GreenDao3.0框架使用详解

最近将一个使用蓝牙设备测人体温度的穿戴设备项目做完了,有时间来总结下本项目中使用到的一些基础知识。上次写过关于GreenDao3.0框架在使用前的配置问题,可点击查看GreenDao3.0框架使用时IDE的配置问题,下面将详细的讲解下具体的使用过程。

先了解下GreenDao这个框架:


greenDAO 是一款开源的面向 Android 的轻便、快捷的 ORM 框架,将 Java 对象映射到 SQLite 数据库中,我们操作数据库的时候,不在需要编写复杂的 SQL语句, 在性能方面,greenDAO 针对 Android 进行了高度优化, 最小的内存开销 、依赖体积小 同时还是支持数据库加密。

greenDAO 官网地址: http://greenrobot.org/greendao/

DaoMaster:

使用 greenDAO 的入口点。DaoMaster 负责管理数据库对象(SQLiteDatabase)和 DAO 类(对象),我们可以通过它内部类 OpenHelper 和 DevOpenHelper SQLiteOpenHelper 创建不同模式的 SQLite 数据库。

DaoSession :

管理指定模式下的所有 DAO 对象,DaoSession提供了一些通用的持久性方法比如插入、负载、更新、更新和删除实体。

XxxDAO :

每个实体类 greenDAO 多会生成一个与之对应DAO对象,如:User 实体,则会生成一个一个UserDao 类

Entities

可持久化对象。通常, 实体对象代表一个数据库行使用标准 Java 属性(如一个POJO 或 JavaBean )。

编译后在gen包下会多出三个类,分别是TempDataDao,DaoMaster,DaoSession.

(想插入图片,但是老是插入不成功,这CSDN也是醉了)

TempData实体类里面是这样的:

/**  * Created by jjg on 2017/3/23.  */  @Entity
    public class TempData {
        @Id
        private Long id;
        private float temp;
        private float touchData;
        private String time;
        @Generated(hash = 2018402591)
        public TempData(Long id, float temp, float touchData, String time) {
            this.id = id;
            this.temp = temp;
            this.touchData = touchData;
            this.time = time;
        }
        @Generated(hash = 1851873653)
        public TempData() {
        }
        public Long getId() {
            return this.id;
        }
        public void setId(Long id) {
            this.id = id;
        }
        public float getTemp() {
            return this.temp;
        }
        public void setTemp(float temp) {
            this.temp = temp;
        }
        public float getTouchData() {
            return this.touchData;
        }
        public void setTouchData(float touchData) {
            this.touchData = touchData;
        }
        public String getTime() {
            return this.time;
        }
        public void setTime(String time) {
            this.time = time;
        }
}

可见这个实体类中有四个属性,分别是id,温度值,接触值,和对应的时间。

我这边是蓝牙每隔8秒发送一个数据过来,APP在拿到数据的时候将数据存到数据库中去,具体怎么使用GreenDao存放数据呢?

首先,我们来分析下TempDataDao,DaoMaster,DaoSession是干嘛用的?

先看下DaoMaster类里面的代码:

package com.myself.zhw.gen;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.util.Log;

import org.greenrobot.greendao.AbstractDaoMaster;
import org.greenrobot.greendao.database.StandardDatabase;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.database.DatabaseOpenHelper;
import org.greenrobot.greendao.identityscope.IdentityScopeType;


// THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.
/**  * Master of DAO (schema version 2): knows all DAOs.  */ public class DaoMaster extends AbstractDaoMaster {
    public static final int SCHEMA_VERSION = 2;//框架版本号为2,也就是说我当前的GreenDao版本是3.2.0版本的

    /** Creates underlying database table using DAOs. */  /*创建所有的表格用到的方法,因为表格是建在数据库中的,所以提供了两个参数,
    第一个参数是数据库,第二个参数是这个表格是否存在,不存在才创建,存在的话就
    不用创建,这个方法中只有一句代码,调用了TmepDataDao类中的最原始的sqlite创建表格的
    方法去创建表格(最原始的创建数据库的语法这里就不讲了)*/
    public static void createAllTables(Database db, boolean ifNotExists) {
        TempDataDao.createTable(db, ifNotExists);
    }

    /** Drops underlying database table using DAOs. */  /*这个方法是删除所有数据表格用的,具体的删除方法也是使用最原始的sqlite数据库
    的增删改查语句实现的,这个方法也是在TempDataDao类中*/
    public static void dropAllTables(Database db, boolean ifExists) {
        TempDataDao.dropTable(db, ifExists);
    }

