tiptime

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.calculateButton.setOnClickListener { calculateTip() }
    }
    fun calculateTip() {
            val stringInTextField = binding.costOfService.text.toString()
            val cost = stringInTextField.toDouble()
            val selectedId = binding.tipOptions.checkedRadioButtonId
            val tipPercentage = when (selectedId) {
                R.id.option_twenty_percent -> 0.20
                R.id.option_eighteen_percent -> 0.18
                else -> 0.15
            }
            var tip = tipPercentage * cost
            val roundUp = binding.roundUpSwitch.isChecked
            if (roundUp) {
                tip = kotlin.math.ceil(tip)
            }
            NumberFormat.getCurrencyInstance()
            val formattedTip = NumberFormat.getCurrencyInstance().format(tip)
            binding.tipResult.text = getString(R.string.tip_amount, formattedTip)

    }
}

// a parte do xml com suas views

<?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"
    android:padding="16dp"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/cost_of_service"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:hint="@string/cost_of_service"
        android:inputType="numberDecimal"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:autofillHints="text" />

    <TextView
        android:id="@+id/service_question"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/how_was_the_service"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/cost_of_service" />

    <RadioGroup
        android:id="@+id/tip_options"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:checkedButton="@id/option_twenty_percent"
        android:orientation="vertical"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/service_question">

        <RadioButton
            android:id="@+id/option_twenty_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/amazing_service" />

        <RadioButton
            android:id="@+id/option_eighteen_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/good_service" />

        <RadioButton
            android:id="@+id/option_fifteen_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/okay_service" />

    </RadioGroup>

    <SwitchCompat
        android:id="@+id/round_up_switch"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:checked="true"
        android:text="@string/round_up_tip"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/tip_options" />

    <Button
        android:id="@+id/calculate_button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:text="@string/calculate"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/round_up_switch" />

    <TextView
        android:id="@+id/tip_result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        tools:text="Tip Amount: $10"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@id/calculate_button" />


</androidx.constraintlayout.widget.ConstraintLayout>

// resource com a lista de strings
<resources>
    <string name="app_name">Tip Time</string>
    <string name="amazing_service">Amazing (20%)</string>
    <string name="good_service">Good (18%)</string>
    <string name="okay_service">Okay (15%)</string>
    <string name="how_was_the_service">How was the service?</string>
    <string name="cost_of_service">Cost of Service</string>
    <string name="round_up_tip">Round up tip?</string>
    <string name="calculate">Calculate</string>
    <string name="tip_amount">Tip Amount: %s</string>
</resources>