Android Kotlin Room 查询 select 过去 7 天的记录

Question

我正在编写一份报告，该报告将从 Room 数据库中获取过去 7 天的数据。这是我简化的应用程序结构。

Entity Class:
@Entity(tableName = "cleaning")
data class Cleaning(
    @PrimaryKey(autoGenerate = true)
    val id: Long,
    val task: String,
    val timestamp: Date
)

类型转换器： class 日期类型转换器 {

@TypeConverter
fun fromTimeStampToDate(timestamp: Long?): Date? {
    return timestamp?.let {
        Date(it)
    }
}

@TypeConverter
fun fromDateToTimeStamp(date: Date?): Long? {
    return date?.time?.toLong()
}

数据访问对象Class提取：

@Query("SELECT * from cleaning WHERE (timestamp=Calendar.getInstance().time - 7) ORDER BY id DESC")
fun readSevenDaysData(): LiveData<List<CleaningRecord>>

问题是 (timestamp=Calendar.getInstance().time - 7)。当我使用 Calendar.getInstance().time

存储日期时，我不知道如何给出过去 7 天提取数据的范围

非常感谢任何正确方向的指导。

Answer 1

我相信下面会做你想要的:-

@Query("SELECT * from cleaning WHERE CAST((timestamp / 1000) AS INTEGER) BETWEEN strftime('%s','now','-7 days') AND strftime('%s','now')  ORDER BY id DESC;")

即 时间戳 存储到毫秒，因此除以 1000 会将值减少到秒。

strftime('%s' .... returns 秒数
'now' returns 当前日期时间
'-7 days' 相应地修改值
- 有关更全面的信息，请参阅 https://sqlite.org/lang_datefunc.html。
BETWEEN 等同于 >= AND <=
- 见https://sqlite.org/lang_expr.html#the_between_operator
CAST 是为了确保对等（整数值）进行比较。
- 见https://sqlite.org/lang_expr.html#cast_expressions

SQLite 不理解表达式 (timestamp=Calendar.getInstance().time - 7) 的含义，即使它理解它也只会得到与小于 7 天的时间完全匹配的数据，精确到毫秒。

已使用您的代码加上或被以下内容覆盖进行了测试：-

@Dao
interface Extract {

    @Insert
    fun insert(cleaning: Cleaning)

    @Query("SELECT * from cleaning WHERE CAST((timestamp / 1000) AS INTEGER) BETWEEN strftime('%s','now','-7 days') AND strftime('%s','now')  ORDER BY id DESC;")
    fun readSevenDaysData(): List<Cleaning>
}

显然 SQL 已更改，
此外，为了简洁和方便，没有使用 LiveData，

由于未提供 CleaningRecord 对象，因此仅返回了 Cleaning 对象。

@Database(entities = [Cleaning::class], version = 1, exportSchema = false) @TypeConverters( 值 = [DateTypeConverter::class]) 摘要 class TheDatabase: RoomDatabase() { 抽象乐趣 getExtractDao(): Extract

  companion object {
      private var instance: TheDatabase? = null
      fun getInstance(context: Context): TheDatabase {
          if (instance == null) {
              instance = Room.databaseBuilder(context,TheDatabase::class.java,"the_database.db")
                  .allowMainThreadQueries()
                  .build()
          }
          return instance as TheDatabase
      }
  }

}

带注释的@Database class，以及 getInstance 函数，再次指出，为简洁起见，使用了 allowMainThreadQueries。

最后 Activity 添加一些数据并使用相应的查询提取数据：-

class MainActivity : AppCompatActivity() {
    lateinit var db: TheDatabase
    lateinit var dao: Extract
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        db = TheDatabase.getInstance(this)
        dao = db.getExtractDao()

        dao.insert(Cleaning(100,"TASK001",Calendar.getInstance().time))
        dao.insert(Cleaning(200,"TASK002",Calendar.getInstance().time))

        for (c: Cleaning in dao.readSevenDaysData()) {
            Log.d("DBINFO","Cleaning Task = ${c.task} ID = ${c.id} ${c.timestamp.time}")
        }
    }
}

导致 :-

D/DBINFO: Cleaning Task = TASK002 ID = 200 1647400757156
D/DBINFO: Cleaning Task = TASK001 ID = 100 1647400757125

AppInspection 显示：-

另外使用App Inspection查询

SELECT *, timestamp /1000 AS timetosecond,  strftime('%s','now','-7 days') AS fromtime,  strftime('%s','now') AS totime   from cleaning WHERE CAST((timestamp / 1000) AS INTEGER) BETWEEN strftime('%s','now','-7 days') AND strftime('%s','now')  ORDER BY id DESC

运行进一步展示了 a) App Inspection 的用途以及 b) 查询的各个部分对实际数据的作用。

即以上导致：-

Android Kotlin Room 查询 select 过去 7 天的记录

Android Kotlin Room query to select record from last seven days

sqlite

kotlin

android-room