Android房间按月或按年汇总数据

Question

我试图绘制我使用Room存储的数据。为此，我有一个会话实体，然后是会话的1到多个关系，例如会话期间记录的步数，血压和氧气水平。

对于会话我存储开始时间，我希望能够按此日期对会话进行分组（进入日/月/年箱）。然后，对于每个时间间隔，我需要获得图表上显示的步数，血压和氧气水平的平均值。例如，多个会话可能会在4/23/2018发生，但我想获得当天的平均值。

会话

@Entity
public class Session implements Serializable {
    public final static String TABLE = "Session";

    @PrimaryKey(autoGenerate = true)
    private long sid;

    @ColumnInfo(name = "startTimestamp")
    private Date startTimestamp;

    @ColumnInfo(name = "endTimestamp")
    private Date endTimestamp;

    public long getSid() { return sid; }
    public Date getStartTimestamp() { return startTimestamp; }
    public Date getEndTimestamp() { return endTimestamp; }
    public long getDuration() { return endTimestamp.getTime() - startTimestamp.getTime(); }

    public void setSid(long sid) { this.sid = sid; }
    public void setStartTimestamp(Date timestamp) { this.startTimestamp = timestamp; }
    public void setEndTimestamp(Date timestamp) { this.endTimestamp = timestamp; }

    @android.arch.persistence.room.Dao
    public interface SessionDao {

        @Query("SELECT * FROM " + TABLE)
        List<Session> getAll();

        @Query("SELECT * FROM " + TABLE)
        List<SessionWithRelations> getAllWithRelations();

        @Query("SELECT * FROM " + TABLE + " ORDER BY :orderBy")
        List<SessionWithRelations> getAllWithRelations(String orderBy);

        @Insert
        long insert(Session session);

        @Update
        void update(Session session);

        @Delete
        void delete(Session session);
    }
}

SessionOxygen

@Entity
public class SessionOxygen implements Serializable {
    public final static String TABLE = "SessionOxygen";

    @PrimaryKey(autoGenerate = true)
    private long id;

    @ColumnInfo(name = "sid")
    private long sid;

    @ColumnInfo(name = "timestamp")
    private Date timestamp;

    @ColumnInfo(name = "oxygen")
    private int oxygen;

    public long getId() { return id; }
    public long getSid() { return sid; }
    public Date getTimestamp() { return timestamp; }
    public int getOxygen() { return oxygen; }

    public void setId(long id) { this.id = id; }
    public void setSid(long sid) { this.sid = sid; }
    public void setTimestamp(Date timestamp) { this.timestamp = timestamp; }
    public void setOxygen(int oxygen) { this.oxygen = oxygen; }

    @android.arch.persistence.room.Dao
    public interface OxygenDao {

        @Query("SELECT * FROM " + TABLE + " WHERE sid=:sid")
        List<SessionOxygen> getAllForSession(int sid);

        @Insert
        long[] insertAll(List<SessionOxygen> oxygens);

        @Insert
        long insert(SessionOxygen oxygen);
    }

}

会话POJO

public class SessionWithRelations {
    @Embedded
    public Session session;

    @Relation(parentColumn = "sid", entityColumn = "sid", entity = SessionBloodPressure.class)
    public List<SessionBloodPressure> bloodPressureList = new ArrayList<>();

    @Relation(parentColumn = "sid", entityColumn = "sid", entity = SessionWeight.class)
    public List<SessionWeight> weightList = new ArrayList<>();

    @Relation(parentColumn = "sid", entityColumn = "sid", entity = SessionOxygen.class)
    public List<SessionOxygen> oxygenList = new ArrayList<>();

    public int averageOxygen() {
        int sum = 0;
        if (oxygenList.size() > 0) {
            for (SessionOxygen oxygen : oxygenList) {
                sum += oxygen.getOxygen();
            }
            return sum / oxygenList.size();
        }
        return 0;
    }

    public int averageWeight() {
        int sum = 0;
        if (oxygenList.size() > 0) {
            for (SessionWeight weight : weightList) {
                sum += weight.getWeight();
            }
            return sum / weightList.size();
        }
        return 0;
    }

    public int averageDiastolic() {
        int sum = 0;
        if (oxygenList.size() > 0) {
            for (SessionBloodPressure bloodPressure : bloodPressureList) {
                sum += bloodPressure.getDiastolic();
            }
            return sum / weightList.size();
        }
        return 0;
    }

    public int averageSystolic() {
        int sum = 0;
        if (oxygenList.size() > 0) {
            for (SessionBloodPressure bloodPressure : bloodPressureList) {
                sum += bloodPressure.getSystolic();
            }
            return sum / weightList.size();
        }
        return 0;
    }
}

我刚将整个应用程序切换到使用Room，但我觉得使用原始查询会非常容易。我不确定这对房间是否可行。我查看了RawQuery文档但看起来只允许在运行时生成查询，但仍然只返回实体，我需要返回自定义列。

// Group by month and get average Oxygen level for each month with data
select s.startTimestamp, AVG(o.oxygen) as oxygenAverage
    from Session s
    left join SessionOxygen o on s.sid = o.sid
    group by DATE_FORMAT(s.startTimestamp, "%m-%Y");

我有一种感觉，我必须对POJO课做一些事情，但我不知道如何去做。

我认为我的另一个选择是在代码中聚合它，但这将非常低效和混乱。