Activity - Fragment 간 Communication

1. Fragment -> Activity

fragment의 버튼을 누르면 "까꿍" string이 activity의 TextView에 표시

TestFragment.kt

class TestFragment : Fragment() {

    private lateinit var fragment_btn: Button
    private lateinit var fragment_tv: TextView

    private var listener: OnFragmentInteractionListener? = null

    override fun onAttach(context: Context) {
        super.onAttach(context)

        if (context is OnFragmentInteractionListener) {
            listener = context
        } else {
            throw RuntimeException(context.toString() + " must implement OnFragmentInteractionListener")
        }
    }

...

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    val view =  inflater.inflate(R.layout.fragment_test, container, false)
    fragment_tv = view.findViewById(R.id.fragment_tv)

    fragment_btn.setOnClickListener {
        istener?.onFragmentInteraction(msg)
    }
    return view
}

interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    fun onFragmentInteraction(msg: String)
}

MainActivity.kt

class MainActivity : AppCompatActivity(), TestFragment.OnFragmentInteractionListener {



    override fun onFragmentInteraction(msg: String) {
        activity_tv.text = msg
    }

    private val fragment: TestFragment by lazy { TestFragment() }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //프레그먼트
        supportFragmentManager.beginTransaction()
            .add(R.id.fragment_container, fragment)
            .commit()

    }
}

2. Activity -> Fragment

activity의 버튼 누르면 Fragment의 textview에 "까꿍!"표시.

프레그먼트에 함수 하나 만든 다음에 Activity에서 호출하면 된다.

//프레그먼트의 함수호출
activity_btn.setOnClickListener {
    fragment.setMsg("까꿍!")
}

activity에서 호출

fun setMsg(msg:String){
    fragment_tv.text = msg
}

fragment의 함수

전체코드

MainActivity

class MainActivity : AppCompatActivity(), TestFragment.OnFragmentInteractionListener {


    //프레그먼트에서 온 값
    override fun onFragmentInteraction(msg: String) {
        activity_tv.text = msg
    }

    private val fragment: TestFragment by lazy { TestFragment() }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //프레그먼트
        supportFragmentManager.beginTransaction()
            .add(R.id.fragment_container, fragment)
            .commit()


        //프레그먼트의 함수호출
        activity_btn.setOnClickListener {
            fragment.setMsg("까꿍!")
        }
        
    }
}

TestFragment (Android Stuio에서 BlankFragmnet로 생성된 코드 기반)

// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"

/**
 * A simple [Fragment] subclass.
 * Activities that contain this fragment must implement the
 * [BlankFragment.OnFragmentInteractionListener] interface
 * to handle interaction events.
 * Use the [BlankFragment.newInstance] factory method to
 * create an instance of this fragment.
 *
 */


class TestFragment : Fragment() {

    private lateinit var fragment_btn: Button
    private lateinit var fragment_tv: TextView

    // TODO: Rename and change types of parameters
    private var param1: String? = null
    private var param2: String? = null
    private var listener: OnFragmentInteractionListener? = null


    override fun onAttach(context: Context) {
        super.onAttach(context)

        if (context is OnFragmentInteractionListener) {
            listener = context
        } else {
            throw RuntimeException(context.toString() + " must implement OnFragmentInteractionListener")
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        arguments?.let {
            param1 = it.getString(ARG_PARAM1)
            param2 = it.getString(ARG_PARAM2)
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        val view =  inflater.inflate(R.layout.fragment_test, container, false)

        fragment_btn = view.findViewById(R.id.fragment_btn)
        fragment_tv = view.findViewById(R.id.fragment_tv)

        fragment_btn.setOnClickListener {
            onButtonPressed("까꿍")
        }
        return view
    }

    // TODO: Rename method, update argument and hook method into UI event
    fun onButtonPressed(msg: String) {
        listener?.onFragmentInteraction(msg)
    }


    override fun onDetach() {
        super.onDetach()
        listener = null
    }


    fun setMsg(msg:String){
        fragment_tv.text = msg
    }


    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     *
     *
     * See the Android Training lesson [Communicating with Other Fragments]
     * (http://developer.android.com/training/basics/fragments/communicating.html)
     * for more information.
     */
    interface OnFragmentInteractionListener {

        fun onFragmentInteraction(msg: String)
    }


    companion object {
        /**
         * Use this factory method to create a new instance of
         * this fragment using the provided parameters.
         *
         * @param param1 Parameter 1.
         * @param param2 Parameter 2.
         * @return A new instance of fragment BlankFragment.
         */
        // TODO: Rename and change types and number of parameters
        @JvmStatic
        fun newInstance(param1: String, param2: String) =
            TestFragment().apply {
                arguments = Bundle().apply {
                    putString(ARG_PARAM1, param1)
                    putString(ARG_PARAM2, param2)
                }
            }
    }
}