为什么我不能在 Android Studio 中将函数的结果绑定到我的 TextView？

Question

I'm trying to self-teach Kotlin with the Google Android Dev Courses (I started a week ago and have very little experience in coding).
At the end of the course that thaught me to build a working Tip Calculator, there was an optional exercise to create a similar app.
I chose to create an Animal Age Calculator but i can't manage to bind the result to its TextView.

The output that i get is Animal age: %s .
The ouput that i want is the result of either my catAgeFormula(age) or my dogAgeFormula(age)
I understand it's showing me this : <string name="animal_age">Animal age: %s</string>
But the thing i don't understand is why my binding doesn't work binding.ageResult.text = getString(R.string.animal_age)

Here is the complete function i'm not sure about :

private fun calculateAge() {
    val stringInTextField = binding.userAge.text.toString()
    val age = stringInTextField.toIntOrNull()

    if (age == null || age == 0) {
        binding.ageResult.text = "0"
        return
    }

    when (binding.animalOptions.checkedRadioButtonId) {
    R.id.option_cat -> catAgeFormula(age)
    else -> dogAgeFormula(age)
    }

    binding.ageResult.text = getString(R.string.animal_age)
}

And the output TextView :

<TextView
    android:id="@+id/age_result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toBottomOf="@id/calculate_button"
    tools:text="Animal age : 42 years" />

This is my first post on Stack Overflow so i'm really sorry if messed up something.
Thanks in advance for you help :)

Answer 1

You are missing an argument on the getString method

private fun calculateAge() {
    val stringInTextField = binding.userAge.text.toString()
    //...
    binding.ageResult.text = getString(R.string.animal_age, stringInTextField)
}

Your string is:

<string name="animal_age">Animal age: %s</string>

The %s means it expects to receive 1 String type argument. The method getString can receive 2 arguments. The first is the id of the resource string and the second a vararg that can be any number of other arguments. This is because a string defined on the resources can take up any number of other arguments, by example:

<string name="example">Example %1$s %2$d</string>

Where %2$d it would be a number expected as a second argument

val example = getString(R.string.example, "one", 2)
//Example one 2

You can refer to the official documentation for further explanations

Answer 2

Thanks to cutiko, i found out i was missing a variable for the code to work properly.
I added my when statement into a variable named animalAge and used it as a second argument to my getString method.

Here is the final working function :

private fun calculateAge() {
    val stringInTextField = binding.userAge.text.toString()
    val age = stringInTextField.toIntOrNull()
    //...
    val animalAge = when (binding.animalOptions.checkedRadioButtonId) {
        R.id.option_cat -> catAgeFormula(age)
        else -> dogAgeFormula(age)
    }
    binding.ageResult.text = getString(R.string.animal_age, animalAge)
}

And the final working string resource :

<string name="animal_age">Animal age: %d</string>