create method of DataSource.Factory doesn't get call

Question

Im trying to make a dictionary application with Paging library. when a user writes any letters, I will call an API and get all the words including that letter.

The problem is that, when I call the API via the Paging library in the init{} method of my ViewHolder, it works perfectly. but after that, when I try to write something else and get relevant data, Paging library doesn't even call the API. I put breakpoints every where, and I saw that after the first time, the create() method of DataSource.Factory doesn't get call.

here is my code :

My Activity :

    viewModel = ViewModelProviders.of(this).get(DictionaryViewModel::class.java)
    val adapter = DictionaryRecyclerPagedAdapter()
    recycler.layoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL, false)
    recycler.setHasFixedSize(true)
    recycler.adapter = adapter

    RxTextView.textChanges(edtWord)
        .filter { it.isNotBlank() }
        .subscribe({
            adapter.submitList(null)
            viewModel.getWord(it.toString())
            Logger.d(it)

        }, {
            Logger.d(it)
        })



    viewModel.itemPagedList?.observe(this, Observer {
        adapter.submitList(it)
    })

My ViewModel :

var liveDataSource: LiveData<PageKeyedDataSource<Int, DictionaryResult>>? = null
var itemPagedList: LiveData<PagedList<DictionaryResult>>? = null

init {

    getWord("pouya")
}

fun getWord(term: String) {

    val dataSourceFactory = DictionaryDataFactory(term)
    liveDataSource = dataSourceFactory.liveData


    val config = PagedList.Config.Builder()
        .setEnablePlaceholders(true)
        .setPageSize(10)
        .setPrefetchDistance(4)
        .build()

    itemPagedList = LivePagedListBuilder(dataSourceFactory, config).build()

}

My DataSource :

   class DictionaryDataSource(private val term: String) : PageKeyedDataSource<Int, DictionaryResult>() {

override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, DictionaryResult>) {
    Logger.d("Initial")
    composite.add(
        repository.getWord(FIRST_PAGE, term)
            .subscribe({
                if (it.result != null)
                    callback.onResult(it.result, null, FIRST_PAGE + 1)
            }, {
                Logger.d(it)

            })
    )
}

override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, DictionaryResult>) {
    Logger.d("AFTER")
    composite.add(repository.getWord(params.key, term)
        .subscribe({
            if (it.result != null)
                callback.onResult(it.result, params.key + 1)
        }, {
            Logger.d(it)
        })
      )

    }

}

My DataSource.Factory :

  class DictionaryDataFactory(private val term: String) : DataSource.Factory<Int, DictionaryResult>() {

val liveData = MutableLiveData<PageKeyedDataSource<Int, DictionaryResult>>()

override fun create(): DataSource<Int, DictionaryResult> {
    val dataSource = DictionaryDataSource(term)
    liveData.postValue(dataSource)
    return dataSource
    }
 }

So just have this in mind that it works perfectly as soon as I launch the app (it gets all the meanings for the word "pouya" as I called it in init{} method of my ViewHolder) but afterward, when I write something in the edittext, all the needed methods get called, except create() method of DataSource.Factory.

any helps would be appreciated.

Answer 1

I have faced the same problem , what solved it for me was to build the list before setting observers , in your case make sure getWord() is called before itemPagedList is observed on

For example :- Here's a snippet from a fragment which uses viewModel.reponseList

override fun onViewReady() {
    setRecyclerView()
    viewModel.buildResponseList() //For some reason responseList must be built before observing on it ,
    // otherwise create() in FoodDataSourceFactory won't be called
    setObservers()
}

private fun setObservers() {
    viewModel.responseList.observe(this, Observer {
        (this.rvFoodList.adapter as FoodListAdapter).submitList(it)
    })
}

private fun setRecyclerView() {
    val mRecyclerView = this.rvFoodList
    mRecyclerView.apply {
        layoutManager = LinearLayoutManager([email protected])
        adapter = FoodListAdapter()
    }

ViewModel Part : -

fun buildResponseList() {
    val foodDataSourceFactory =
        FoodDataSourceFactory(this)

    val config = PagedList.Config.Builder()
        .setInitialLoadSizeHint(30)
        .setEnablePlaceholders(false)
        .setPageSize(30)
        .build()

    responseList = LivePagedListBuilder(foodDataSourceFactory, config).build()
}

in onViewReady()

if I setObservers() before I call viewModel.buildResponseList()

DataSourceFactory class won't call create() method thus not making network call in DataSource class