Android: Enable a Button inside RecyclerView.ViewHolder

Question

I have a button (id: readyButtonIntro) inside a layout (introscreen.xml) that i need to enable. To do that, i have another button inside the RecyclerView.ViewHolder.

This is my Layout to need access

introscreen.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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="match_parent"
    android:background="@color/colorWhite"
    tools:context=".IntroScreenVC">


    <LinearLayout
        android:id="@+id/indicatorContainer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="40dp"
        android:gravity="center"
        android:orientation="horizontal"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/readyButtonIntro"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        android:background="@color/colorWhite"
        android:textColor="@color/colorTerciary"
        android:alpha="0"
        android:enabled="false"
        android:text="Ready"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

And the another button is inside into the ViewHolder

slide_item_container.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="15dp"
    >

    <Button
        android:id="@+id/addData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:text="Agregar Datos"
        android:background="@drawable/button_rounded2"
        />

</LinearLayout>

How can I enable from inside the class that listener the button?

class IntroSlideViewHolder(view: View) : RecyclerView.ViewHolder(view) {

    init {
        addData.setOnClickListener(View.OnClickListener {

        //NEED TO ENABLE THE BUTTON
        // val introScreen = IntroScreenVC()
        // introScreen.readyButton()

    }
}

I have a fun into IntroScreenVC but always have a error that its null, if a pass the context or view, do nothing.

     fun readyButton(){

         readyButtonIntro.isEnabled = true
      }

Could you help me with this? I would really appreciate it. Thank you very much! Regards.

---

Edit:

I put the adapter and the ViewHolder for more information. I ignored that because I didn't want to create confusion. Sorry for that..

Class Constructor

data class IntroSlide(val title: String, val description: String, val icon: Int, val firstButton: Boolean, val secondButton: Boolean, val thirdButton: Boolean)

IntroScreenVC.kt

class IntroScreenVC: AppCompatActivity() {

    private val introSliderAdapter = IntroScreenAdapter(
        listOf(
            IntroSlide(
                "title1",
            "description1",
                R.drawable.logo,
                false,
                false,
                false
            ),
            IntroSlide(
                "title2",
                "description2",
                R.drawable.doggrooming,
            true,
                false,
                false
            ),
            IntroSlide(
                "title3",
                "description3",
                R.drawable.introscreen3,
                false,
                true,
                false
            )
        )
    )

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.introscreen)

        introSliderViewPager.adapter = introSliderAdapter
    }
}

IntroScreenAdapter.kt

class IntroScreenAdapter(private val introSlides: List<IntroSlide>) : RecyclerView.Adapter<IntroSlideViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): IntroSlideViewHolder {

        val layoutInflater = LayoutInflater.from(parent?.context)
        val cellForRow = layoutInflater.inflate(R.layout.slide_item_container,parent,false)
        return IntroSlideViewHolder(cellForRow)
    }

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

    override fun onBindViewHolder(holder: IntroSlideViewHolder, position: Int) {
        holder.bind(introSlides[position])

    }

}

class IntroSlideViewHolder(view: View) : RecyclerView.ViewHolder(view) {

    private val textTitle = view.findViewById<TextView>(R.id.textTitle)
    private val textDescription = view.findViewById<TextView>(R.id.textDescription)
    private val imageIcon = view.findViewById<ImageView>(R.id.imageSlideIcon)
    private val addData = view.findViewById<Button>(R.id.addData)
    private val addPet = view.findViewById<Button>(R.id.agregarMascota)

    val contexto = itemView.context;

    fun bind(introSlide: IntroSlide) {
        textTitle.text = introSlide.title
        textDescription.text = introSlide.description
        imageIcon.setImageResource(introSlide.icon)
        addData.isEnabled = introSlide.firstButton
        addPet.isEnabled = introSlide.thirdButton
        }
    }



    init {
        addData.setOnClickListener(View.OnClickListener {

           //ADD A ALERTDIALOG AND WHEN PRESS OK NEED TO ENABLE THAT BUTTON
            val mDialogView =  LayoutInflater.from(contexto).inflate(R.layout.alertdialog_add_data,null)
            val builder = AlertDialog.Builder(contexto)
            builder.setView(mDialogView)
            val dialog: AlertDialog = builder.create()
            dialog.show()
            dialog.getWindow()?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT));
            mDialogView.agregarDatosOK.setOnClickListener {
            //HERE I NEED TO ENABLE THE BUTTON 
            //readyButtonIntro(introscreen.xml)
            }
          }
}

---

Edit2:

This is what I do with sharedPreferences.

IntroScreenAdapter.kt

class IntroSlideViewHolder(view: View) : RecyclerView.ViewHolder(view) {

    private val textTitle = view.findViewById<TextView>(R.id.textTitle)
    private val textDescription = view.findViewById<TextView>(R.id.textDescription)
    private val imageIcon = view.findViewById<ImageView>(R.id.imageSlideIcon)
    private val addData = view.findViewById<Button>(R.id.addData)
    private val addPet = view.findViewById<Button>(R.id.agregarMascota)

//INIT sharedPreferences
private val prefs: SharedPreferences = view.context.getSharedPreferences(getString(R.string.prefs_file), Context.MODE_PRIVATE)

    val contexto = itemView.context;

    fun bind(introSlide: IntroSlide) {
        textTitle.text = introSlide.title
        textDescription.text = introSlide.description
        imageIcon.setImageResource(introSlide.icon)
        addData.isEnabled = introSlide.firstButton
        addPet.isEnabled = introSlide.thirdButton
        }
    }



    init {
        addData.setOnClickListener(View.OnClickListener {
            val mDialogView = LayoutInflater.from(contexto).inflate(R.layout.alertdialog_add_data,null)
            val builder = AlertDialog.Builder(contexto)
            builder.setView(mDialogView)
            val dialog: AlertDialog = builder.create()
            dialog.show()
            dialog.getWindow()?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT));
            mDialogView.agregarDatosOK.setOnClickListener {


                    //HERE EDIT THE sharedPreferences
                    with (prefs.edit()) {
                        putBoolean("ready_button_enabled", true)
                        apply()
                    }

                    dialog.dismiss()

            }
          }
}

IntroScreenVC.kt

class IntroScreenVC: AppCompatActivity() {

    private val introSliderAdapter = IntroScreenAdapter(
        listOf(
            IntroSlide(
                "title1",
            "description1",
                R.drawable.logo,
                false,
                false,
                false
            ),
            IntroSlide(
                "title2",
                "description2",
                R.drawable.doggrooming,
            true,
                false,
                false
            ),
            IntroSlide(
                "title3",
                "description3",
                R.drawable.introscreen3,
                false,
                true,
                false
            )
        )
    )

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.introscreen)

        introSliderViewPager.adapter = introSliderAdapter
    }


    //HERE PUT THE RESUME TO EXPECT THE SHOW AND ENABLE THE BUTTON

    override fun onResume() {
        super.onResume()

        val prefs = getSharedPreferences(getString(R.string.prefs_file), Context.MODE_PRIVATE)
        val buttonEnabled = prefs.getBoolean("ready_button_enabled", false)
        readyButtonIntro.isEnabled = buttonEnabled
        if (buttonEnabled) {
            readyButtonIntro.alpha = 1f
        }else {
            readyButtonIntro.alpha = 0f

        }

    }
}

---

SOLUTION:

Into the Activity (IntroScreenVC)

class IntroScreenVC: AppCompatActivity(), IntroScreenAdapter.AdapterOnClick {

    private val introSliderAdapter =
        listOf(
           ...
        )

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.introscreen)

        introSliderViewPager.adapter = IntroScreenAdapter(introSliderAdapter, this)
}

...

    override fun onClick() {
        //HERE ENABLE AND SHOW THE BUTTON
        readyButtonIntro.isEnabled = true
        readyButtonIntro.alpha = 1f

    }

And the into the Adapter and RecyclerView

class IntroScreenAdapter(private val introSlides: List<IntroSlide>, val adapterOnClick: AdapterOnClick) : RecyclerView.Adapter<IntroScreenAdapter.IntroSliderViewHolder>() {


