android - Is there a way to pass a function reference between activities?

Question

is there a way of bundling function references in Kotlin and Android so that the functions can be called from other fragments? For instance, my fragment factory method looks like this:

    fun newInstance(tryAgainFunction: () -> Unit): TimeOutHandlerFragment {
        val fragment = TimeOutHandlerFragment()
        val bundle = Bundle()

        return fragment
    }

I want to be able to save my tryAgainFunction in the bundle for further retrieval.

Thanks a lot!

Edit

In the end, the most suitable solution was using hotkey's answer and then in onViewCreated I initializing a listener with the passed function. The complete code is as follows:

companion object {
    val CALLBACK_FUNCTION: String = "CALLBACK_FUNCTION"

    fun newInstance(tryAgainFunction: () -> Unit): TimeOutHandlerFragment {
        val fragment = TimeOutHandlerFragment()
        val bundle = Bundle()
        bundle.putSerializable(CALLBACK_FUNCTION, tryAgainFunction as Serializable)
        fragment.arguments = bundle
        return fragment
    }
}

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    try {
        val callback: () -> Unit = arguments.getSerializable(CALLBACK_FUNCTION) as () -> Unit
        btnTryAgain.setOnClickListener { callback.invoke() }
    } catch (ex: Exception) {
        // callback has a wrong format
        ex.printStackTrace()
    }
}

Thanks to everyone for your help!

Answer 1

If tryAgainFunction is Serializable, then you can put it into the bundle using bundle.putSerializable("try_again_function", tryAgainFunction);.

It will actually be Serializable if it is a function reference (SomeClass::someFunction) or a lambda. But it might not be, if it is some custom implementation of the functional interface () -> Unit, so you should check that and handle the cases when it's not.