Kotlin text validation

Question

I'm new to Kotlin, not so new to Java and Android development. But willing and trying to make a switch. I've wrote a simple validator for EditText and was wondering if there is a way to write it more compact with lambdas.

textMTU.addTextChangedListener(object : EditTextValidator(textMTU) {
 override fun validate(textView: EditText, text: String) {
 val textToInt = if (text.isEmpty()) 0 else text.toInt()
 if (textToInt < 1280 || textToInt > 1500) {
 textView.error = getString(R.string.errorTroubleshoot)
 }
 else {
 textView.error = null
 val input = if (textMTU.rawText.isEmpty()) defaultSize else textMTU.rawText.toInt()
 if (input in 1281..1499) {
 prefs.mtuSize = input
 }
 }
 }

EditTextValidator here is simply extended TextWatcher without beforeTextChanged and onTextChanged methods

Answer 1

First of all, make attention - your code twice convert and check value. Suppose it's not efficient. Another tiny problem - 1280 and 1500 values is not change prefs.mtuSize...

My code:

class MainActivity : AppCompatActivity() {
 val TAG = MainActivity::class.simpleName.toString()
 private val defaultSize = 1500
 private var prefsMtuSize: Int = defaultSize
 override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 setContentView(R.layout.activity_main)
 val textMTU = findViewById<EditText>(R.id.textMTU)
 // Extension function
 textMTU.addTextChangedListener { text ->
 val textToInt = try { text.toInt() } catch (e: NumberFormatException) { 0 }
 if (textToInt in 1280..1500) { // 1280 <= textToInt <= 1500
 textMTU.error = null
 prefsMtuSize = textToInt
 } else {
 textMTU.error = getString(R.string.errorTroubleshoot)
 prefsMtuSize = defaultSize
 }
 Log.i(TAG, "prefsMtuSize = $prefsMtuSize")
 }
 }
}
private fun EditText.addTextChangedListener(testFunction: (text: String) -> Unit) {
 addTextChangedListener(object : TextWatcher {
 override fun afterTextChanged(s: Editable?) {
 testFunction(s.toString())
 }
 override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) { }
 override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) { }
 })
}