Cannot create an instance of class com.ma.todo.data.viewmodel.ToDoViewModel

Question

I was creating a simple todoapp. when try to create a viewmodel. I got exception and app crashed.

java.lang.RuntimeException: Cannot create an instance of class com.ma.todo2.data.viewmodel.ToDoViewModel
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:322)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:306)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:280)
                                                                                                        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:128)
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:187)
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:153)
                                                                                                        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:53)
                                                                                                        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:35)
                                                                                                        at com.mahi.todo2.fragments.add.AddFragment.getMToDoViewModel(AddFragment.kt:31)
                                                                                                        at com.mahi.todo2.fragments.add.AddFragment.insertDataToDb(AddFragment.kt:78)
                                                                                                        at com.mahi.todo2.fragments.add.AddFragment.onOptionsItemSelected(AddFragment.kt:61)

line 31,


    private val mToDoViewModel: ToDoViewModel by viewModels()

why this happens? what is the solution?

TodoViewModel


class ToDoViewModel(application: Application): AndroidViewModel(application)
{
    private val toDoDao = ToDoDatabase.getDatabase(application).toDoDao()
    private val repository: ToDoRepository

    private val getAllData: LiveData<List<ToDoData>>

    init {
        repository = ToDoRepository(toDoDao)
        getAllData = repository.getAllData
    }

    fun insertData(toDoData: ToDoData){
        viewModelScope.launch(Dispatchers.IO) {
            repository.insertData(toDoData)
        }
    }
}

AddFragment

class AddFragment : Fragment() {

    private lateinit var title_et: EditText
    private lateinit var priorities_spinner: Spinner
    private lateinit var description_et : EditText

    private val mToDoViewModel: ToDoViewModel by viewModels()
    private val mSharedViewModel: SharedViewModel by viewModels()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        // Inflate the layout for this fragment
      val view = inflater.inflate(R.layout.fragment_add, container, false)

      setHasOptionsMenu(true)

      title_et =  view.findViewById<EditText>(R.id.title_et)
      priorities_spinner  = view.findViewById<Spinner>(R.id.priorities_spinner)
      description_et = view.findViewById<EditText>(R.id.description_et)

      priorities_spinner.onItemSelectedListener = mSharedViewModel.listener

      return view

    }

    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
        inflater.inflate(R.menu.add_fragment_menu, menu)
        super.onCreateOptionsMenu(menu, inflater)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        if(item.itemId == R.id.menu_add){
            insertDataToDb()
        }
        return super.onOptionsItemSelected(item)
    }

    private fun insertDataToDb(){

        val mTitle = title_et.text.toString()
        val mPriority = priorities_spinner.selectedItem.toString()
        val mDescription = description_et.text.toString()

        val validation = mSharedViewModel.verifyDataFromUser(mTitle, mDescription)

        if(validation){
            //iinsert data to database
            val newData = ToDoData(0, mTitle, mSharedViewModel.parsePriority(mPriority), mDescription)

            mToDoViewModel.insertData(newData)
            Toast.makeText(requireContext(), "Successfully added!", Toast.LENGTH_SHORT).show()
            //Navigate back
            findNavController().navigate(R.id.action_addFragment_to_listFragment)
        }
        else{
            Toast.makeText(requireContext(), "Please fill out all fields.", Toast.LENGTH_SHORT).show() 
        }

    }


}

private val mToDoViewModel: ToDoViewModel by lazy { ViewModelProvider(this).get(ToDoViewModel::class.java) } you can check by doing lazy intialization also for viewmodel. — Saif Khan, Aug 30 '23 at 08:17

score 0 · Answer 1 · answered Aug 30 '23 at 13:40

The problem is you aren’t passing the parameter to your veiwModel to instantiate it.

From this question you can use something like this to pass parameters:

val viewModel: MyViewModel by viewModels { MyViewModelFactory(getApplication(), "my awesome param") }

Please see the other question for how to make the factory.

Cannot create an instance of class com.ma.todo.data.viewmodel.ToDoViewModel

1 Answers1