SQLiteDatabase类2

package com.example.wangye.traintickettest;

import android.content.Context;
import android.database.Cursor;

import java.util.ArrayList;
import java.util.HashMap;

/**
 * Created by wangye on 2018/7/23.
 */

public class UserDAO {
    TrainHelper helper;
    public UserDAO(Context context){
        helper = new TrainHelper(context) ;
    }

    //插入数据
    public String insertUser(String account,String psw){
        if(  chargeUserIsExist(account) ){
            return "该账号已存在";
        }else{
            String sql = "insert into user (account,psw) values (?,?)";
            helper.db.execSQL(sql,new Object[]{account,psw});
            return "注册成功";
        }


    }

    //判断用户信息是否存在
    public boolean chargeUserIsExist(String account){
        String sql = "select * from user where account = ?";
        Cursor cr = helper.db.rawQuery(sql,new String[]{account});
        //判断获取数据的数量
        if(cr.getCount() == 1){
            return true;//存在 不能注册
        }else{
            return false;//不存在 可以注册
        }
    }

    //查询指定账号是否存在 并获取对应的密码
    public ArrayList<HashMap<String,String>> selectUserByAccount(String account){
        ArrayList<HashMap<String,String>> arrayList = new ArrayList<>();
        String sql = "select * from user where account = ?";
        Cursor cr = helper.db.rawQuery(sql,new String[]{account});
        //判断获取数据的数量
        if(cr.getCount() == 1){
            cr.moveToFirst();//把游标对象的游标（指针）强制指向第一条数据
            String psw = cr.getString(cr.getColumnIndex("psw"));
            HashMap<String,String> map = new HashMap<>();
            map.put("psw",psw);
            arrayList.add(map);
        }
        return arrayList;
    }
}