Android user input validation

Question

I have made a tiny Android-project to familiarize myself with user input validation.

The app just has an EditText-control for user input, a button "Compute Result" and a TextView, which shows the result. As input is an integer expected.

The essential part of the code:

buttonCompute.setOnClickListener {
  val strInput = inputEditText.text.toString()

  if (!TextUtils.isEmpty(strInput)) {
    val intInput = strInput.toIntOrNull()
    val result = intInput ? .times(10) ? : 0
    resultTextView.text = result.toString()
  } else {
    Toast.makeText(applicationContext, "Please provide a number!",
      Toast.LENGTH_LONG).show();
  }
}

It works, but it's a lot of code for such a small tasks.

Is there a better way? Does someone know further tricks and helpers, to accomplish the validation easier?

Answer 1

There's already a CharSequence.isNotEmpty() function in the Kotlin standard library, so you could have used that instead of !TextUtils.isEmpty(strInput). But you don't even need to check if it's empty when you're using toIntOrNull(). It will return null if the String is empty. Presumably you would want to show the user the message if they somehow entered something that is not a number (although you can set an EditText to accept only integers), so it becomes simply a null-check. The null-check also allows the value to be smart-cast inside the if-statement.

buttonCompute.setOnClickListener {
  val intInput = inputEditText.text.toString().toIntOrNull()

  if (intInput != null) {
    resultTextView.text = (intInput * 10).toString()
  } else {
    Toast.makeText(applicationContext, "Please provide a number!",
      Toast.LENGTH_LONG).show()
  }
}
```