CODEWITHSUNDEEP
androidkotlinandroid-livedataandroid-viewmodel
Haddad
Haddad

Reputation: 307

android livedata Observer didn't notified

Hi guys its my first shot to livedata and i will be thankful if you help me to find whats wrong with this Observer

Observer section in my MainActivity can't receive anything, every thing is ok from my Dialogfragment and MainModel class to MainViewModel and I've got triggered logs but nothing happens to Observer in MainActivity

class MainModel {
    private var resultLiveData = MutableLiveData<List<Course>>()
    private val courseList = ArrayList<Course>()
    private val mainViewModel = MainViewModel()
    fun sum(course: Course) {
        courseList.add(course)
        resultLiveData.value = courseList
        Log.d("tag", "$course in model")
        mainViewModel.loadedResult(resultLiveData)
        Log.d("tag", "${resultLiveData.value} in my model")
    }
}

class MainViewModel : ViewModel() {
     var result = MutableLiveData<List<Course>>()

    fun loadedResult(resultData: MutableLiveData<List<Course>>) {
        result = resultData
        Log.d("tag", "main viewModel ${result.value}")
        Log.d("tag", "main viewModel ${resultData.value}")

    }
}

class MainActivity : AppCompatActivity() {

    private lateinit var fragmentManager: FragmentManager
    private lateinit var linearLayoutManager: LinearLayoutManager

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        linearLayoutManager = LinearLayoutManager(this)
        mainRecyclerView.layoutManager = linearLayoutManager
        fragmentManager = supportFragmentManager

        setupLivedata()
        floatingActionButton.setOnClickListener {
            showAddDialog()
        }
    }

    private fun setupLivedata() {
        val mainViewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
        var myList : ArrayList<Course>

        var myObserver = Observer<List<Course>> {
            observedList -> myList = observedList as ArrayList<Course>
            Log.d("tag", "${myList.size} reached main activity")
            Log.d("tag", "${observedList.size} reached main activity")

        }
        mainViewModel.result.observe(this, myObserver)
    }

    private fun showAddDialog() {
        val inputDialog = InputDialogFragment()
        inputDialog.show(supportFragmentManager, "input")
    }
}

Upvotes: 0

Views: 825

Answers (2)

seyed Jafari
seyed Jafari

Reputation: 1265

You are changing LiveData reference in MainViewModel on this line:

result = resultData

with LiveData you need to setValue/postvalue new items to actually trigger observers.

Something like this:

class MainViewModel : ViewModel() {
     val result = MediatorLiveData<List<Course>>()

    fun loadedResult(resultData: MutableLiveData<List<Course>>) {
        result.addSource(resultData, { resultObj ->
             result.setValue(resultObj);
        });
        Log.d("tag", "main viewModel ${result.value}")
        Log.d("tag", "main viewModel ${resultData.value}")

    }
}

Suggestion: better to keep LiveData immutable and not change it once created. And just update the value.

Upvotes: 1

yeonseok.seo
yeonseok.seo

Reputation: 2727

MainModel.mainViewModel and MainActivity.mainViewModel are different instances.

You shouldn't use ViewModel like this

private val mainViewModel = MainViewModel()

Upvotes: 2

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