package com.example.simplecalculator
import android.os.Bundle
import android.widget.*
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val firstNumberInput = findViewById<EditText>(R.id.firstNumber)
val secondNumberInput = findViewById<EditText>(R.id.secondNumber)
val operationsGroup = findViewById<RadioGroup>(R.id.operationsGroup)
val calculateButton = findViewById<Button>(R.id.calculateButton)
val resultView = findViewById<TextView>(R.id.resultView)
fun add(a: Double, b: Double) = a + b
fun subtract(a: Double, b: Double) = a - b
fun multiply(a: Double, b: Double) = a * b
fun divide(a: Double, b: Double) = if (b != 0.0) a / b else Double.NaN
val operationLambda: (Double, Double) -> Double = { a, b ->
when (operationsGroup.checkedRadioButtonId) {
R.id.addRadio -> add(a, b)
R.id.subtractRadio -> subtract(a, b)
R.id.multiplyRadio -> multiply(a, b)
R.id.divideRadio -> divide(a, b)
else -> Double.NaN
}
}
calculateButton.setOnClickListener {
val num1 = firstNumberInput.text.toString().toDoubleOrNull()
val num2 = secondNumberInput.text.toString().toDoubleOrNull()
if (num1 == null || num2 == null) {
Toast.makeText(this, "Please enter valid numbers", Toast.LENGTH_SHORT).show()
return@setOnClickListener
}
val result = operationLambda(num1, num2)
if (result.isNaN()) {
resultView.text = "Error: Cannot divide by zero"
} else {
resultView.text = "Result: $result"
}
}
}
}This app screen lets the user enter two numbers and pick an operation using radio buttons. We define four simple functions: add, subtract, multiply, and divide. Each takes two numbers and returns the result.
We then create a lambda called operationLambda that uses a when expression to check which radio button is selected. It calls the matching function accordingly.
When the user taps the Calculate button, we read the numbers safely using toDoubleOrNull(). If inputs are invalid, we show a toast message.
If inputs are valid, we call the lambda with the two numbers and display the result. We handle division by zero by returning Double.NaN and showing an error message.
This approach cleanly separates the operations into functions and uses a lambda to pick the right one based on user choice, demonstrating Kotlin functions and lambdas in a simple app.
