Android数据存储之Sqlite数据库的俩种使用方式

一概述

在Android开发中数据存储包括 SharedPreference、文件存储、数据库存储、ContentProvider、网络存储，本文讲述使用Sqlite数据库存储的俩种基本使用方式

1、第一种使用SQL语句实现

编写代码逻辑:使用SqliteOpenHelper类创建一个数据库
创建一个访问数据库增删改查的的接口
封装一个访问数据库增删改查的具实现类

一、DBhelper类

package db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBhelper extends SQLiteOpenHelper {

private static DBhelper mDbHelper = null;

private static final String db_name = "friend.db";
private static final int version = 1;

private static final String CREATE_MESSAGE_TABLE = "create table message_info(_id integer primary key autoincrement," +
"message_id integer,message_userhead text,message_context text,message_imagename text," +
"message_username text,message_time text)";

private static final String DORP_MESSAGE_TABLE = "drop table if exists message_info";

private DBhelper(Context context) {
super(context, db_name, null, version);
}

public static DBhelper getInstance(Context context) {

if (mDbHelper == null) {
synchronized (new Object())
{
if (mDbHelper == null)
{
mDbHelper = new DBhelper(context);
}
}
}
return mDbHelper;
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_MESSAGE_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(DORP_MESSAGE_TABLE);
db.execSQL(CREATE_MESSAGE_TABLE);
}
}

2、封装一个泛型的增删改查的接口

package db;

import java.util.List;

public interface myDbServer<T> {

//插入多条
public void insertMore(List<T> params);
//插入一条
public void insertOne(T params);
//删除一条
public void deleteOne(int  params);
//查询多条
public List<T> getMore();
//查询一条
public  T getOne(int parmas);

}

3、根据存储的JavaBean写实现类

package db;

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

import java.util.LinkedList;
import java.util.List;

import Bean.MessageBean;

public class MessageDao implements myDbServer<MessageBean> {

private DBhelper mDBhelper = null;
private Context context = null;

public MessageDao(Context context) {
this.context = context;
mDBhelper = DBhelper.getInstance(this.context);
}

/**
* 插入多条说说信息
*
* @param params
*/
@Override
public void insertMore(List<MessageBean> params) {

String sql = "insert into message_info(message_id,message_username,message_userhead,message_context," +
"message_time,message_imagename)" + "values(?,?,?,?,?,?)";
SQLiteDatabase db = mDBhelper.getWritableDatabase();
db.delete("message_info",null,null);
for (MessageBean messageBean : params) {
db.execSQL(sql, new Object[]{messageBean.getId(), messageBean.getUserName(), messageBean.getUserHead(),
messageBean.getContext(), messageBean.getTime(), messageBean.getImageName()});
}
db.close();
}

/**
* 插入一条说说信息
*
* @param params
*/
@Override
public void insertOne(MessageBean params) {
String sql = "insert into message_info(message_id,message_username,message_userhead,message_context," +

4000
"message_time,message_imagename)" + "values(?,?,?,?,?,?)";
SQLiteDatabase db = mDBhelper.getWritableDatabase();
db.execSQL(sql, new Object[]{params.getId(), params.getUserName(), params.getUserHead(), params.getContext(),
params.getTime(), params.getImageName()});
db.close();
}

/**
* 删除一条说说信息
*
* @param params
*/
@Override
public void deleteOne(int params) {
String sql = "delete from message_info where message_id  = ? ";
SQLiteDatabase db = mDBhelper.getWritableDatabase();
db.execSQL(sql, new Object[]{params});
db.close();
}

/**
* 获取多条说说信息
*
* @return
*/
@Override
public List<MessageBean> getMore() {

String sql = "select*from message_info";
List<MessageBean> list = new LinkedList<MessageBean>();
SQLiteDatabase db = mDBhelper.getReadableDatabase();
Cursor cursor = db.rawQuery(sql, null);
while (cursor.moveToNext()) {
MessageBean messageBean = new MessageBean();
messageBean.setContext(cursor.getString(cursor.getColumnIndex("message_context")));
messageBean.setImageName(cursor.getString(cursor.getColumnIndex("message_imagename")));
messageBean.setUserHead(cursor.getString(cursor.getColumnIndex("message_userhead")));
messageBean.setUserName(cursor.getString(cursor.getColumnIndex("message_username")));
messageBean.setTime(cursor.getString(cursor.getColumnIndex("message_time")));
messageBean.setId(cursor.getInt(cursor.getColumnIndex("message_id")));
list.add(messageBean);

}
cursor.close();
db.close();
return list;
}

/**
* 获取一条信息
*
* @param parmas
* @return
*/
@Override
public MessageBean getOne(int parmas) {

String SQL = "select*from message_info where message_id = ?";
SQLiteDatabase db = mDBhelper.getReadableDatabase();
Cursor cursor = db.rawQuery(SQL, new String[]{parmas + ""});
MessageBean messageBean = new MessageBean();
messageBean.setContext(cursor.getString(cursor.getColumnIndex("message_context")));
messageBean.setImageName(cursor.getString(cursor.getColumnIndex("message_imagename")));
messageBean.setUserHead(cursor.getString(cursor.getColumnIndex("message_userhead")));
messageBean.setUserName(cursor.getString(cursor.getColumnIndex("message_username")));
messageBean.setTime(cursor.getString(cursor.getColumnIndex("message_time")));
messageBean.setId(cursor.getInt(cursor.getColumnIndex("message_id")));
cursor.close();
db.close();

return messageBean;
}
}

写好以上的类后就可以在访问到网络的数据后存储在数据库中了，把从服务器下载的图片资源可以保存在本地。

sql语句

1、创表语句 ： create table 表名( _id Integer primary key autoincrement,user_id Integer,user_name text,…..字段名 数据类型)

2、删表语句：drop table if exists 表名

3、查询语句：select*from 表名 where id = ?

4、删除语句：delete from 表名 where id = ?

5、插入语句：insert into 表名 （字段名….）values(?,?,?…)

6、更新语句：update 表名 set user_name = ? where id = ?

第二种方式使用SQLiteDatabase中方法

1、db.insert();

2、db.delete();

3、db.update();

4、db.query();