App crashes when I click a Button if EditText is empty - android-studio

Question

I wrote a simple temperature converter app, everything is working fine except when user leaves EditText blank/null but selects one of the radio buttons, The App crashes.
Here is the Kotlin Code:
class MainActivity : AppCompatActivity() {
lateinit var etTemp: EditText
lateinit var radioGroup: RadioGroup
lateinit var btnConverter :Button
lateinit var tempConverted: TextView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
title = "Zeeshan's Temperature Converter"
etTemp = findViewById(R.id.etTemp)
radioGroup = findViewById(R.id.radioGroup)
btnConverter = findViewById(R.id.btnConverter)
tempConverted = findViewById(R.id.tempConverted)
btnConverter.setOnClickListener {
val id = radioGroup.checkedRadioButtonId
val radioButton = findViewById<RadioButton>(id)
if (radioButton == findViewById(R.id.radioC)){
val temp =etTemp.text.toString().toInt()
val result = temp * 9/5 + 32
tempConverted.setText(result.toString())
}
else if (radioButton == findViewById(R.id.radioF)){
val tempy =etTemp.text.toString().toInt()
val resulty = (tempy - 32) / 1.8
tempConverted.setText(resulty.toString())
}
else{
Toast.makeText(this#MainActivity, "Select one conversion scale", Toast.LENGTH_SHORT).show()
}
}
}
}

Answer 1

You should check if etTemp.text.ToString() == "" (that is empty string) if it is, then do not try to convert it into int. The problem appears when you try to convert "null" value to int.

Answer 2

Inside the listener add a check for for EditText to check whether it is empty or not,
btnConverter.setOnClickListener {
// Add the validation check here ... like this -> if(etTemp.length() > 0){
val id = radioGroup.checkedRadioButtonId
val radioButton = findViewById<RadioButton>(id)
if (radioButton == findViewById(R.id.radioC)){
val temp =etTemp.text.toString().toInt()
val result = temp * 9/5 + 32
tempConverted.setText(result.toString())
}
else if (radioButton == findViewById(R.id.radioF)){
val tempy =etTemp.text.toString().toInt()
val resulty = (tempy - 32) / 1.8
tempConverted.setText(resulty.toString())
}
else{
Toast.makeText(this#MainActivity, "Select one conversion scale", Toast.LENGTH_SHORT).show()
}
// Close the check here -> }
else{
// Prompt the user to put some text in the field - this is called form validation before processing
// Toast.makeText(.....).show
}
}

Answer 3

check if the user has entered some input or not, one way is like below (Kotlin):
if(!etTemp.text.isNullOrEmpty())
{
temp =etTemp.text.toString().toInt()
}