使用静态编程语言在Android房间中将日期字符串迁移到Int

Question

我需要在Android 9.0上使用静态编程语言1.4.32中的Room 2.3迁移我的数据库。在我的初始数据库中，我的日期是一个字符串（即“2021-06-03T22:54:15.406-07:00[America/Los_Angeles]”），我想在迁移期间将其迁移到和Int（即toEpochII）。看来我应该能够使用SupportSQLiteDatabase.query中的游标来遍历我的数据并进行转换，但是当我进行查询时，我的游标计数为-1。

这是我的迁移：

val Migration_7_8 = object : Migration(7, 8) {
    override fun migrate(database: SupportSQLiteDatabase)
    {
        database.execSQL("ALTER TABLE logEntryTable ADD COLUMN dateTime INTEGER NOT NULL DEFAULT 0" )

        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryId TO id")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryAction TO 'action'")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryTime TO time")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryLatitude TO latitude")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryLongitude TO longitude")

        val cursor = database.query(SimpleSQLiteQuery("SELECT * FROM logEntryTable"))
        val idColumnIndex = cursor.getColumnIndex("id")
        val timeColumnIndex = cursor.getColumnIndex("time")

        while(!cursor.isAfterLast)
        {
            val timeStr = cursor.getString(3)
            val id = cursor.getInt(idColumnIndex)

            val time: ZonedDateTime = ZonedDateTime.parse(timeStr)

            val contentValues = ContentValues()
            contentValues.put("time", time.toEpochSecond())
            database.update("logEntryTable", SQLiteDatabase.CONFLICT_NONE, contentValues, "id=:id", arrayOf(id))

            cursor.moveToNext()
        }
    }
}

Answer 1

所以，当光标最初指向无位置（-1）时，您需要在使用它之前将其移动到某个有效位置

要将其移动到第一个位置，可以在while循环之前调用moveToNext（）

Answer 2

结果证明（Zain在评论中也提到）唯一的问题是我必须调用游标。moveToNext（）显然是为了在while循环中使用光标之前初始化光标（即移动到第一行）：

val Migration_7_8 = object : Migration(7, 8) {
    override fun migrate(database: SupportSQLiteDatabase)
    {
        database.execSQL("ALTER TABLE logEntryTable ADD COLUMN dateTime INTEGER NOT NULL DEFAULT 0" )

        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryId TO id")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryAction TO 'action'")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryTime TO time")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryLatitude TO latitude")
        database.execSQL("ALTER TABLE logEntryTable RENAME COLUMN logEntryLongitude TO longitude")

        val cursor = database.query(SimpleSQLiteQuery("SELECT * FROM logEntryTable"))
        val idColumnIndex = cursor.getColumnIndex("id")
        val timeColumnIndex = cursor.getColumnIndex("time")



        cursor.moveToNext()  // <======================  HERE



        while(!cursor.isAfterLast)
        {
            val timeStr = cursor.getString(3)
            val id = cursor.getInt(idColumnIndex)

            val time: ZonedDateTime = ZonedDateTime.parse(timeStr)

            val contentValues = ContentValues()
            contentValues.put("time", time.toEpochSecond())
            database.update("logEntryTable", SQLiteDatabase.CONFLICT_NONE, contentValues, "id=:id", arrayOf(id))

            cursor.moveToNext()
        }
    }
}