neilcannon / mvvmdialogs

MvvmDialogs

A little library to reduce the boilerplate involved with creating Android dialogs using MVVM Live Events. Handles creating the DialogFragment using AlertDialog and provides base MVVM Events.

Background

When using the MVVM architecture, DialogFragments should communicate with their host Activity or Fragment using a shared ViewModel (in the Activity's scope). Dialog events (button clicks or user cancellation) need to be modelled as Live Events, rather than as state that persists across configuration changes.

Example

class SimplestDialogFragment : StandardAlertDialogFragment() {

    class SimplestViewModel : StandardDialogViewModel()

    override val viewModel: SimplestViewModel by activityViewModels()
}


class UserFragment : Fragment(R.layout.fragment_user) {

    private val simplestViewModel: SimplestDialogFragment.SimplestViewModel by activityViewModels()

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

        simplestViewModel.userChoice.observeEvent(this) { result: Boolean ->
            // true if positive button was clicked
            Log.d(TAG, "$result")
        }
    }

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

        // show dialog with minimal params (just a message)
        showDialog<SimplestDialogFragment>(DialogArgs(R.string.dialog_message))
    }
}

Test App

The test app implements a yes/no dialog with a parameterized message to show how to pass more complex DialogArgs.