GreenDao基本使用_

最新推荐文章于 2024-12-07 19:18:50 发布

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本文介绍了一个基于GreenDAO的Android应用数据操作实例，包括数据的增删改查等基本操作。通过具体的代码实现展示了如何使用GreenDAO进行数据库交互。

Ben类：

@Entity
public class User {

    @Id
    private long id;
    @Property
    private String name;
    @Property
    private int age;

MyUserDao：

public class MyUserDao {

    Context context;

    public MyUserDao(Context context) {
        this.context = context;
    }

    /**
     * 插入一条数据
     */
    public void insertUser(User user) {
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getWritableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        userDao.insert(user);
    }

    /**
     * 插入用户集合
     *
     * @param users
     */
    public void insertUserList(List<User> users) {
        if (users == null || users.isEmpty()) {
            return;
        }
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getWritableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        userDao.insertInTx(users);
    }

    /**
     * 查询用户列表
     */
    public List<User> queryUserList() {
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getReadableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        QueryBuilder<User> qb = userDao.queryBuilder();
        List<User> list = qb.list();
        return list;
    }

    /**
     * 查询用户列表
     */
    public List<User> queryUserList(int age) {
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getReadableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        QueryBuilder<User> qb = userDao.queryBuilder();
        qb.where(UserDao.Properties.Age.gt(age)).orderAsc(UserDao.Properties.Age);
        List<User> list = qb.list();
        return list;
    }

    /**
     * 更新一条记录
     *
     * @param user
     */
    public void updateUser(User user) {
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getWritableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        userDao.update(user);
    }

    /**
     * 删除一条记录
     *
     * @param user
     */
    public void deleteUser(User user) {
        DaoMaster daoMaster = new DaoMaster(DBManager.getInstance(context).getWritableDatabase());
        DaoSession daoSession = daoMaster.newSession();
        UserDao userDao = daoSession.getUserDao();
        userDao.delete(user);
    }

}

DBManager：

public class DBManager {

    private final static String dbName = "test_db";
    private static DBManager mInstance;
    private DaoMaster.DevOpenHelper openHelper;
    private Context context;

    private DBManager(Context context) {
        this.context = context;
        openHelper = new DaoMaster.DevOpenHelper(context, dbName, null);
    }

    /**
     * 获取单例引用
     *
     * @param context
     * @return
     */
    public static DBManager getInstance(Context context) {
        if (mInstance == null) {
            synchronized (DBManager.class) {
                if (mInstance == null) {
                    mInstance = new DBManager(context);
                }
            }
        }
        return mInstance;
    }

    public SQLiteDatabase getReadableDatabase() {
        if (openHelper == null) {
            openHelper = new DaoMaster.DevOpenHelper(context, dbName, null);
        }
        SQLiteDatabase db = openHelper.getReadableDatabase();
        return db;
    }

    public SQLiteDatabase getWritableDatabase() {
        if (openHelper == null) {
            openHelper = new DaoMaster.DevOpenHelper(context, dbName, null);
        }
        SQLiteDatabase db = openHelper.getWritableDatabase();
        return db;
    }
}

MainActivity：

public class MainActivity extends AppCompatActivity {

    private MyUserDao dao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dao = new MyUserDao(this);

        for (int i = 20; i < 25; i++) {
            User user = new User();
            user.setId(Long.valueOf(i));
            user.setAge(i * 3);
            user.setName("第" + i + "人");
            dao.insertUser(user);
        }
        List<User> userList = dao.queryUserList();
        for (User user : userList) {
            Log.e("TAG", "queryUserList--before-->" + user.getId() + "--" + user.getName() +"--"+user.getAge());
            if (user.getId() == 10) {
                dao.deleteUser(user);
            }
            if (user.getId() == 13) {
                user.setAge(25);
                dao.updateUser(user);
            }
        }
        userList = dao.queryUserList();
        for (User user : userList) {
            Log.e("TAG", "queryUserList--after--->" + user.getId() + "---" + user.getName()+"--"+user.getAge());
        }

    }
}