Kotlin, Coroutines, Kodein and list for RecyclerView

Question

I just started learning of Kotlin Android and I decided to use in my first Kotlin app Coroutines and Kodein library. My problem is returning list of the objects created in the Room Database. I know how to set simple list for Recyclerview, but I have problem with setting list of the objects in Recyclerview by Coroutines.

Function from activity where is using Recyclerview:

 private fun getCities() = launch(Dispatchers.Main) {
    var locationList = addLocationViewModel.location.await()
    locationList.observe(this@AddLocationActivity, Observer {

        viewAdapter = LocationAdapter(locationList, this)
    })
}

As you can see the first parameter in the LocationAdapter is locationList and this one is underlined by red color. The Error means:

Type mismatch.
 Required: kotlin.collections.ArrayList<Location>
 Found: LiveData<List<Location>>

How to resolve this?

Adapter:

class LocationAdapter(
private val cities: ArrayList<Location>,
private val context: Context
) : RecyclerView.Adapter<LocationAdapter.LocationViewHolder>() {

private var removedPosition: Int = 0
private var removedItem: String = ""


override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): LocationViewHolder {
    val layoutInflater = LayoutInflater.from(context)
    val contactRow = layoutInflater.inflate(R.layout.location_recyclerview_item, parent, false)
    return LocationViewHolder(contactRow)
}

override fun getItemCount(): Int {
    return cities.size
}

override fun onBindViewHolder(holder: LocationViewHolder, position: Int) {
    val location = holder.view.location_text_view_item

    location.text = cities.get(position).toString()
}

class LocationViewHolder(val view: View) : RecyclerView.ViewHolder(view)

fun removeItem(viewHolder: RecyclerView.ViewHolder) {
    removedItem = viewHolder.adapterPosition.toString()
    removedItem = cities[viewHolder.adapterPosition].toString()

    cities.removeAt(viewHolder.adapterPosition)
    notifyItemRemoved(viewHolder.adapterPosition)


}


}

ViewModel:

class AddLocationViewModel(
private val locationRepository: LocationRepository
) : ViewModel() {

val location by lazyDeferred {
    locationRepository.getAllLocations()
}

fun insertLocation(location: Location) {
    locationRepository
}
}

it's just location list which u have passed, make it of type Array list.seems like its List — Rohit Lalwani, Jul 26 '19 at 12:35

Ashok Kumar · Accepted Answer · 2019-07-28T12:24:31.927

2

The error itself self-explanatory , your VM is returning object of type LiveData<List<Location>>,

instead of passing the locationList(which is livedata) object directly to adapter ,create lambda like below

private fun getCities() = launch(Dispatchers.Main) {
    var locationList = addLocationViewModel.location.await()
    locationList.observe(this@AddLocationActivity, Observer { 
        locList -> viewAdapter = LocationAdapter(locList, this)
    })
}

edited Jul 28 '19 at 12:24

answered Jul 26 '19 at 12:40

Ashok Kumar

1,226
1
10
14

So how it should look like in my case? Sorry for that question, ale I'm new in Kotlin and I want to learn this in right way. – beginner992 Jul 26 '19 at 13:01
@beginner992 try updated answer, if it works for you – Ashok Kumar Jul 28 '19 at 12:25
Your solution works! I also added into the function, lines with recycler view initialising and it's fine now. Thank you so much. – beginner992 Jul 28 '19 at 13:44

score 0 · Answer 2 · answered Jul 27 '19 at 11:22

0

Just pick up the value of the LiveData object, like this:

viewAdapter = LocationAdapter(locationList.value!!, this)

answered Jul 27 '19 at 11:22

Bio-Matic

793
1
8
20

Your answer seems to be right, but I have problem with Recyclerview initialization. When I'm going to activity with Recycylerview the app crashes and I see this: lateinit property viewAdapter has not been initialized. I'm trying to find answer, but still nothing. – beginner992 Jul 27 '19 at 13:56

Kotlin, Coroutines, Kodein and list for RecyclerView

2 Answers2