Nsryjdtyk

I'm trying to learn how to implement databinding in an Android app. I have a small app I'm working with to learn this. And while I have databinding working for part of the app. I have hit a hiccup when trying to implement a recyclerview. I just cannot seem to get it. Been banging away at it for two or three days, and getting frustrated. Thought I'd ask you guys.

The app is super simple at this point.

The part i'm stuck on is accessing my recyclerview from an .xml layout from my MainFragment.kt

At first I was trying to use binding, but got frustrated and went back to just trying to use findViewById, but that is giving me issue too. I am beginning to think, I don't have as firm a grasp on databinding as I thought I did.

This is from the fragment that holds the recyclerView:

fragment_main.xml

<androidx.recyclerview.widget.RecyclerView

            android:layout_width="0dp"

            android:layout_height="0dp"

            android:layout_marginTop="8dp"

            app:layout_constraintTop_toTopOf="parent"

            app:layout_constraintStart_toStartOf="parent"

            android:layout_marginStart="8dp"

            android:layout_marginBottom="8dp"

            app:layout_constraintBottom_toBottomOf="parent"

            app:layout_constraintEnd_toEndOf="parent"

            android:layout_marginEnd="8dp"

            android:id="@+id/job_recyclerView"/>

I have another small layout file that is using Cardview to show each individual item in the recyclerview

A super simple Model:

JobData.kt

data class JobData(val companyName: String, val location: String)

An Adapter:

JobAdapter.kt

class CustomAdapter(val userList: ArrayList<JobData>) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {



//Returning view for each item in the list

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomAdapter.ViewHolder {

    val v = LayoutInflater.from(parent.context).inflate(R.layout.job_item_layout, parent, false)

    return ViewHolder(v)

}



//Binding the data on the list

override fun onBindViewHolder(holder: CustomAdapter.ViewHolder, position: Int) {

    holder.bindItems(userList[position])

}



override fun getItemCount(): Int {

    return userList.size

}



//Class holds the job list view

class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {



    fun bindItems(job: JobData) {

        val textViewName = itemView.findViewById(R.id.tv_company_name) as TextView

        val textViewAddress  = itemView.findViewById(R.id.tv_Location) as TextView

        textViewName.text = job.companyName

        textViewAddress.text = job.location

    }

}

}

And then the code in my MainFragment to handle it all, which it is not doing. I've tried everything, it was getting ugly. As you can see below. Binding is in place and working for my FloatingActionButton. But I for some reason cannot figure out how to access that recylerview. At the point the code is at below, I thought I'd just accessing using findViewById, but that is not working either.

MainFragment.kt
class MainFragment : Fragment() {

override fun onCreateView(

    inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {

    val binding: FragmentMainBinding = DataBindingUtil.inflate(

        inflater, R.layout.fragment_main, container, false)



    //Setting onClickListener for FAB(floating action button) using Navigation

    binding.createNewJobFAB.setOnClickListener { v: View ->

        v.findNavController().navigate(R.id.action_mainFragment_to_createNewJobFragment)

    }



    //getting recyclerview from xml

    val recyclerView = findViewById(R.id.job_recyclerView) as RecyclerView



    //adding a layoutmanager

    recyclerView.layoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL, false)





    //Arraylist to store jobs using the data class JobData

    val jobs = ArrayList<JobData>()



    //add dummy data to list

    jobs.add(JobData("A Company", "Town A"))

    jobs.add(JobData("B Company", "Town B"))

    jobs.add(JobData("C Company", "Town C"))

    jobs.add(JobData("D Company", "Town D"))



    //creating adapter

    val adapter = CustomAdapter(jobs)



    //add adapter to recyclerView

    recyclerView.adapter = adapter

    return binding.root

}

}

The above fails to compile for two reasons:

1. findViewById shows as an "Unresolved Reference".


2. When adding the layoutManager, "this" shows as a "Type Mismatch"

Which I believe is due to the fact that Fragments do not have a context. Or so, I think anyway. But I don't know to resolve that? Maybe override some other method, but I can't seem to figure out which or how?

Oh and MainActivity looks like:

MainActivity.kt

class MainActivity : AppCompatActivity() {



//private lateinit var binding: ActivityMainBinding



override fun onCreate(savedInstanceState: Bundle?) {

    super.onCreate(savedInstanceState)

    @Suppress("UNUSED_VARIABLE")

    val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)

}



//Ensures back button works as it should

override fun onSupportNavigateUp() = findNavController(this, R.id.navHostFragment).navigateUp()

}

Which is pointing to Nav_Graph for Android Navigation (part of JetPack). This bit is fine and working.

Adding gradle files to show that my dependencies were set correctly as suggested below.

app/gradle

android {

compileSdkVersion 28

dataBinding {

    enabled = true

}

...

}



kapt {

generateStubs = true

correctErrorTypes = true

}



dependencies {

...

kapt "com.android.databinding:compiler:$gradle_version"



...

}

Encase your xml in <layout>..<layout/>

private lateinit var binding: FragmentXXXBinding



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

        binding = FragmentXXXBinding.inflate(inflater)

        return binding.root

    }

Then you can call recyclerview by binding.jobRecyclerview

try to set all the click listeners etc on onViewCreated rather than onCreateView of fragment

It is wrong way to findViewById from Fragment(it is good technique for Activity):

val recyclerView = findViewById(R.id.job_recyclerView) as RecyclerView

First, fragment's layout have to be return by onCreateView() method.

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

  return inflater.inflate(R.layout.fragment_main, container, false)

}

I personally like do all fragment's business logic inside onViewCreated()

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

    super.onViewCreated(view, savedInstanceState)

    //Now, we can use views by kotlinx

    //val recyclerView = job_recyclerView

    //Or old-fashioned way

    val recyclerView = getView()!!.findViewById(R.id.job_recyclerView) as RecyclerView

}

RecylerView can be accessed from fragment's layout by having root view like: getView()!!.findViewById or by kotlinx inside onViewCreated(): job_recyclerView

Ok, so first of all you are getting error on findViewById bcoz your fragment is unaware about the view that contains recyclerView

What you should do is, take an instance of view that you are inflating for this fragment ( declare view as a global variable, replace your inflater line with this. )

var rootView



 // Inside onCreateView

 var rootView = inflater?.inflate(R.layout.fragment, container, false) 

Now replace, findViewById() with rootView.findViewById()

And the other error is bcoz the fragment does not have any context of it's own so replace this with activity!!

By writing activity!! you are calling getActicity() method which returns context of parent activity.