Fragment - LiveData / LifeCycleOwner

 

MainActivity.kt

// Fragment LiveData / viewLifecyclerOwner

// https://developer.android.google.cn/codelabs/kotlin-android-training-live-data/index.html?index=..%2F..android-kotlin-fundamentals&hl=IT#4
// https://developer.android.com/topic/libraries/view-binding

class MainActivity : AppCompatActivity() {

    private lateinit var binding : ActivityMainBinding

    val manager = supportFragmentManager

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        val view = binding.root
        setContentView(view)

        binding.btn1.setOnClickListener {
            val transaction1 = manager.beginTransaction()
            val fragment1 = BlankFragment1()
            transaction1.replace(R.id.frameArea, fragment1)
            transaction1.addToBackStack(null)
            transaction1.commit()
        }

    

 

 

BlankViewModel.kt

class BlankViewModel1 : ViewModel() {

    private var _mutableCount = MutableLiveData(0)
    val liveCount : LiveData<Int>
        get() = _mutableCount


    fun plusCountValue(){
        _mutableCount.value = _mutableCount.value?.plus(1)
    }

}

 

 

BlankFragment1.kt

class BlankFragment1 : Fragment() {

    // ViewBinding + LiveData

    private val TAG = "BlankFragment1"

    private var _binding : FragmentBlank1Binding? = null
    private val binding get() = _binding!!

    private lateinit var viewModel: BlankViewModel1

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?,
    ): View? {
        // Inflate the layout for this fragment

        _binding = FragmentBlank1Binding.inflate(inflater, container, false)
        val view = binding.root

        viewModel = ViewModelProvider(this).get(BlankViewModel1::class.java)

        return view
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        binding.btn1.setOnClickListener {
            viewModel.plusCountValue()
        }

        viewModel.liveCount.observe(viewLifecycleOwner, Observer {
            binding.text1.text = it.toString()
        })

    }

    override fun onDestroyView() {
        super.onDestroyView()
        Log.d(TAG, "onDestroyView")
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d(TAG, "onDestroy")
    }


}

 

Fragment에선 생명주기가 달라 생길 수 있는 오류들을 해결하기위해 viewLifecycleOwner를 사용해야한다.

 

BlankFragment2.kt

class BlankFragment2 : Fragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_blank2, container, false)
    }


}

 

 

 

결과: