Material Toggle Button SharedPreferences

Question

I have a MaterialButtonToggleGroup inside an alert dialog with 2 buttons that looks like: Toggle

I am having trouble getting sharedPreferences to work so that the user's choice is still selected when they return to the dialog.

    <com.google.android.material.button.MaterialButtonToggleGroup
       android:id="@+id/toggleButton"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       app:singleSelection="true"
       app:selectionRequired="true"
       android:layout_gravity="center"
       android:layout_marginBottom="50dp"
       app:checkedButton="@+id/on">
    <Button
        style="?attr/materialButtonOutlinedStyle"
        android:id="@+id/on"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/black"
        app:cornerRadius="15dp"
        android:textSize="20sp"
        android:text="@string/on" />
    <Button
        style="?attr/materialButtonOutlinedStyle"
        android:id="@+id/off"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:cornerRadius="15dp"
        android:textColor="@color/black"
        android:textSize="20sp"
        android:text="@string/off" />
</com.google.android.material.button.MaterialButtonToggleGroup>    

               




view.toggleButton?.addOnButtonCheckedListener { toggleButton, checkedId, isChecked ->
            if (!isChecked) return@addOnButtonCheckedListener
               if (checkedId == R.id.on) {
                       //do something
           }

           if (checkedId == R.id.off) {
                     //do something
          }
       } 



    private fun retrieveData() {
         // what goes here?
    }   

    override fun onResume() {
        super.onResume()
        retrieveData()
    }

Answer 1

First you need to declare the SharedPreferences, initialize it and then saving its value on the user action and retrieve the value when the fragment is initialized (onViewCreated), here's the snippet:

class FragmentB : Fragment() {
    private lateinit var sharedPreferences: SharedPreferences

    ...

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

        sharedPreferences = requireActivity().getSharedPreferences("MyPrefs", Context.MODE_PRIVATE)

        val toggleButton = view.findViewById<MaterialButtonToggleGroup>(R.id.toggleButton)
        toggleButton?.addOnButtonCheckedListener { toggleButton, checkedId, isChecked ->
            if (!isChecked) return@addOnButtonCheckedListener
            if (checkedId == R.id.on) {
                // save selected option ON as true
                sharedPreferences.edit().putBoolean("option", true).apply()
            }

            if (checkedId == R.id.off) {
                // save selected option OFF as false
                sharedPreferences.edit().putBoolean("option", false).apply()
            }
        }

        retrieveData()
    }

    private fun retrieveData() {
        view?.findViewById<MaterialButtonToggleGroup>(R.id.toggleButton)?.let {
            // get saved options being default as false
            val option = sharedPreferences.getBoolean("option", false)
            if (option) {
                it.check(R.id.on)
            } else {
                it.check(R.id.off)
            }
        }
    }
}