MainActivity.kt
package com.cfsuman.kotlintutorials
import android.os.Bundle
import android.text.method.ScrollingMovementMethod
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// get the widgets reference from XML layout
val textView = findViewById<TextView>(R.id.textView)
val btnList = findViewById<Button>(R.id.btnList)
val btnGroupBy = findViewById<Button>(R.id.btnGroupBy)
// make textview content scrollable
textView.movementMethod = ScrollingMovementMethod()
// Create a list with values
val list = listOf("RED","GREEN","YELLOW","MAGENTA",
"PINK","WHITE","BLACK","BLUE",
"SALMON","MAROON","PURPLE")
btnList.setOnClickListener {
textView.text = "List:\n"
// Iterate through the list
list.forEach {
textView.append("\n$it")
}
}
btnGroupBy.setOnClickListener {
// Groups the colors by it length
val groups:Map<Int,List<String>> = list.groupBy {
it.length
}
textView.text = ""
groups.forEach{
val length = it.key
val colors = it.value
textView.append("\n\n${colors.size} Color(s)" +
" length is $length : ")
colors.forEach {
textView.append("$it, ")
}
}
}
}
}
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="#F8F8F8"
android:padding="24dp">
<Button
android:id="@+id/btnList"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="List"
android:textAllCaps="false"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/btnGroupBy"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="12dp"
android:text="groupBy"
android:textAllCaps="false"
app:layout_constraintBottom_toBottomOf="@+id/btnList"
app:layout_constraintStart_toEndOf="@+id/btnList" />
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginTop="16dp"
android:fontFamily="sans-serif"
android:textSize="24sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/btnList" />
</androidx.constraintlayout.widget.ConstraintLayout>
