数据库 缓存数据

  package helper; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DBHelper extends SQLiteOpenHelper { private static final String TABLENAME="News"; private static final int VERSION = 1; public DBHelper(Context context) { super( context, TABLENAME, null, VERSION ); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL( "create table news(id Integer primary key autoincrement,data text)" ); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } } //dao层 package com.example.dell.ykmoni01; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import com.google.gson.Gson; import java.util.List; import bean.NewsBean; import helper.DBHelper; public class Dao { private SQLiteDatabase db; private static final String TABLENAME = "news"; private static final String DATA = "data"; public Dao(Context context) { DBHelper dbHelper = new DBHelper( context ); db = dbHelper.getWritableDatabase(); } //添加 public long insert(String data){ ContentValues values = new ContentValues(); values.put( DATA, data ); return db.insert( TABLENAME,null, values); } //查询 public List<NewsBean.ResultBean.DataBean> queryAll(){ String dataSql=""; try { Cursor cursor = db.rawQuery("select data from news", null); while(cursor.moveToNext()){ dataSql = cursor.getString( cursor.getColumnIndex( DATA ) ); } NewsBean newsList = new Gson().fromJson( dataSql, NewsBean.class ); return newsList.getResult().getData(); }catch (Exception e){ } return null; } }   package helper; import android.content.Context;