package com.example.utils;import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;/*** Created by Administrator on 2017/12/18.*/public class DbHelper extends SQLiteOpenHelper {//声明数据库的名称private static final String DATABASE_NAME="content.db";//声明版本号private static final int VERSION=1;//重写构造方法private DbHelper(Context context) {super(context, DATABASE_NAME,null, VERSION);}private DbHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {super(context, DATABASE_NAME,null, VERSION);}//创建数据库的方法
    @Overridepublic void onCreate(SQLiteDatabase sqLiteDatabase) {String sql="create table if not exists tb_stu(" +"_id integer primary key," +"sname text," +"sage integer," +"ssex text" +")";sqLiteDatabase.execSQL(sql);sql="insert into tb_stu(sname,sage,ssex) values('Jack',23,'男')";sqLiteDatabase.execSQL(sql);sql="insert into tb_stu(sname,sage,ssex) values('Lucy',22,'女')";sqLiteDatabase.execSQL(sql);}//当数据库发生版本更新的方法
    @Overridepublic void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {String sql="drop table tb_stu";sqLiteDatabase.execSQL(sql);onCreate(sqLiteDatabase);}//单例模式private static DbHelper dbHelper;public static synchronized DbHelper getInstance(Context context){if(dbHelper==null)dbHelper=new DbHelper(context);return dbHelper;}
}

package com.example.utils;import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;/*** Created by Administrator on 2017/12/18.*/public class DbUtils {//声明SQLite数据库
    SQLiteDatabase sdb;//创建构造方法并实例化SQLiteDatabase对象public DbUtils(Context context){sdb=DbHelper.getInstance(context).getReadableDatabase();}//调用SQLiteDatabase对象的 添加 方法进行数据添加，返回值为添加数据行的IDpublic long insert(String tableName, ContentValues values){long id=sdb.insert(tableName,null,values);return id;}//调用SQLiteDatabase对象的 修改 方法进行数据添加，返回值为修改数据行的IDpublic int update(String tableName,ContentValues values,String where,String[] whereArgs){int i=sdb.update(tableName,values,where,whereArgs);return i;}//调用SQLiteDatabase对象的 删除 方法进行数据添加，返回值为删除行public int delete(String tableName,String where,String[] whereArgs){int i=sdb.delete(tableName,where,whereArgs);return i;}//调用SQLiteDatabase对象的 查询 方法进行数据添加，返回值为游标public Cursor query(String tableName,String[] columns,String selection,String[] selectArgs,String groupBy,String having,String orderBy,String limit){Cursor cursor=sdb.query(tableName,columns,selection,selectArgs,groupBy,having,orderBy,limit);return cursor;}
}