    /**  * WARNING: Drops all table on Upgrade! Use only during development.  * Convenience method using a {@link DevOpenHelper}.  */  public static DaoSession newDevSession(Context context, String name) {
        Database db = new DevOpenHelper(context, name).getWritableDb();
        DaoMaster daoMaster = new DaoMaster(db);
        return daoMaster.newSession();
    }

    public DaoMaster(SQLiteDatabase db) {//构造方法
        this(new StandardDatabase(db));
    }

    public DaoMaster(Database db) {//构造方法
        super(db, SCHEMA_VERSION);
        registerDaoClass(TempDataDao.class);
    }

    public DaoSession newSession() {//拿到DaoSession对象
        return new DaoSession(db, IdentityScopeType.Session, daoConfigMap);
    }

    public DaoSession newSession(IdentityScopeType type) {//拿到DaoSession对象
        return new DaoSession(db, type, daoConfigMap);
    }

    /**  * Calls {@link #createAllTables(Database, boolean)} in {@link #onCreate(Database)} -  */  public static abstract class OpenHelper extends DatabaseOpenHelper {
        public OpenHelper(Context context, String name) {
            super(context, name, SCHEMA_VERSION);
        }

        public OpenHelper(Context context, String name, CursorFactory factory) {
            super(context, name, factory, SCHEMA_VERSION);
        }

        @Override
        public void onCreate(Database db) {//表格的创建
            Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
            createAllTables(db, false);
        }
    }

    /** WARNING: Drops all table on Upgrade! Use only during development. */  /**  * DevOpenHelperDaoMaster的内部类,DevOpenHelper类继承OpenHelper类,而OperHelper类又是继承DatabaseOpenHelper  * 类,DatabaseOpenHelper类又继承SQLiteOpenHelper类,在使用最原始的SQL语句创建数据库的时候,就使用到了SQLiteOpenHelper  * 可见,这里也是一样的  */  public static class DevOpenHelper extends OpenHelper {
        public DevOpenHelper(Context context, String name) {
            super(context, name);
        }

        public DevOpenHelper(Context context, String name, CursorFactory factory) {
            super(context, name, factory);
        }

        @Override
        public void onUpgrade(Database db, int oldVersion, int newVersion) {//表格的更新,更新之前先删,再重新创建
            Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
            dropAllTables(db, true);
            onCreate(db);
        }
    }

}

从代码结构可以看出,DaoMaster的功能还是很强大的,是个对Dao进行管理和创建数据库的类。

再看下DaoSession类

package com.myself.zhw.gen;

import java.util.Map;

import org.greenrobot.greendao.AbstractDao;
import org.greenrobot.greendao.AbstractDaoSession;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.identityscope.IdentityScopeType;
import org.greenrobot.greendao.internal.DaoConfig;


// THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.

/**  * {@inheritDoc}  *  * @see org.greenrobot.greendao.AbstractDaoSession  */ public class DaoSession extends AbstractDaoSession {

    private final DaoConfig tempDataDaoConfig;

    private final TempDataDao tempDataDao;

    public DaoSession(Database db, IdentityScopeType type, Mapextends AbstractDao, ?>>, DaoConfig>
            daoConfigMap) {
        super(db);

        tempDataDaoConfig = daoConfigMap.get(TempDataDao.class).clone();
        tempDataDaoConfig.initIdentityScope(type);

        tempDataDao = new TempDataDao(tempDataDaoConfig, this);

        registerDao(TempData.class, tempDataDao);
    }
    
    public void clear() {
        tempDataDaoConfig.clearIdentityScope();
    }

    public TempDataDao getTempDataDao() {
        return tempDataDao;
    }

}
再看下TempDataDao类

package com.myself.zhw.gen;

import android.database.Cursor;
import android.database.sqlite.SQLiteStatement;

import org.greenrobot.greendao.AbstractDao;
import org.greenrobot.greendao.Property;
import org.greenrobot.greendao.internal.DaoConfig;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.database.DatabaseStatement;

// THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.
/**  * DAO for table "TEMP_DATA". */ public class TempDataDao extends AbstractDao, Long> {

    public static final String TABLENAME = "TEMP_DATA";

