How to add date separators in recycler view using Paging Library?

Question

After a lot of searching, I know its possible with regular adapter, but I have no idea how to do it using Paging Library. I don`t need code just a clue.

Example

Answer 1

You can achieve the same result using insertSeparators in Paging 3 library. Make sure your items are sorted by date.

Inside or viewmodel retrieve a Pager something like that

private val communicationResult: Flow> = Pager(
    PagingConfig(
        pageSize = 50,
        enablePlaceholders = false,
        maxSize = 400,
        initialLoadSize = 50
    )
) {
    CommunicationPagingSource(repository)
}.flow.cachedIn(viewModelScope)

After all insert separators like a header

val groupedCommunicationResult = communicationResult
        .map { pagingData -> pagingData.map { CommunicationHistoryModel.Body(it) } }
        .map {
            it.insertSeparators{ after, before ->
                if (before == null) {
                    //the end of the list
                    return@insertSeparators null
                }

                val afterDateStr = after?.createdDate
                val beforeDateStr = before.createdDate

                if (afterDateStr == null || beforeDateStr == null)
                    return@insertSeparators null

                val afterDate = DateUtil.parseAsCalendar(afterDateStr)?.cleanTime()?.time ?: 0
                val beforeDate = DateUtil.parseAsCalendar(beforeDateStr)?.cleanTime()?.time ?: 0

                if (afterDate > beforeDate) {
                    CommunicationHistoryModel.Header( DateUtil.format(Date(beforeDate))) // dd.MM.yyyy
                } else {
                    // no separator
                    null
                }
            }
        }

cleanTime is required for grouping by dd.MM.yyyy ignoring time

fun Calendar.cleanTime(): Date {
    set(Calendar.HOUR_OF_DAY, 0)
    set(Calendar.MINUTE, 0)
    set(Calendar.SECOND, 0)
    set(Calendar.MILLISECOND, 0)
    return this.time
}