Mobile App Dev 2021W: Tutorial 6

Code

Conversions.kt

package carleton.comp1601.converter_2a

//  Conversions.kt

class Converter {
    var convFrom = "From Type"
    var convTo = "To Type"
    var convert: (from: Double) -> Double?

    fun formatConversion(from: Double): String {
        val to = this.convert(from)
        if (to != null) {
            return "${from} ${this.convFrom} is ${to} ${this.convTo}."
        } else {
            return "Converting ${from} ${convFrom} to ${this.convTo} failed."
        }
    }

    constructor(from: String, to: String, f: (from: Double) -> Double?) {
        this.convFrom = from
        this.convTo = to
        this.convert = f
    }
}

fun InToCM(inch: Double): Double? {
    val cm = 2.54 * inch
    return cm
}

val conversions = mapOf(
        "F to C" to Converter("Farenheit", "Celsius",
            {F ->  ((F - 32.0)*(5/9))}),
        "C to F" to Converter("Celsius","Farenheit",
            {((9/5)*it + 32.0)}),
        "km to mi" to Converter("kilometers", "miles",
            fun (k: Double): Double? {
                val m = k * 0.6213712
                return m
            }),
        "inch to cm" to Converter("inches", "centimeters", ::InToCM))

MainActivity.kt

package carleton.comp1601.converter_2a

import android.os.Bundle
import android.text.Editable
import android.text.TextWatcher
import android.view.MenuItem
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.PopupMenu

class MainActivity : AppCompatActivity() {
    private lateinit var result: TextView
    private lateinit var menuButton: Button
    private lateinit var fromStringW: EditText
    private var conv: Converter? = null

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

        menuButton = findViewById(R.id.convMenu)
        fromStringW = findViewById(R.id.fromString)
        result = findViewById(R.id.result)

        fromStringW.addTextChangedListener(watcher)
        fromStringW.setVisibility(View.INVISIBLE);
    }

    fun onMenuItemClick(choice: MenuItem): Boolean {
        val convName = choice.getTitle()
        val c = conversions[convName]

        if (c != null) {
            conv = c
            result.setText("You picked ${convName}")
            fromStringW.setText("")
        } else {
            result.setText("Invalid Menu Selection")
        }

        fromStringW.setVisibility(View.VISIBLE);
        return true
    }

    // https://stackoverflow.com/questions/15580111/
    fun showMenu(v: View) {
        val menu = PopupMenu(this, v)

        for (s in conversions.keys) {
            menu.menu.add(s)
        }

        menu.setOnMenuItemClickListener(::onMenuItemClick)
        menu.show()
    }

    private val watcher = object : TextWatcher {

        override fun afterTextChanged(s: Editable) {
            val fromS = fromStringW.getText().toString()
            var from = fromS.toDoubleOrNull()

            if (from == null) {
                result.setText("Please enter a number to convert.")
            } else {
                val c = conv

                if (c != null) {
                    result.setText(c.formatConversion(from))
                } else {
                    result.setText("No conversion selected.")
                }
            }
        }

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

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