Android Spinner widget doesn't show text

Question

I want to implement Spinner widget in my app. Text doesn't show in text box of Spinner. And when I selected one item, text doesn't show too.

I ran this project in my android studio. When a fragment created, a text showed in a text box of a spinner widget. And when I select a item, a selected text showed in same text box.

What's different between my project and this project. How I resolve this problem?

SleepRecordFragment.kt

import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Toast
import androidx.fragment.app.Fragment
import com.example.sleeprecorder.R
import com.example.sleeprecorder.databinding.FragmentSleepRecordBinding
import java.util.*

class SleepRecordFragment: Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding = FragmentSleepRecordBinding.inflate(inflater)

        val daysSize = 7
        val dayList = mutableListOf<String>()
        val calendar = Calendar.getInstance()

        dayList.add(
            calendar.get(Calendar.YEAR).toString() +
                    '/' +
                    calendar.get(Calendar.MONTH).toString() +
                    '/' +
                    calendar.get(Calendar.DAY_OF_MONTH).toString()
        )

        for (i in 0 ..(daysSize - 1) ) {
            calendar.add(Calendar.DAY_OF_YEAR, -1)
            Log.i("SleepRecordFragment", i.toString())
            dayList.add(
                calendar.get(Calendar.YEAR).toString() +
                        '/' +
                        calendar.get(Calendar.MONTH).toString() +
                        '/' +
                        calendar.get(Calendar.DAY_OF_MONTH).toString()
            )
        }

        val adapter = ArrayAdapter(
            this.requireContext(),
            android.R.layout.simple_spinner_item,
            dayList
        )

        binding.dateSpinner.adapter = adapter






        return binding.root
    }



}

fragment_sleep_record.xml

...
        <Spinner
            android:id="@+id/date_spinner"
            android:layout_width="413dp"
            android:layout_height="48dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="1.0"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.0" />
...

Screenshot

Answer 1

Try this

It worked for me

class SleepRecordFragment : Fragment() {

     private var _binding: FragmentSleepRecordBinding? = null

    // This property is only valid between onCreateView and
    // onDestroyView.
    private val binding get() = _binding!!
      override fun onCreateView(
            inflater: LayoutInflater,
            container: ViewGroup?,
            savedInstanceState: Bundle?
        ): View? {

            _binding = FragmentSleepRecordBinding.inflate(inflater, container, false)
            return binding.root

        }

     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
           super.onViewCreated(view, savedInstanceState)
           val daysSize = 7
           val dayList = mutableListOf<String>()
           val calendar = Calendar.getInstance()

           dayList.add(
               calendar.get(Calendar.YEAR).toString() +
                       '/' +
                       calendar.get(Calendar.MONTH).toString() +
                       '/' +
                       calendar.get(Calendar.DAY_OF_MONTH).toString()
           )

           for (i in 0 until daysSize) {
               calendar.add(Calendar.DAY_OF_YEAR, -1)
               Log.i("SleepRecordFragment", i.toString())
               dayList.add(
                   calendar.get(Calendar.YEAR).toString() +
                           '/' +
                           calendar.get(Calendar.MONTH).toString() +
                           '/' +
                           calendar.get(Calendar.DAY_OF_MONTH).toString()
               )
           }

           val adapter = activity?.let {
               ArrayAdapter(
                   it,
                   android.R.layout.simple_spinner_item,
                   dayList
               )
           }

           binding.dateSpinner.adapter = adapter
       }

       override fun onDestroyView() {
           super.onDestroyView()
           _binding = null
       }
   }