Android GreenDao 3.0使用实例讲解

GreenDao简介

greenDAO是一个对象关系映射（ORM）的框架，能够提供一个接口通过操作对象的方式去操作关系型数据库，它能够让你操作数据库时更简单、更方便。

如何使用GreenDao 3.0

(1).新建Android项目工程，在工程目录的build.gradle中添加
dependencies { classpath ‘org.greenrobot:greendao-gradle-plugin:3.1.0’}
(2).在module的build.gradle文件中添加依赖
apply plugin: ‘org.greenrobot.greendao’
dependencies {compile ‘org.greenrobot:greendao:3.2.0’}
在android{}中添加
greendao
{
schemaVersion 1
targetGenDir ‘src/main/java/’
}
其中schmaVersion 表示数据库的版本，targetGenDir 表示编译后DaoMaster 、DaoSession、Dao文件的生成目录。

创建一个实体类：

@Entitypublic class Cars{   //注意：通过@Property()这个注解定义我外部数据库的字段名才能解决   //否则在插入数据的时候会报相关的错误。    @Property(nameInDb = "id")    @Id(autoincrement = true)    private long id;    @Property    private String car_name;    @Property    private String car_price;    @Property    private String car_factory;}

编译后自动生成三个类文件，如图所示：

创建一个数据库管理类，用于数据的插入，更新，删除，查询。代码如下：

import android.content.Context;import android.database.sqlite.SQLiteDatabase;import org.greenrobot.greendao.query.QueryBuilder;import java.util.List;/** 1. 数据库管理类 2. Created by admin on 2017/6/24. */public class DBManager{    private static final String DB_NAME = "dao_db";    private static DBManager instance;    private DaoMaster.DevOpenHelper openHelper;    private Context mContext;    public DBManager(Context context)    {        this.mContext = context;        openHelper = new DaoMaster.DevOpenHelper(context, DB_NAME, null);    }    public static DBManager getInstance(Context context)    {        if (instance == null)        {            synchronized (DBManager.class)            {                if (instance == null)                {                    instance = new DBManager(context);                }            }        }        return instance;    }    /**     * 插入一条数据     * @param car     */    public void insertUser(Cars car)    {        DaoMaster daoMaster = new DaoMaster(getWritableDatabase());        DaoSession daoSession = daoMaster.newSession();        CarsDao carsDao = daoSession.getCarsDao();        carsDao.insert(car);    }    /**     * 插入用户集合     *     * @param cars     */    public void insertUserList(List<Cars> cars)    {        if (cars == null || cars.isEmpty())        {            return;        }        DaoMaster daoMaster = new DaoMaster(getWritableDatabase());        DaoSession daoSession = daoMaster.newSession();        CarsDao carsDao = daoSession.getCarsDao();        carsDao.insertInTx(cars);    }    public void update()    {        List<Cars> carList = query();        for (Cars car : carList)        {            if (car.getId() == 3)            {                car.setCar_price(88888888 +"");                updates(car);            }        }    }    public void updates(Cars cars)    {        DaoMaster daoMaster = new DaoMaster(getWritableDatabase());        DaoSession daoSession = daoMaster.newSession();        CarsDao carsDao = daoSession.getCarsDao();        carsDao.update(cars);    }    public void delete()    {        List<Cars> userList = query();        for (Cars car : userList)        {            if (car.getId() == 4)            {                delete(car);            }        }    }    public void delete(Cars cars)    {        DaoMaster daoMaster = new DaoMaster(getWritableDatabase());        DaoSession daoSession = daoMaster.newSession();        CarsDao carsDao = daoSession.getCarsDao();        carsDao.delete(cars);    }    public List<Cars> query()    {        DaoMaster daoMaster = new DaoMaster(getWritableDatabase());        DaoSession daoSession = daoMaster.newSession();        CarsDao carsDao = daoSession.getCarsDao();        QueryBuilder<Cars> qb = carsDao.queryBuilder();        List<Cars> list = qb.list();        return list;    }    /**     * 获取可读数据库     */    public SQLiteDatabase getReadableDatabase()    {        if (openHelper == null)        {            openHelper = new DaoMaster.DevOpenHelper(mContext, "dao_db", null);        }        SQLiteDatabase db = openHelper.getReadableDatabase();        return db;    }    /**     * 获取可写数据库     */    public SQLiteDatabase getWritableDatabase()    {        if (openHelper == null)        {            openHelper = new DaoMaster.DevOpenHelper(mContext, "dao_db", null);        }        SQLiteDatabase db = openHelper.getWritableDatabase();        return db;    }}

*相关的测试类：*

import android.app.Activity;import android.os.Bundle;import android.view.View;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends Activity{    private ListView listView;    DBManager dbManager;    private List<Cars> cars = new ArrayList<>();    private MyAdapter myAdapter;    private com.qihancloud.greendaotest.DaoMaster.DevOpenHelper openHelper;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        listView = (ListView) findViewById(R.id.list);        dbManager = new DBManager(MainActivity.this);    }    public void insert(View view)    {        cars.clear();        for (int i = 0; i < 10; i++)        {            Cars user = new Cars();            user.setId(i);            user.setCar_name("飞车：" + i);            user.setCar_price("100000" + i);            user.setCar_factory("第" + i + "厂");            cars.add(user);        }        DBManager.getInstance(MainActivity.this).insertUserList(cars);    }    public void update(View view)    {        DBManager.getInstance(MainActivity.this).update();    }    public void delete(View view)    {        DBManager.getInstance(MainActivity.this).delete();    }    public void query(View view)    {        cars = DBManager.getInstance(MainActivity.this).query();        myAdapter = new MyAdapter(MainActivity.this, cars);        listView.setAdapter(myAdapter);    }}

相关的布局文件就不贴代码了，喜欢的朋友欢迎交流学习。