How to write the adapter class for the following recycler view? - kotlin

Question

I am trying to make a Todo app and I have done the Room part and able to store data now I want to display the data in the form of Recycler View but I am not getting how to write the adapter class corresponding to it. I looked for it in different sites I never got any satisfying answer.
**TodoFragViewModel.kt""
class TodofragViewModel(
val database: TodoDao, applicaltion: Application
): AndroidViewModel(applicaltion) {
// TODO: Implement the ViewModel
/**
* viewModelJob allows us to cancel all coroutines started by this ViewModel.
*/
private var viewModelJob = Job()
/**All coroutines can be cancelled by viewmodelJob.cancel() and Dispatcher.main is byDefault choice
*/
private val uiScope = CoroutineScope(Dispatchers.Main + viewModelJob)
private val currenctTodo = MutableLiveData<Todo?>()
private val allTodo = database.getAllTodo()
init{
intializeThisTodo()
}
private fun intializeThisTodo(){
uiScope.launch {
currenctTodo.value=getFromDatabase()
}
}
private suspend fun getFromDatabase(): Todo? {
return withContext(Dispatchers.IO){
val info =database.getCurrentTodo()
info
}
}
private suspend fun insert(thisTodo: Todo) {
withContext(Dispatchers.IO) {
database.insert(thisTodo)
Log.i("Database","${database.getCurrentTodo()?.description} and ${database.getCurrentTodo()?.time}")
}
}
fun onAdded(time:String,description:String) {
uiScope.launch {
val thisTodo = Todo(time,description)
insert(thisTodo)
currenctTodo.value=getFromDatabase()
}
}
/**
* Called when the ViewModel is dismantled.
* At this point, we want to cancel all coroutines;
* otherwise we end up with processes that have nowhere to return to
* using memory and resources.
*/
override fun onCleared() {
super.onCleared()
viewModelJob.cancel()
}
}
todo_recycler_view
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="wrap_content">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/date_text"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/todo_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/date_text" />
</androidx.constraintlayout.widget.ConstraintLayout>
TodoFrag.kt
class todofrag : Fragment() {
companion object {
fun newInstance() = todofrag()
}
private lateinit var viewModel: TodofragViewModel
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.todofrag_fragment, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
val application = requireNotNull(this.activity).application
val dataSource= TodoDatabase.getInstance(application)?.InformationDatabaseDao
val viewModelFactory = dataSource?.let { TodoViewModelFactory(it, application) }
val viewModel=ViewModelProviders.of(this,viewModelFactory).get(TodofragViewModel::class.java)
add_button.setOnClickListener{
val currentDate: String = SimpleDateFormat("dd/MM/yyyy", Locale.getDefault()).format(Date())
val currentTime: String = SimpleDateFormat("HH:mm:ss", Locale.getDefault()).format(Date())
val time:String="${currentDate} \n ${currentTime}"
viewModel.onAdded(time,todo_text.text.toString())
}
}
}
Please let me know if any other files are added. By the way, I tried to use card view so that it looked good.

Answer 1

The developer documentation explains it pretty well.
This might not be perfectly suited for what you need, but it should be a good start. Specifically, I don't know all the fields for your Todo class, so make sure you account for those in this code.
Basically, you'll want to have a ViewHolder that represents your CardView
class TodoViewHolder(convertView: View) : RecyclerView.ViewHolder(convertView) {
val dateText = convertView.findViewById(R.id.date_text)
val description = convertView.findViewById(R.id.todo_description)
// whatever else you need access to
}
And you'll want to use DiffUtil for a better user experience. This allows for some animations when things in the list change, such as removing an item, editing an item, or adding an item.
private class TodoDiffCallback : DiffUtil.ItemCallback<Todo>() {
override fun areItemsTheSame(oldItem: Todo, newItem: Todo) =
oldItem.id == newItem.id
override fun areContentsTheSame(oldItem: Todo, newItem: Todo) =
oldItem.dateText == newItem.dateText && oldItem.description == newItem.description
}
You'll want to extend ListAdapter and override its methods. onCreateViewHolder creates an instance of your TodoViewHolder for each view that is seen and onBindViewHolder allows you to add behavior to each item in the list. It is worth noting that you can pass parameter into the adapter in case you need to.
class MyListAdapter : ListAdapter<Todo, TodoViewHolder>(TodoDiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = TodoViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.todo_recycler_view, parent, false))
override fun onBindViewHolder(holder: TodoViewHolder, position: Int) {
val todo = getItem(position)
holder.dateText = todo.dateText
holder.description = todo.description
// add whatever click listener and other stuff you need
}
}
In your fragment, when you access your RecyclerView, just add an instance of the adapter if it's null.
if (recyclerView.adapter == null) {
recyclerView.adapter = TotoListAdapter()
}
And when you want to add data (that you have retrieved from Room or your API) to the adapter (in the fragment/activity), just do the following:
(recyclerView.adapter as? TodoListAdapter)?.submitList(data)
On a side note, make sure to clean up your style (you can use the Reformat Code command in the Code menu), and you would want to rename the todo_recycler_view to something like todo_view. You'll want to have a RecyclerView layout in your fragment layout.