gradle依赖：

// add for room
implementation "android.arch.persistence.room:runtime:1.1.1"
// room 配合 RxJava
implementation "android.arch.persistence.room:rxjava2:1.1.1"
annotationProcessor 'android.arch.persistence.room:compiler:1.1.1'// RxJava
implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
implementation 'io.reactivex.rxjava2:rxjava:2.1.3'

model对象：

import android.arch.persistence.room.Entity;
import android.arch.persistence.room.PrimaryKey;@Entity
public class User {// 用 @ColumnInfo 来标明数据库表的列名， 用 @PrimaryKey 来标示 主键@PrimaryKey(autoGenerate = true)private long    uid;private String  name;private String  address;private String  phone;private Integer age;public long getUid() {return uid;}public void setUid(long uid) {this.uid = uid;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}@Overridepublic String toString() {return "User{" + "uid=" + uid + ", name='" + name + '\'' + ", address='" + address + '\'' + ", phone='" + phone + '\'' + ", age=" +age + '}';}
}

相对应的DAO类：

1. Room也可以返回RxJava2中Publisher和Flowable:

import android.arch.persistence.room.Dao;
import android.arch.persistence.room.Insert;
import android.arch.persistence.room.OnConflictStrategy;
import android.arch.persistence.room.Query;
import java.util.List;import io.reactivex.Flowable;@Dao
public interface UserDao {@Insert(onConflict = OnConflictStrategy.REPLACE)List<Long> insert(User... users);@Query("SELECT * from user")Flowable<List<User>> loadUser();@Deletevoid delete(User user);
}

当准备好所有的 Model 和 DAO 后，我们就需要把它放入 DataBase 的管理中:

package com.soyoungboy.room.database;import android.arch.persistence.room.Database;
import android.arch.persistence.room.RoomDatabase;
import android.arch.persistence.room.TypeConverters;import com.soyoungboy.room.database.daos.BookDao;
import com.soyoungboy.room.database.daos.UserDao;
import com.soyoungboy.room.database.entities.Book;
import com.soyoungboy.room.database.entities.User;@Database(entities = {User.class, Book.class}, version = 3)
@TypeConverters({Converters.class})
public abstract class AppDatabase extends RoomDatabase {public abstract UserDao userDao();public abstract BookDao bookDao();}

Converters.java为时间转换的类：

1. 如果想要在数据库中存储Date，可以存储等价的Unix时间戳

public class Converters {@TypeConverterpublic static Date fromTimestamp(Long value) {return value == null ? null : new Date(value);}@TypeConverterpublic static Long dateToTimestamp(Date date) {return date == null ? null : date.getTime();}
}

Room数据库数据库升级：

1. Room使用Migration来实现数据库的迁移。每个Migration都指定了startVersion和endVersion。

import android.app.Application;
import android.arch.persistence.db.SupportSQLiteDatabase;
import android.arch.persistence.room.Room;
import android.arch.persistence.room.migration.Migration;public class AppApplication extends Application {private AppDatabase mAppDatabase;@Overridepublic void onCreate() {super.onCreate();mAppDatabase = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "android_room_dev.db").allowMainThreadQueries().addMigrations(MIGRATION_1_2, MIGRATION_2_3).build();}public AppDatabase getAppDatabase() {return mAppDatabase;}/*** 数据库版本 1->2 user表格新增了age列*/static final Migration MIGRATION_1_2 = new Migration(1, 2) {@Overridepublic void migrate(SupportSQLiteDatabase database) {database.execSQL("ALTER TABLE User ADD COLUMN age integer");}};/*** 数据库版本 2->3 新增book表格*/static final Migration MIGRATION_2_3 = new Migration(2, 3) {@Overridepublic void migrate(SupportSQLiteDatabase database) {database.execSQL("CREATE TABLE IF NOT EXISTS `book` (`uid` INTEGER PRIMARY KEY autoincrement, `name` TEXT , `userId` INTEGER, 'time' INTEGER)");}};
}

操作数据库：

1,首先获取AppDatabase对象：

AppDatabase mAppDatabase = ((AppApplication)getApplication()).getAppDatabase();

2,新增操作：

                User user = new User();user.setPhone("18320770932");user.setAddress("深圳");user.setName("soyoungboy");//              user.setAge("28");List<Long> ids = mAppDatabase.userDao().insert(user);

3,查询操作：

                mAppDatabase.userDao().loadUser().subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<List<User>>() {@Overridepublic void accept(List<User> entities) {if (entities != null) {for (User user : entities) {Log.d("soyoungboy", user.toString());}}}});

4,删除操作：

 findViewById(R.id.button_delete_user).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {User user = new User();user.setPhone("18320770932");user.setAddress("深圳");user.setName("soyoungboy");user.setUid(5);UserDao userDao = mAppDatabase.userDao();userDao.delete(user);}});