Lambda interfaces in Kotlin [duplicate]

Question

I have implemented this interface in my Adapter in Kotlin:

interface OnItemClickListener {
    fun onItemClick(view: View)
}

public lateinit var onItemClickListener: OnItemClickListener

public fun setItemClickListener(itemClickListener: OnItemClickListener) {
    this.onItemClickListener = itemClickListener
}

I want to use it in my Fragment with Lambda like this:

    adapter.setItemClickListener {
        // do stuff here
    }

But this error appears:

Error:(54, 39) Type mismatch: inferred type is () -> Unit but SSUpdatesAdapter.OnItemClickListener was expected

I know that I can just implement Adapter.AddOnItemTouchListener but I really want to know more about Kotlin and how to use Lambdas

pau1adam · Accepted Answer · 2018-06-19 07:50:36Z

2

The feature you are trying to use (single function interface to lambda) only works when the interface was written in Java code.

The reasoning behind this is this:

"since Kotlin has proper function types, automatic conversion of functions into implementations of Kotlin interfaces is unnecessary and therefore unsupported"

https://kotlinlang.org/docs/reference/java-interop.html#sam-conversions

answered Jun 19, 2018 at 7:50

pau1adam

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