Упражнение 3. Използване на контроли

<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" />

<ImageView
    android:id="@+id/imageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="34dp"
    android:layout_marginTop="16dp"
    android:onClick="btn_Pict"
    android:tag="0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:srcCompat="@drawable/sv1" />

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="33dp"
    android:layout_marginEnd="84dp"
    android:onClick="btn_Pict"
    android:text="Button"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Switch
    android:id="@+id/switch1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="156dp"
    android:layout_marginEnd="72dp"
    android:text="Switch"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<RatingBar
    android:id="@+id/ratingBar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="52dp"
    android:layout_marginEnd="21dp"
    android:numStars="4"
    app:layout_constraintEnd_toEndOf="@+id/switch1"
    app:layout_constraintTop_toBottomOf="@+id/switch1" />


import android.graphics.Color
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.webkit.WebView
import android.widget.*
import androidx.core.view.isVisible

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

        findViewById<Switch>(R.id.switch1).setOnClickListener {
            val sw=findViewById<Switch>(R.id.switch1)
            val iv=findViewById<ImageView>(R.id.imageView)
            iv.isVisible=sw.isChecked
            if( sw.isChecked )
                Toast.makeText(this, "ON", Toast.LENGTH_SHORT).show()
            else
                Toast.makeText(this, "OFF", Toast.LENGTH_SHORT).show()
        }
        findViewById<RatingBar>(R.id.ratingBar).setOnRatingBarChangeListener { ratingBar, fl, b ->
            //val rb=findViewById<RatingBar>(R.id.ratingBar)
            val tv=findViewById<TextView>(R.id.lbl)
            //val st=rb.rating
            //tv.text="Стойност: "+st.toString()
            //tv.text="Стойност: "+fl.toString()
            //1 Вариант
            /*if(fl<=1) tv.text="Една звезда"
            else if(fl<=2) tv.text="Две звезда"
            else if(fl<=3) tv.text="Три звезда"
            else tv.text="Четири звезда"*/
            //2 Вариант
            /*when((fl-0.5).toInt()) {
                0-> tv.text="Една звезда"
                1->tv.text="Две звезда"
                2->tv.text="Три звезда"
                3->tv.text="Четири звезда"
            }*/
            //3 Вариант
            val imena= listOf("Една звезда","Две звезда","Три звезда","Четири звезда")
            tv.text=imena[(fl-0.5).toInt()]
            if( fl!=fl.toInt().toFloat()) tv.text=tv.text.toString()+" и половина"
        }

    }

    fun btn_Pict(view: View)
    {
        val tv=findViewById<TextView>(R.id.lbl)
        val iv=findViewById<ImageView>(R.id.imageView)
        iv.tag=iv.tag.toString().toInt()+1
        if(iv.tag==3 ) iv.tag=0

        when(iv.tag) {
            0-> {
                iv.setImageResource(R.drawable.sv1)
                tv.text="Зелено"
                tv.setBackgroundColor(Color.GREEN)
            }
            1->{
                iv.setImageResource(R.drawable.sv2)
                tv.text="Жълто"
                tv.setBackgroundColor(Color.YELLOW)
            }
            2->{
                iv.setImageResource(R.drawable.sv3)
                tv.text="Червено"
                tv.setBackgroundColor(Color.RED)
            }
        }
        /*if( iv.tag==0 ) {
            iv.setImageResource(R.drawable.sv1)
            tv.text="Зелено"
        }
        if( iv.tag==1 ) {
            iv.setImageResource(R.drawable.sv2)
            tv.text="Жълто"
        }
        if( iv.tag==2 ) {
            iv.setImageResource(R.drawable.sv3)
            tv.text="Червено"
        }*/
    }
}