Spinner, AutoComplete & Date/Time Pickers

<Spinner
    android:id="@+id/spClass"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

<!-- res/values/arrays.xml -->
<string-array name="classes">
    <item>Class 9</item>
    <item>Class 10</item>
    <item>Class 11</item>
    <item>Class 12</item>
</string-array>

val classes = resources.getStringArray(R.array.classes)
val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, classes)
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
binding.spClass.adapter = adapter

binding.spClass.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
    override fun onItemSelected(parent: AdapterView<*>, view: View?, position: Int, id: Long) {
        Log.d("Form", "Selected ${classes[position]}")
    }
    override fun onNothingSelected(parent: AdapterView<*>) {}
}
val selected = binding.spClass.selectedItem as String

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/tilSubject"
    style="@style/Widget.Material3.TextInputLayout.OutlinedBox.ExposedDropdownMenu"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Subject">

    <com.google.android.material.textfield.MaterialAutoCompleteTextView
        android:id="@+id/actvSubject"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="none" />
</com.google.android.material.textfield.TextInputLayout>

// Kotlin
val subjects = listOf("Maths", "Physics", "Chemistry", "Biology", "English")
binding.actvSubject.setAdapter(ArrayAdapter(this, android.R.layout.simple_list_item_1, subjects))
binding.actvSubject.setText(subjects.first(), false)        // false = do not filter
binding.actvSubject.setOnItemClickListener { _, _, position, _ ->
    Toast.makeText(this, subjects[position], Toast.LENGTH_SHORT).show()
}

<AutoCompleteTextView
    android:id="@+id/actvCity"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:completionThreshold="1"
    android:hint="City" />

// Kotlin – suggestions appear after typing 1 letter
val cities = arrayOf("Agra", "Aligarh", "Allahabad", "Delhi", "Dehradun", "Lucknow")
binding.actvCity.setAdapter(ArrayAdapter(this, android.R.layout.simple_list_item_1, cities))

import com.google.android.material.datepicker.CalendarConstraints
import com.google.android.material.datepicker.DateValidatorPointForward
import com.google.android.material.datepicker.MaterialDatePicker
import java.text.SimpleDateFormat
import java.util.Date
import java.util.Locale
import java.util.TimeZone

binding.btnDate.setOnClickListener {
    val constraints = CalendarConstraints.Builder()
        .setValidator(DateValidatorPointForward.now())       // no past dates
        .build()
    val picker = MaterialDatePicker.Builder.datePicker()
        .setTitleText("Exam date")
        .setSelection(MaterialDatePicker.todayInUtcMilliseconds())
        .setCalendarConstraints(constraints)
        .build()
    picker.addOnPositiveButtonClickListener { utcMillis ->
        val fmt = SimpleDateFormat("dd MMM yyyy", Locale.getDefault())
        fmt.timeZone = TimeZone.getTimeZone("UTC")            // the selection is UTC midnight
        binding.btnDate.text = fmt.format(Date(utcMillis))
    }
    picker.show(supportFragmentManager, "date")
}

import com.google.android.material.timepicker.MaterialTimePicker
import com.google.android.material.timepicker.TimeFormat

binding.btnTime.setOnClickListener {
    val picker = MaterialTimePicker.Builder()
        .setTimeFormat(TimeFormat.CLOCK_12H)
        .setHour(9)
        .setMinute(30)
        .setTitleText("Class time")
        .build()
    picker.addOnPositiveButtonClickListener {
        val h = picker.hour
        val m = picker.minute
        val amPm = if (h < 12) "AM" else "PM"
        val h12 = if (h % 12 == 0) 12 else h % 12
        binding.btnTime.text = String.format(Locale.getDefault(), "%d:%02d %s", h12, m, amPm)
    }
    picker.show(supportFragmentManager, "time")
}

// From Student Diary – AddEditNoteFragment.pickDateTime()
datePicker.addOnPositiveButtonClickListener { utcMillis ->
    val utc = Calendar.getInstance(TimeZone.getTimeZone("UTC")).apply { timeInMillis = utcMillis }
    val timePicker = MaterialTimePicker.Builder().setTimeFormat(TimeFormat.CLOCK_12H).setHour(9).build()
    timePicker.addOnPositiveButtonClickListener {
        val local = Calendar.getInstance().apply {
            set(utc.get(Calendar.YEAR), utc.get(Calendar.MONTH), utc.get(Calendar.DAY_OF_MONTH),
                timePicker.hour, timePicker.minute, 0)
        }
        dueAt = local.timeInMillis              // used to schedule the reminder
    }
    timePicker.show(childFragmentManager, "time")
}