Kotlin Object Values from API Response as Spinner Options

Question

I am unfortunately still quite new to Kotlin and Android.

I get a list of objects via API and want to display each list item as an option in the spinner to make a new API request based on it.

My API response looks something like this:

[User(username=a, id=1, [email protected]), 
User(username=b, id=2, [email protected]), 
User(username=c, id=3, [email protected])]

I just want to display all usernames in a spinner and when a username is selected start another API request with the ID of the selected user.

Unfortunately, I didn't find any way in the Kotlin Spinner doc and googling to set the options of a spinner in my fragment to select the name and store the ID in a variable.

Is there any way to do something like this in Kotlin without much effort or am I thinking wrong?

Answer 1

You can pass a list of Users to an ArrayAdapter:

val list: MutableList<User> = arrayListOf(
        User("a", 1, "[email protected]"),
        User("b", 2, "[email protected]"),
        User("c", 3, "[email protected]"),
        User("d", 4, "[email protected]")
    )

val arrayAdapter = ArrayAdapter(
        this,
        android.R.layout.simple_list_item_1,
        list
    )

Set the adapter to your spinner:

val spinner = findViewById<Spinner>(R.id.spinner)
spinner.adapter = arrayAdapter

Then depents your logic you can add a Button and inside it's click listener you can pick the whole selected user object:

button.setOnClickListener {
    //Here you have the selected user with it's id
    val selectedUser = spinner.selectedItem as User
}

Or you can set an on item selected listener and pick again the whole user object:

spinner.onItemSelectedListener =  object: AdapterView.OnItemSelectedListener {
        override fun onItemSelected(
            parent: AdapterView<*>?,
            view: View?,
            position: Int,
            id: Long
        ) {
            if (parent is Spinner) {
                //Here you have the selected user with it's id
                val selectedUser = parent.selectedItem as User
                
            }
        }

        override fun onNothingSelected(parent: AdapterView<*>?) {
            TODO("Not yet implemented")
        }
    }

Now to make the spinner diplay the username just overide the toString() function in your User class and return the username:

class User(val username: String, val id: Int, val email: String) {
    override fun toString(): String {
        return username
    }
}

I hope it was what you were looking for. Also because I am new to software development I would like to see some feedback from more experienced people on whether this approach is good or not.