[android/kotlin] Activity,Fragment간 데이터전달

Fragment 생명주기:

• onCreate()
• onCreateView()
• onActivityCreated()
• onStart()
• onResume()
• onPause()
• onStop()
• onDestroyView()
• onDestroy()

Fragment의 데이터 전달

1. Activity → Fragment

• MainActivity.kt (보내는 코드)

  binding.run {
              fragment1Btn.setOnClickListener{
                  // [1] Activity -> FirstFragment
                  val dataToSend = "Hello First Fragment! \n From Activity"
                  val fragment = FirstFragment.newInstance(dataToSend)
                  setFragment(fragment)
              }
  
              fragment2Btn.setOnClickListener {
                  // [1] Activity -> SecondFragment
                  val dataToSend = "Hello Second Fragment!\n From Activity"
                  val fragment = SecondFragment.newInstance(dataToSend)
                  setFragment(fragment)
              }

• FirstFragment.kt (받는 코드)

  private var param1: String? = null
  
  companion object {
          @JvmStatic
          fun newInstance(param1: String) =
              // [1] Activity -> FirstFragment
              FirstFragment().apply {
                  arguments = Bundle().apply {
                      putString(ARG_PARAM1, param1)
                  }
              }
  }
  
  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
          super.onViewCreated(view, savedInstanceState)
          // [1] Activity -> FirstFragment
          binding.tvFrag1Text.text = param1     
  }

1. Fragment → Fragment

• FirstFragment.kt (보내는 코드)

  // [2] Fragment -> Fragment
          binding.btnGofrag2.setOnClickListener{
              val dataToSend = "Hello Fragment2! \n From Fragment1"
              val fragment2 = SecondFragment.newInstance(dataToSend)
              requireActivity().supportFragmentManager.beginTransaction()
                  .replace(R.id.frameLayout, fragment2)
                  .addToBackStack(null)
                  .commit()
          }

• SecondFragment.kt (받는 코드)

  
  private const val ARG_PARAM1 = "param1"
  
  class SecondFragment : Fragment() {
  
      private var param1: String? = null
  
      private var _binding: FragmentSecondBinding? = null
      private val binding get() = _binding!!
  
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          arguments?.let {
              param1 = it.getString(ARG_PARAM1)
          }
      }
  
      override fun onCreateView(
          inflater: LayoutInflater, container: ViewGroup?,
          savedInstanceState: Bundle?
      ): View {
          _binding = FragmentSecondBinding.inflate(inflater, container, false)
          return binding.root
      }
  
      override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
          super.onViewCreated(view, savedInstanceState)
          // [2] Fragment -> Fragment
          binding.tvFrag2Text.text = param1
      }
  
      companion object {
          @JvmStatic
          fun newInstance(param1: String) =
              // [1] Activity -> FirstFragment
              SecondFragment().apply {
                  arguments = Bundle().apply {
                      putString(ARG_PARAM1, param1)
                  }
              }
      }
  
      override fun onDestroyView() {
          super.onDestroyView()
          // Binding 객체 해제
          _binding = null
      }
  }

1. Fragment → Activity

• SecondFragment.kt (보내는 코드)

  private const val ARG_PARAM1 = "param1"
  
  interface FragmentDataListener {
      fun onDataReceived(data: String)
  }
  
  class SecondFragment : Fragment() {
  
      // [3] SecondFragment -> Activity
      private var listener: FragmentDataListener? = null
  
      private var param1: String? = null
  
      private var _binding: FragmentSecondBinding? = null
      private val binding get() = _binding!!
  
      override fun onAttach(context: Context) {
          super.onAttach(context)
  
          // [3] SecondFragment -> Activity
          if (context is FragmentDataListener) {
              listener = context
          } else {
              throw RuntimeException("$context must implement FragmentDataListener")
          }
      }
  
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
  
          arguments?.let {
              param1 = it.getString(ARG_PARAM1)
          }
      }
  
      override fun onCreateView(
          inflater: LayoutInflater, container: ViewGroup?,
          savedInstanceState: Bundle?
      ): View {
          _binding = FragmentSecondBinding.inflate(inflater, container, false)
          return binding.root
      }
  
      override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
          super.onViewCreated(view, savedInstanceState)
          // [2] Fragment -> Fragment
          binding.tvFrag2Text.text = param1
  
          // [3] SecondFragment -> Activity
          binding.btnSendActivity.setOnClickListener{
              val dataToSend = "Hello from SecondFragment!"
              listener?.onDataReceived(dataToSend)
          }
      }
  
      companion object {
          @JvmStatic
          fun newInstance(param1: String) =
              // [1] Activity -> FirstFragment
              SecondFragment().apply {
                  arguments = Bundle().apply {
                      putString(ARG_PARAM1, param1)
                  }
              }
      }
  
      override fun onDestroyView() {
          super.onDestroyView()
          // Binding 객체 해제
          _binding = null
          listener = null
      }
  }

• MainActivity.kt (받는 코드)

  class MainActivity : AppCompatActivity(), FragmentDataListener {
  
      private val binding by lazy { ActivityMainBinding.inflate(layoutInflater) }
  
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          setContentView(binding.root)
  
          binding.run {
              fragment1Btn.setOnClickListener{
                  // [1] Activity -> FirstFragment
                  val dataToSend = "Hello First Fragment! \n From Activity"
                  val fragment = FirstFragment.newInstance(dataToSend)
                  setFragment(fragment)
              }
  
              fragment2Btn.setOnClickListener {
                  // [1] Activity -> SecondFragment
                  val dataToSend = "Hello Second Fragment!\n From Activity"
                  val fragment = SecondFragment.newInstance(dataToSend)
                  setFragment(fragment)
              }
          }
  
          setFragment(FirstFragment())
      }
  
      private fun setFragment(frag : Fragment) {
          supportFragmentManager.commit {
              replace(R.id.frameLayout, frag)
              setReorderingAllowed(true)
              addToBackStack("")
          }
      }
  
      // [3] SecondFragment -> Activity
      override fun onDataReceived(data: String) {
          // Fragment에서 받은 데이터를 처리
          Toast.makeText(this, data, Toast.LENGTH_SHORT).show()
      }
  }