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): IntroScreenAdapter.IntroSliderViewHolder {

        val layoutInflater = LayoutInflater.from(parent?.context)
        val cellForRow = layoutInflater.inflate(R.layout.slide_item_container,parent,false)
        return IntroSliderViewHolder(cellForRow)
    }

...

inner class IntroSliderViewHolder(view: View) : RecyclerView.ViewHolder(view) {

...

init {
            addData.setOnClickListener(View.OnClickListener {
                val mDialogView = LayoutInflater.from(contexto).inflate(R.layout.alertdialog_add_data,null)
                val builder = AlertDialog.Builder(contexto)
                builder.setView(mDialogView)
                val dialog: AlertDialog = builder.create()
                dialog.show()
                dialog.getWindow()?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT));
                mDialogView.agregarDatosOK.setOnClickListener {

                        //FINALLY HERE CHANGE THE BUTTON TO ENABLE :)
                 adapterOnClick.onClick()

}
}
}
}

Answer 1

As I understand your problem you have a class A that is trying to communicate (change something) in class B. There are several options for solving this kind of problem, depending on your exact needs.

From the code you have provided the relation of your Layouts and classes is not clear enough to me to give a more precise answer. First of all, I understand you are using a recycler view. A recycler view can have many items, and I assume you want to be able to enable that button from each item.

In order to let your IntroScreen class communicate with your viewholder, you have to pass a reference to the ViewHolder constructor.

For this purpose you could implement a simple "callback pattern". Here is an example for defining an interface (e.g. for a function that enables the button) and implementing the callback. Have a read here to see a well-explained example in Java. In Kotlin you could do it the same way.

Here a summary of the implementation steps:

1. define interface EnableButtonCallback that implements an abstract method enableButton
2. let your InfoScreen class implement that interface (in which you enable the button)
3. pass your InfoScreen class to your RecyclerView adapter and then from your adapter to your ViewHolder
4. in your ViewHolder onClickListener call the interface method enableButton

Update 2020/08/11

I try to give suggestions based on your updated code. In the intro screen you set your viewPager adapter, but it is still not clear where this property is coming from and where exactly it is displayed. I guess maybe you just cut out the parameter definition. However, I just assume you have your views set up properly and this is not a problem here. For using recycler view with viewPager I found some related information here.

I can not yet see your use case clearly yet. Are you adding data persistently? Then should your button in the IntroScreen be permanently enabled? In this case probably SharedPreferences are a good choice for persisting this kind of information. Even when it doesn't need to be persisted. Reading one shared preference file is lightweight and quick enough to be done on the main thread. I will give you an example implementation here:

1. Get a shared preferences object

    val sharedPref = activity?.getSharedPreferences(
        "intro_button_settings_file", Context.MODE_PRIVATE) // String with the key should be in your string resource file

2. Pass your sharedPref to your adapter and your viewHolder and write to it:

    with (sharedPref.edit()) {
        putBoolean("ready_button_enabled", true) // String with the key should be in your string resource file
        commit()
    }

3. in your IntroScreen check the setting

    val readyButtonShouldBeEnabled = sharedPref.getBoolean("ready_button_enabled", 
        false) // defaults to false

If, after clicking your enable button (that sets the setting to true), you need to return to your IntroScreen activity: then you could enable your button in your activities onResume method A different solution would be: You check the setting in your IntroScreen onClick method. Then you don't need to disable the button. You just set:

// in your IntroScreen readyButtonIntro onClick method
val buttonEnabled = sharedPref.getBoolean("ready_button_enabled", 
        false)
if (!buttonEnabled) {
    // optional: write a Toast to notify the user why the button is doing nothing (yet)
    Toast.makeText(yourIntroScreenContext, "First agregar datos", Toast.LENGTH_SHORT).show()
    return // onClick returns, so nothing else will happen when clicked
}
... // your code when the button **should** be enabled

If your button should be disabled again, simply save false to the setting.

Since I do not know more about your use case, this seems like an easy and quick solution to me. This way you do not need to bother with implementing an interface. Anyways, when clicking your button in your viewHolder there is no immediate action taking place in your IntroScreen activity. You still want the user to return to the IntroScreen and click the enabled button. Then checking if your button was enabled just when clicking on it appears sufficient to me.