CODEWITHSUNDEEP
androidandroid-fragmentslambdainterfacekotlin
Gabi Moreno
Gabi Moreno

Reputation: 881

Listener between Fragment and Fragment (or Activity)

Is there any better clean way to put a listener inside a Fragment?

class FooFragment : Fragment() {

    companion object {
        private lateinit var listener: (Int) -> Unit

        fun newInstance(listener: (Int) -> Unit): FooFragment {
            Companion.listener = listener
            return FooFragment()
        }
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_foo, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        btn.setOnClickListener {
            listener(1234)
        }
    }
}

The call is so tidy...

FooFragment.newInstance {
    // Do something
}

I know this code have problems due to maybe I lose the listener when the Fragment is recreated and that the standard way is using the onAttach(context: Context?) way.

But I want to create a new instance of the FooFragment from other Fragment (not an Activity). I could use something like this:

private var listener: Listener? = null

interface Listener {
    fun onFooClicked()
}

override fun onAttach(context: Context?) {
    super.onAttach(context)
    // listener = context as Listener
    fragmentManager?.findFragmentById(R.id.fFooParent) as Listener
}

But this piece of code inside the onAttach(context: Context?) method inside the FooFragment, would be counterproductive due to I do not want that the FooFragment knows anything of the class who insntantiates it. Moreover, I would like that it could be a Fragment or an Activity.

Upvotes: 3

Views: 1493

Answers (1)

Pavneet_Singh
Pavneet_Singh

Reputation: 37404

You can crate a baseActivity which implements the listener 

class BaseFragmentActivity:AppCompatActivity(), FooFragment.Listener{}

then extend class YouFragmentActivity : BaseFragmentActivity

then it will make sure that every fragment hosting activity is equipped with container then you can get the reference as BaseFragmentActivity

You can replace AppCompatActivity with BaseActivity where BaseActivity :AppCompatActivity

Upvotes: 2

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