Упражнение 2. Работа със стрингове

package com.example.upr2_strings

import android.graphics.Color
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.text.TextUtils
import android.view.View
import android.widget.CheckBox
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast

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

    fun Proverka_Ime():Boolean
    {
        val ime=findViewById<EditText>(R.id.editTextTextPersonName).text.toString().uppercase()

        if( ime.isEmpty() ) {
            Toast.makeText(this, "Въведете имена", Toast.LENGTH_SHORT).show()
            return false
        }
        if( ime.matches("[A-Z -]+".toRegex())==false )
        {
            Toast.makeText(this, "Използвайте само букви", Toast.LENGTH_SHORT).show()
            return false
        }
        //val sp1=ime.indexOf(' ')
        //val sp2=ime.indexOf(' ', sp1+1)
        val imena=ime.split(' ')
        //if( sp2==-1) {
        if( imena.size!=3 ) {
            Toast.makeText(this, "Въведете три имена", Toast.LENGTH_SHORT).show()
            return false
        } else {
            val tv2=findViewById<TextView>(R.id.imena)
            tv2.text="Име:"+imena[0]+" Презиме:"+imena[1]+" Фамилия:"+imena[2]
        }

        return true
    }

    fun Proverka_Nomer():Boolean
    {
        val nomer=findViewById<EditText>(R.id.editTextPhone).text.toString()
        if( nomer.length==0 ) {
            Toast.makeText(this, "Липсва въведен номер", Toast.LENGTH_SHORT).show()
            return false
        }
        if( nomer.matches("[0-9]+".toRegex())==false) {
            Toast.makeText(this, "Използвайте само цифри", Toast.LENGTH_SHORT).show()
            return false
        }
        if( nomer.length!=10 || nomer.startsWith("08")==false) {
                Toast.makeText(this, "Непълен номер", Toast.LENGTH_SHORT).show()
                return false
        }
        return true
    }

    fun String.isEmailValid(): Boolean {
        return !TextUtils.isEmpty(this) && android.util.Patterns.EMAIL_ADDRESS.matcher(this).matches()
    }

    fun Proverka_Email():Boolean
    {
        val email=findViewById<EditText>(R.id.editTextTextEmailAddress).text.toString()

        /*if( email=="" ) {
            Toast.makeText(this, "Липсва въведен имейл", Toast.LENGTH_SHORT).show()
            return false
        }
        if( email.indexOfAny(charArrayOf('!','#','$','%','?',' ','=','*'))>=0 ){
            Toast.makeText(this, "Некоректни символи", Toast.LENGTH_SHORT).show()
            return false
        }
        val at=email.indexOf('@')
        val at2=email.indexOf('@',at+1)
        val dot=email.indexOf('.',at+1)
        val lastdot=email.lastIndexOf('.')
        val many=email.indexOf("..")
        if( at==-1 || dot==-1 || at2>0 || lastdot==email.length-1 || many>=0) {
            Toast.makeText(this, "Некоректен имейл", Toast.LENGTH_SHORT).show()
            return false
        }

        return true*/
        if( email.isEmailValid() ) return true
        else {
            Toast.makeText(this, "Некоректен имейл", Toast.LENGTH_SHORT).show()
            return false
        }
    }

    fun btn_check(view:View)
    {
        val chk1=findViewById<CheckBox>(R.id.checkBox)
        val chk2=findViewById<CheckBox>(R.id.checkBox2)
        val chk3=findViewById<CheckBox>(R.id.checkBox3)
        val tv=findViewById<TextView>(R.id.lbl)
        chk1.isChecked=Proverka_Ime()
        chk2.isChecked=Proverka_Nomer()
        chk3.isChecked=Proverka_Email()
        if( chk1.isChecked && chk2.isChecked && chk3.isChecked) {
            tv.text="OK"
            tv.setBackgroundColor(Color.GREEN)
        } else
        {
            tv.text="Има непопълнени полета"
            tv.setBackgroundColor(Color.RED)
        }

    }

    fun test_string()
    {
        val tv=findViewById<TextView>(R.id.lbl)
        val tmp="Здравейте"
        var rez=""
        // 1
        /*tmp.forEach {
            rez=rez+it+" "
        }*/
        // 2            tmp.length->9
        /*for( a in 0..tmp.length-1)
            //rez=rez+a.toString()+" "
            rez=rez+tmp[a]+" "*/
        // 3
        for(ch in tmp)
            rez=rez+ch+" "

        tv.text=rez
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/editTextTextPersonName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="30dp"
        android:ems="10"
        android:hint="Три имена"
        android:inputType="textPersonName"
        android:text="Ivan Petrov Minev"
        app:layout_constraintBaseline_toBaselineOf="@+id/checkBox"
        app:layout_constraintStart_toStartOf="parent" />

    <EditText
        android:id="@+id/editTextPhone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="27dp"
        android:layout_marginTop="114dp"
        android:ems="10"
        android:hint="Телефон"
        android:inputType="phone"
        android:text="0884561234"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editTextTextEmailAddress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="25dp"
        android:ems="10"
        android:hint="Имейл"
        android:inputType="textEmailAddress"
        app:layout_constraintEnd_toStartOf="@+id/button"
        app:layout_constraintStart_toStartOf="@+id/button"
        app:layout_constraintTop_toBottomOf="@+id/editTextPhone" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="27dp"
        android:layout_marginEnd="23dp"
        android:onClick="btn_check"
        android:text="Провери"
        app:layout_constraintEnd_toStartOf="@+id/checkBox3"
        app:layout_constraintTop_toBottomOf="@+id/editTextTextEmailAddress" />

    <CheckBox
        android:id="@+id/checkBox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="22dp"
        android:layout_marginBottom="16dp"
        android:editable="false"
        android:enabled="false"
        app:layout_constraintBottom_toTopOf="@+id/editTextPhone"
        app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName" />

    <CheckBox
        android:id="@+id/checkBox2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="13dp"
        android:editable="false"
        android:enabled="false"
        app:layout_constraintStart_toStartOf="@+id/checkBox"
        app:layout_constraintTop_toBottomOf="@+id/checkBox" />

    <CheckBox
        android:id="@+id/checkBox3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:editable="false"
        android:enabled="false"
        app:layout_constraintBaseline_toBaselineOf="@+id/editTextTextEmailAddress"
        app:layout_constraintStart_toStartOf="@+id/checkBox2" />

    <TextView
        android:id="@+id/lbl"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.595" />

    <TextView
        android:id="@+id/imena"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.702" />

</androidx.constraintlayout.widget.ConstraintLayout>