HomeFragment.kt

package hu.crm.myapplication.ui.home

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.lifecycle.ViewModelProvider
import androidx.recyclerview.widget.GridLayoutManager
import hu.crm.myapplication.CalendarItemModel
import hu.crm.myapplication.databinding.FragmentHomeBinding
import java.util.*

class HomeFragment : Fragment() {

    private lateinit var homeViewModel: HomeViewModel
    private val adapter = CalenderAdapter { dateClick(it) }
    private var actualNumberOfMonth = Calendar.getInstance().get(Calendar.MONTH) + 1
    private var actualYear = Calendar.getInstance().get(Calendar.YEAR)
    private lateinit var binding: FragmentHomeBinding

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        binding = FragmentHomeBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        homeViewModel = ViewModelProvider(this).get(HomeViewModel::class.java)

        binding.fragmentCalendarRecyclerView.layoutManager = GridLayoutManager(context, 7)
        binding.fragmentCalendarRecyclerView.adapter = adapter

        binding.fragmentCalendarNextButton.setOnClickListener {
            actualNumberOfMonth++
            handleButtons()
        }

        binding.fragmentCalendarBackButton.setOnClickListener {
            actualNumberOfMonth--
            handleButtons()
        }

        handleButtons()
    }

    private fun dateClick(calendar: Calendar) {
        //view?.showSnackBar("Kattintás a ${calendar.time} elemre")
    }

    private fun handleButtons() {
        if (actualNumberOfMonth < 1) {
            actualNumberOfMonth = 12
            actualYear--
        }

        if (actualNumberOfMonth > 12) {
            actualNumberOfMonth = 1
            actualYear++
        }

        binding.numberOfMonth = actualNumberOfMonth
        binding.year = actualYear
        adapter.submitList(createMonthDateList())
    }

    private fun createMonthDateList(): List<CalendarItemModel> {
        val models: MutableList<CalendarItemModel> = mutableListOf()

        val calendar = Calendar.getInstance()
        calendar.set(Calendar.HOUR, 0)
        calendar.set(Calendar.MINUTE, 0)
        calendar.set(Calendar.MILLISECOND, 0)
        calendar.set(Calendar.SECOND, 0)

        calendar.set(Calendar.MONTH, actualNumberOfMonth - 1)
        calendar.set(Calendar.YEAR, actualYear)
        calendar.set(Calendar.DAY_OF_MONTH, 1)
        calendar.add(Calendar.DAY_OF_MONTH, 2 - calendar[Calendar.DAY_OF_WEEK])

        while (models.size < 35) {
            models.add(
                CalendarItemModel(
                    calendar.clone() as Calendar,
                    models.size,
                    models.size,
                    actualNumberOfMonth
                )
            )
            calendar.add(Calendar.DAY_OF_MONTH, 1)
        }

        return models
    }
}