1.添加依赖：

implementation 'android.arch.persistence.room:runtime:1.0.0'
annotationProcessor 'android.arch.persistence.room:compiler:1.0.0'

2.创建Entity实体类：

每个Entity实体对象都会映射为表中的某一行

@Entity(tableName = "student")						//使用Entity注解定义表名为student
public class Student{
 
 	 @PrimaryKey(autoGenerate = true)				//设置主键，并且定义自增增
 	 @ColumnInfo(name = "uid")						
 	 private int uid;

 	 @ColumnInfo(name = "name")						//这里变量名和字段名不同，注解不可省略
 	 private String studentName;
 	
 	 private String age;							//变量名和字段名都是age，可以省略不写
 	
 	 public User() {								//必须指定一个构造方法，room框架需要。并且只能指定一个
 	 }
 	
	 @Ignore										//其他构造方法要添加@Ignore注解
 	 public User(int uid) {
    	 this.uid = uid;
 	 }
	
 	 public int getUid() {							//三个字段的Setter、Getter方法必须添加，这里省略
    	 return uid;
 	 }

	 public void setUid(int uid) {
	     this.uid = uid;
	 }
	 ...
}

3.创建Dao接口：

@Dao
public interface StudentDao {
    @Query("SELECT * FROM user")
    List<Student> getAllStudent();

    @Insert
    void insert(Student... users);

    @Update
    void update(Student... users);

    @Delete
    void delete(Student... users);
}

Insert, Update, Delete可以传入多种不同的参数。例如：

@Insert
void insert(Student... students);

@Insert
void insert(Student student);

@Insert
void insert(List<Student> studentLists);

Query也可以返回多种不同的类型。

@Query("SELECT * FROM student")
List<Student> getAllStudent();

@Query("SELECT * FROM student WHERE id=:id")
User getStudent(int id);

@Query("SELECT * FROM student")
Cursor getStudentCursor();

@Query("SELECT * FROM user WHERE age=:age")
List<User> getStudentByAge(int age);

4.创建数据库：

@Database(entities = { Student.class }, version = 1,exportSchema = false)
public abstract class StudentDatabase extends RoomDatabase {

    private static final String DB_NAME = "StudentDatabase.db";
    private static volatile StudentDatabase instance;

    static synchronized StudentDatabase getInstance(Context context) {
        if (instance == null) {
            instance = create(context);
        }
        return instance;
    }

    private static StudentDatabase create(final Context context) {
        return Room.databaseBuilder(
            context,
            StudentDatabase.class,
            DB_NAME).build();
    }

    public abstract UserDao getUserDao();
}

5.使用数据库：

必须在后台线程中使用数据库，否则会报错

Student student = new Student();
student.setName("Tom");
student.setAge(18);
UserDatabase
        .getInstance(context)
        .getUserDao()
        .insert(student);
        
List<User> allUsers = UserDatabase
        .getInstance(context)
        .getUserDao()
        .getAllStudents();

6.数据库迁移：

1.在Student实体类中新增一个字段：

private int grade;

2.在Student实体类中新增一个字段：

@Database(entities = { Student.class }, version = 2, exportSchema = false)
public abstract class StudentDatabase extends RoomDatabase {
	//...
    public abstract UserDao getUserDao();
}

3.创建一个Migration对象，在数据库中新增grade列

static final Migration MIGRATION_1_2 = new Migration(1, 2) {
    @Override
    public void migrate(SupportSQLiteDatabase database) {
        database.execSQL("ALTER TABLE department ADD COLUMN grade INTEGER");
    }
};

4.在数据库对象创建时候添加该Migration对象

 AppDatabase db = Room.databaseBuilder(getApplicationContext(),
            AppDatabase.class, "roomDemo-database")
            .addMigrations(AppDatabase.MIGRATION_1_2)
            .build();