Упражнение 4. Работа с дати

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.CalendarView
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast
import androidx.core.view.isVisible
import java.text.DateFormat
import java.text.SimpleDateFormat
import java.time.LocalDate
import java.time.chrono.ChronoLocalDate
import java.time.chrono.ChronoPeriod
import java.time.format.DateTimeFormatter
import java.time.temporal.ChronoUnit
import java.util.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val cv=findViewById<CalendarView>(R.id.calendarView)
        cv.isVisible=false
        cv.setOnDateChangeListener { calendarView, year, month, day ->
            val tv=findViewById<TextView>(R.id.textView)

            //tv.text= String.format("%d.%02d.%dг.",day,month+1,year)
            //tv.text= String.format("%d.%02d.%dг.",day,month+1,year%100)
            // Изчисляване на разлика в дати
            //val d1=LocalDate.now()
            //val d2=LocalDate.of(year,month+1,day)
            //tv.text=ChronoPeriod.between(d1,d2).toString()
            //tv.text=ChronoUnit.DAYS.between(d1,d2).toString()+" дни"
            // Активният контрол
            val curr=this.currentFocus
            // Ако контролът е EditText
            if( curr is EditText) {
                val izbor=String.format("%d.%02d.%d",day,month+1,year)
                // На активният контрол му задаваме стойност
                (curr as EditText).setText(izbor)
                cv.isVisible=false
            }
        }
        findViewById<EditText>(R.id.editTextDate).setOnFocusChangeListener { view, b ->
            cv.isVisible=true
        }
        findViewById<EditText>(R.id.editTextDate2).setOnFocusChangeListener { view, b ->
            cv.isVisible=true
        }
    }

    fun btn_dnes(view:View){
        val tv=findViewById<TextView>(R.id.textView)
        val dnes=LocalDate.now()
        //tv.text=dnes.toString()

        // Ден.име на месец.година
        //tv.text=dnes.dayOfMonth.toString()+"."+dnes.month+"."+dnes.year

        // ден.месец.година
        //tv.text=String.format("%2d.%02d.%4d",dnes.dayOfMonth,dnes.monthValue,dnes.year)

        //val frm=SimpleDateFormat("d/MM/yyyy")
        //val dnes2= Calendar.getInstance()
        //tv.text=frm.format(dnes2.time)

        //val frm=DateTimeFormatter.ofPattern("d.MM.yyyy")
        //tv.text=frm.format(dnes)

        val imena= listOf("Яну","Фев","Мар","Апр","Май","Юни","Юли","Авг","Сеп","Окт","Ное","Дек")
        //tv.text=dnes.dayOfMonth.toString()+"."+ imena[dnes.monthValue]+"."+dnes.year
        tv.text= String.format("%d.%s.%d",dnes.dayOfMonth,imena[dnes.monthValue-1],dnes.year)
    }

    fun btn_razlika(view: View) {
        val ed1=findViewById<EditText>(R.id.editTextDate)
        val ed2=findViewById<EditText>(R.id.editTextDate2)
        if( ed1.text.isEmpty() || ed2.text.isEmpty() )
            Toast.makeText(this, "Има невъведена дата", Toast.LENGTH_SHORT).show()
        else {
            val maska=DateTimeFormatter.ofPattern("d.MM.yyyy")
            val date1=LocalDate.parse(ed1.text,maska)
            val date2=LocalDate.parse(ed2.text,maska)
            val tv=findViewById<TextView>(R.id.textView)
            tv.text=ChronoUnit.DAYS.between(date1,date2).toString()
        }
    }

    fun btn_zad(view: View) {
        val tv=findViewById<TextView>(R.id.textView)
        val dnes=LocalDate.now()
        val kam=LocalDate.of(2022,4,18)
        tv.text="до "+kam.toString()+" остават "+
                ChronoUnit.DAYS.between(dnes,kam).toString()+" дни"
    }
}

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="20dp"
    android:layout_marginTop="40dp"
    android:text="Hello World!"
    app:layout_constraintStart_toEndOf="@+id/button"
    app:layout_constraintTop_toBottomOf="@+id/button2" />

<EditText
    android:id="@+id/editTextDate"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="56dp"
    android:layout_marginTop="16dp"
    android:ems="10"
    android:inputType="date"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<EditText
    android:id="@+id/editTextDate2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="date"
    app:layout_constraintStart_toStartOf="@+id/editTextDate"
    app:layout_constraintTop_toBottomOf="@+id/editTextDate" />

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:onClick="btn_zad"
    android:text="Dnes"
    app:layout_constraintStart_toStartOf="@+id/editTextDate2"
    app:layout_constraintTop_toBottomOf="@+id/editTextDate2" />

<Button
    android:id="@+id/button2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="61dp"
    android:layout_marginTop="17dp"
    android:onClick="btn_razlika"
    android:text="Razlika"
    app:layout_constraintStart_toEndOf="@+id/button"
    app:layout_constraintTop_toBottomOf="@+id/editTextDate2" />

<CalendarView
    android:id="@+id/calendarView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="30dp"
    android:layout_marginBottom="25dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent" />