PlusAssign and minusAssign android kotlin example

Create a class MainActivity.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        btn.setOnClickListener {
            // Create a list with values
            val list = mutableListOf("RED","GREEN","BLACK","YELLOW","WHITE","BLUE")
            textView.text = "Colors:\n"
            // Iterate through the list
            list.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
        }

        btnPlusAssign.setOnClickListener {
            // Create a list with values
            val list = mutableListOf("RED","GREEN","BLACK","YELLOW","WHITE","BLUE")
            // Create another list of colors
            val listToAdd = listOf("PINK","MAGENTA","ORANGE")
            textView.text = "Elements to add:\n"
            listToAdd.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
            list.plusAssign(listToAdd)
            textView.append("\n\nAfter adding second list to first list:\n")
            list.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
        }

        btnMinusAssign.setOnClickListener {
            // Create a list with values
            val list = mutableListOf("RED","GREEN","BLACK","YELLOW","WHITE","BLUE")
            // Create another list of colors
            val listToRemove = listOf("GREEN","MAGENTA","YELLOW")
            // Iterate through the second list
            textView.text = "Elements to minus:\n"
            listToRemove.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
            // Remove the second list elements from first list
            list.minusAssign(listToRemove)
            textView.append("\n\nAfter removing second list elements from first list:\n")
            // Iterate through the first list
            list.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
        }
    }
}

Create a layout 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"
    tools:context=".MainActivity">
    <Button
        android:id="@+id/btnMinusAssign"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="minusAssign"
        app:layout_constraintStart_toEndOf="@+id/btnPlusAssign"
        app:layout_constraintTop_toTopOf="parent"
        android:textAllCaps="false" />
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginTop="8dp"
        android:text="List"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <Button
        android:id="@+id/btnPlusAssign"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="plusAssign"
        app:layout_constraintStart_toEndOf="@+id/btn"
        app:layout_constraintTop_toTopOf="parent"
        android:textAllCaps="false" />
    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:padding="16dp"
        android:text="List Example"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn"
        android:textStyle="bold" />
</androidx.constraintlayout.widget.ConstraintLayout>