Can an Activity access a Fragment to know if a button has been pressed?

Question

The Objective: I\'m trying to make a notepad application. What my app does is, a button is pressed to create a new note. This pops up a fragment in which th

Answer 1

Question 1: Is there a way by which pressing the other button in the Fragment could trigger a method in my Activity?

Sure, the simplest way to do it is:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val binding = MyFragmentBinding.bind(view) // viewBinding enabled

    binding.myButton.setOnClickListener {
        (requireActivity() as MyActivity).doSomething() // <--
    }
}

However, if this Fragment can be used in different Activity instances, then it should expose a Listener with which it exposes its potential events, and doesn't need to know the actual Activity instance it is talking to.

interface ActionHandler {
    fun onMyButtonClicked()
}

lateinit var actionHandler: ActionHandler

override fun onAttach(context: Context) {
    super.onAttach(context)
    actionHandler = context as ActionHandler
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val binding = MyFragmentBinding.bind(view) // viewBinding enabled

    binding.myButton.setOnClickListener {
        actionHandler.onMyButtonClicked()
    }
}

This way, your Fragment will always have a listener to talk to even after config changes / process death, which seems to not be the case for most other answers here.

Question 2: Would this cause the app to become too bloated? Should I keep the button within my activity itself?

This depends on whether the button actually belongs in the Activity, though it probably doesn't. Most modern apps are written as single-Activity anyway, and unless the view is shared among all screens, it's put inside a Fragment, possibly maybe even using tags from a common layout resource.