android kotlin - AlertDialog multiple choice example

MainActivity.kt

package com.cfsuman.kotlintutorials

import android.os.Bundle
import android.widget.*
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import com.google.android.material.dialog.MaterialAlertDialogBuilder


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val context:MainActivity = this

        // get the widgets reference from XML layout
        val button = findViewById<Button>(R.id.button)
        val textView = findViewById<TextView>(R.id.textView)

        // initial checked items
        val initialCheckedItems =  mutableListOf<Boolean>()


        button.setOnClickListener {
            val builder = MaterialAlertDialogBuilder(context)

            // dialog title
            builder.setTitle("Select favorite colors (min 2)")

            val colors = arrayOf(
                "African violet",
                "Alice blue",
                "Alloy orange",
                "Android green",
                "Amaranth pink",
                "Antique bronze"
            )

            if (initialCheckedItems.isEmpty()){
                repeat(colors.count()) {initialCheckedItems.add(false)}
            }

            builder.setMultiChoiceItems(
                colors,
                initialCheckedItems.toBooleanArray()
            ) { dialog, which, isChecked ->}


            // alert dialog positive button
            builder.setPositiveButton("Submit"){dialog,which->
                val alertDialog = dialog as AlertDialog
                val sparseBooleanArray = alertDialog
                    .listView.checkedItemPositions
                var counter = 0

                textView.text = ""
                colors.forEachIndexed { index, s ->
                    if (sparseBooleanArray.get(index, false)) {
                        textView.append("\n$s")
                        counter += 1
                    }
                }

                if (counter > 0) {
                    textView.text = "Selected colors: " + textView.text
                }
            }


            // alert dialog neutral button
            builder.setNeutralButton("Cancel"){dialog,which->
                textView.text = ""
            }

            // set dialog non cancelable
            builder.setCancelable(false)

            // finally, create the alert dialog and show it
            val dialog = builder.create()
            dialog.show()

            // initially enable disable the positive button
            if((initialCheckedItems.filter { it }).size < 2){
                dialog.getButton(
                    AlertDialog.BUTTON_POSITIVE).isEnabled = false
            }


            // dialog list item click listener
            dialog.listView.onItemClickListener =
                AdapterView.OnItemClickListener {
                        parent, view, position, id ->
                    val sparseBooleanArray = dialog.listView
                        .checkedItemPositions
                    var checkedItems = 0
                    colors.forEachIndexed { index, s ->
                        if (sparseBooleanArray.get(index,false)){
                            checkedItems +=1
                            initialCheckedItems[index] = true
                        }else{
                            initialCheckedItems[index] = false
                        }
                    }

                    dialog.getButton(AlertDialog.BUTTON_POSITIVE)
                        .isEnabled = checkedItems >=2
                }
        }
    }
}
activity_main.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="#DCDCDC"
    android:padding="24dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Dialog"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:fontFamily="sans-serif"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/button" />

</androidx.constraintlayout.widget.ConstraintLayout>
build.gradle dependencies[add]

// Material components
implementation 'com.google.android.material:material:1.6.1'
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