Parameter specified as non-null is null: method ko

Question

I got this error just after converted the adapter code to Kotlin:

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter convertView
    at ...MyAdapter.getView(Unknown Source:35)
    at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220)
    at android.widget.AbsListView.obtainView(AbsListView.java:2366)

The error fires when inflating the row:

class LegalAdapter internal constructor(private val activity: Activity, private val list: ArrayList<Item>) : BaseAdapter() {

    override fun getView(position: Int, convertView: View, parent: ViewGroup): View {

    val layoutInflater = activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater

    @SuppressLint("ViewHolder")
    val row = layoutInflater.inflate(R.layout.legal_list_item, parent, false) //exception is throw here

Apparently, some parameter that shouldn't be null is null, and kotlin check it. Problem is i can't even debug the new kotlin code.

Answer 1

Make convertView nullable:

convertView: View?

I'm not sure why the line number is wrong, but the stacktrace tells you where to look in the error message.

Answer 2

The getView() method is a part of the Adapter interface, and is defined in Java. Documentation here. The important part is this note about the convertView parameter:

View: The old view to reuse, if possible. Note: You should check that this view is non-null and of an appropriate type before using.

This means that it's quite valid for the framework to pass null values for convertView to this method (meaning that you need to create a new view and return that, rather than recycling an old view).

In turn, this means that the Kotlin definition of convertView must be of type View?, not just View. So change your function signature to this:

override fun getView(position: Int, convertView: View?, parent: ViewGroup): View

Answer 3

Change your convertView in getView from non-null to nullable

override fun getView(position: Int, convertView: View, parent: ViewGroup): View {

to

override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {

Answer 4

All correct solutions are already posted above. Just one more with some code and ViewBinding:

class SpinnerAdapter(
      context: Context,
      private val items: List<YourModel>
) : BaseAdapter() {

private var layoutInflater: LayoutInflater = LayoutInflater.from(context)

override fun getView(i: Int, convertView: View?, viewGroup: ViewGroup): View {
    return if (convertView != null) {
        convertView
    } else {
        val view = layoutInflater.inflate(R.layout.item_spinner, null)
        val binding = ItemSpinnerBinding.bind(view)
        val item = items[i]
        binding.name.text = item.name
        view
    }
}

//more overridde methods
}

Where my R.layout.item_spinner has a TextView with an Id called "name".