Unit Conversion Application Main_Activity file

MainActivity.kt

package com.example.unitconversionapplication

import android.os.Bundle
import androidx.activity.enableEdgeToEdge
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.ViewCompat
import androidx.core.view.WindowInsetsCompat
import android.text.Editable
import android.text.TextWatcher
import android.widget.*

class MainActivity : AppCompatActivity() {

    private lateinit var inputBox: EditText
    private lateinit var outputBox: TextView
    private lateinit var unitTypeGroup: RadioGroup
    private lateinit var lengthUnitSpinner1: Spinner
    private lateinit var lengthUnitSpinner2: Spinner
    private lateinit var temperatureUnitSpinner1: Spinner
    private lateinit var temperatureUnitSpinner2: Spinner

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

        inputBox = findViewById(R.id.inputBox)
        outputBox = findViewById(R.id.outputBox)
        unitTypeGroup = findViewById(R.id.unitTypeGroup)
        lengthUnitSpinner1 = findViewById(R.id.lengthUnitSpinner1)
        lengthUnitSpinner2 = findViewById(R.id.lengthUnitSpinner2)
        temperatureUnitSpinner1 = findViewById(R.id.temperatureUnitSpinner1)
        temperatureUnitSpinner2 = findViewById(R.id.temperatureUnitSpinner2)

        // Set up radio button change listener
        unitTypeGroup.setOnCheckedChangeListener { _, checkedId ->
            when (checkedId) {
                R.id.lengthRadioButton -> {
                    lengthUnitSpinner1.visibility = Spinner.VISIBLE
                    lengthUnitSpinner2.visibility = Spinner.VISIBLE
                    temperatureUnitSpinner1.visibility = Spinner.GONE
                    temperatureUnitSpinner2.visibility = Spinner.GONE
                }
                R.id.temperatureRadioButton -> {
                    lengthUnitSpinner1.visibility = Spinner.GONE
                    lengthUnitSpinner2.visibility = Spinner.GONE
                    temperatureUnitSpinner1.visibility = Spinner.VISIBLE
                    temperatureUnitSpinner2.visibility = Spinner.VISIBLE
                }
            }
        }

        // Set up input box listener to perform conversions
        inputBox.addTextChangedListener(object : TextWatcher {
            override fun afterTextChanged(s: Editable?) {
                performConversion()
            }

            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}
            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
        })
    }

    private fun performConversion() {
        val inputText = inputBox.text.toString()
        if (inputText.isNotEmpty()) {
            val inputValue = inputText.toDoubleOrNull() ?: return
            val outputValue = when (unitTypeGroup.checkedRadioButtonId) {
                R.id.lengthRadioButton -> convertLength(inputValue)
                R.id.temperatureRadioButton -> convertTemperature(inputValue)
                else -> null
            }
            outputBox.text = outputValue?.toString() ?: ""
        } else {
            outputBox.text = ""
        }
    }

    private fun convertLength(value: Double): Double? {
        val fromUnit = lengthUnitSpinner1.selectedItem.toString()
        val toUnit = lengthUnitSpinner2.selectedItem.toString()

        val baseValue = when (fromUnit) {
            "m" -> value
            "km" -> value * 1000
            "inches" -> value * 0.0254
            "feet" -> value * 0.3048
            else -> return null
        }

        return when (toUnit) {
            "m" -> baseValue
            "km" -> baseValue / 1000
            "inches" -> baseValue / 0.0254
            "feet" -> baseValue / 0.3048
            else -> null
        }
    }

    private fun convertTemperature(value: Double): Double? {
        val fromUnit = temperatureUnitSpinner1.selectedItem.toString()
        val toUnit = temperatureUnitSpinner2.selectedItem.toString()

        return when (fromUnit to toUnit) {
            "centigrade" to "fahrenheit" -> (value * 9/5) + 32
            "fahrenheit" to "centigrade" -> (value - 32) * 5/9
            else -> value // if fromUnit == toUnit
        }
    }
}