    /**  * Properties of entity TempData.
* Can be used for QueryBuilder and for referencing column names. */ public static class Properties { public final static Property Id = new Property(0, Long.class, "id", true, "_id"); public final static Property Temp = new Property(1, float.class, "temp", false, "TEMP"); public final static Property TouchData = new Property(2, float.class, "touchData", false, "TOUCH_DATA"); public final static Property Time = new Property(3, String.class, "time", false, "TIME"); } public TempDataDao(DaoConfig config) { super(config); } public TempDataDao(DaoConfig config, DaoSession daoSession) { super(config, daoSession); } /** Creates the underlying database table. */ public static void createTable(Database db, boolean ifNotExists) { String constraint = ifNotExists? "IF NOT EXISTS ": ""; db.execSQL("CREATE TABLE " + constraint + "\"TEMP_DATA\" (" + // "\"_id\" INTEGER PRIMARY KEY ," + // 0: id "\"TEMP\" REAL NOT NULL ," + // 1: temp "\"TOUCH_DATA\" REAL NOT NULL ," + // 2: touchData "\"TIME\" TEXT);"); // 3: time } /** Drops the underlying database table. */ public static void dropTable(Database db, boolean ifExists) { String sql = "DROP TABLE " + (ifExists ? "IF EXISTS " : "") + "\"TEMP_DATA\""; db.execSQL(sql); } @Override protected final void bindValues(DatabaseStatement stmt, TempData entity) { stmt.clearBindings(); Long id = entity.getId(); if (id != null) { stmt.bindLong(1, id); } stmt.bindDouble(2, entity.getTemp()); stmt.bindDouble(3, entity.getTouchData()); String time = entity.getTime(); if (time != null) { stmt.bindString(4, time); } } @Override protected final void bindValues(SQLiteStatement stmt, TempData entity) { stmt.clearBindings(); Long id = entity.getId(); if (id != null) { stmt.bindLong(1, id); } stmt.bindDouble(2, entity.getTemp()); stmt.bindDouble(3, entity.getTouchData()); String time = entity.getTime(); if (time != null) { stmt.bindString(4, time); } } @Override public Long readKey(Cursor cursor, int offset) { return cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0); } @Override public TempData readEntity(Cursor cursor, int offset) { TempData entity = new TempData( // cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0), // id cursor.getFloat(offset + 1), // temp cursor.getFloat(offset + 2), // touchData cursor.isNull(offset + 3) ? null : cursor.getString(offset + 3) // time ); return entity; } @Override public void readEntity(Cursor cursor, TempData entity, int offset) { entity.setId(cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0)); entity.setTemp(cursor.getFloat(offset + 1)); entity.setTouchData(cursor.getFloat(offset + 2)); entity.setTime(cursor.isNull(offset + 3) ? null : cursor.getString(offset + 3)); } @Override protected final Long updateKeyAfterInsert(TempData entity, long rowId) { entity.setId(rowId); return rowId; } @Override public Long getKey(TempData entity) { if(entity != null) { return entity.getId(); } else { return null; } } @Override public boolean hasKey(TempData entity) { return entity.getId() != null; } @Override protected final boolean isEntityUpdateable() { return true; } }
现在如何创建数据库?

创建数据库选择在application中完成

public class tempteratureApplication extends Application {
    private static Context mcontext;
    private static DaoSession mDaoSession;
    @Override
    public void onCreate() {
        super.onCreate();
        mcontext = getApplicationContext();
        createDataBase();
        GreenDaoManager.getInstance();
    }

//    public static DaoSession getmDaoSession(){
//        return mDaoSession;
//    }
    //DaoMaster的作用在这里体现了
    private void createDataBase(){
        DaoMaster.DevOpenHelper devOpenHelper=new DaoMaster.DevOpenHelper(tempteratureApplication.getContext(),"TEMP_DATA");
        Log.e("生成devOpenHelper",devOpenHelper+"");
        SQLiteDatabase db=devOpenHelper.getWritableDatabase();
        Log.e("生成数据库",db+"");
        DaoMaster daoMaster=new DaoMaster(db);
        mDaoSession=daoMaster.newSession();
    }

    public static Context getContext(){
        return mcontext;
    }
}

TempDataDao是继承AbstractDao的,在AbstractDao中有一个向数据库插入数据的方法insert()方法,所以要想插入数据,就要先创建TempDataDao对象,这也是TempDataDao的作用,还有删除,查询,修改等等的语句全部要用到TempDataDao,可在AbstractDao类中查询到。

后面还会继续给出Demo,用一个详细的例子来说明一切。

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