操作数据库（增删改查）

package com.example.Caozuo;

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

import com.example.day_3sqteshu.Chuangjianshujuku;

public class Caozuo {



    private SQLiteDatabase sq;
    public Caozuo(Context context){
        Chuangjianshujuku chuangjian = new Chuangjianshujuku(context);
        sq = chuangjian.getWritableDatabase();

    }
    //添加
    public boolean add(String name, String arg){
        //写数据用的
        ContentValues values = new ContentValues();
        values.put("name", name);
        values.put("aeg", arg);
        //存的数据存到数据库
        long chuandi = sq.insert("user", null, values);
        if (chuandi != -1){
            return true;
        }else {
            return false;
        }
    }

    //修改
    public boolean gai(String name, int id){
        ContentValues values = new ContentValues();
        values.put("name", name);
        int chuandi = sq.update("user", values, "id = ?", new String[]{String.valueOf(id)});
        if (chuandi >0) {
            return true;
        }else {
            return false;
        }
    }

    //删除
    public boolean shanchu(int id){
        int chuandi = sq.delete("user", "id = ?", new String[]{String.valueOf(id)});
        if (chuandi > 0) {
            return true;
        }else {
            return false;
        }
    }
    //查询+事物
    public String chaxunquan(){

        try {
            //Cursor游标
            Cursor cursor = sq.query(false, "user", null, null, null, null, null, null, null);

            //封装对象的容器
            StringBuffer buffer = new StringBuffer();

            while (cursor.moveToNext()) {

                //得到数据
                String name = cursor.getString(cursor.getColumnIndex("name"));
                String arg  = cursor.getString(cursor.getColumnIndex("arg"));
                //封装对象
                buffer.append("姓名: "+name+" 年龄 : "+arg+"\n");
            }
            //返回封装对象toString方法
            return buffer.toString();
        }catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}