv.put(FIELD_NAME, name);            cv.put(FIELD_PASS, pass);            cv.put(FIELD_HEAD, head);            db.update(TABLE_NAME, cv, where, wherevalue);        }        /**     * 一个参数的构造方法     * @param context 上下文对象     */    public DBHelper(Context context) {        super(context, DATABASE_NAME, null, DATABASE_VERSION);    }    @Override    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {        // TODO Auto-generated method stub           db=getWritableDatabase();           String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;            db.execSQL(sql);            onCreate(db);    }    public DBHelper(Context context, String name, CursorFactory factory,            int version) {        super(context, name, factory, version);        // TODO Auto-generated constructor stub    }}