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 button = findViewById<Button>(R.id.button)
// make textview content scrollable
textView.movementMethod = ScrollingMovementMethod()
val list = mutableListOf('a','a','b','b','c','d','a',
'e','b','f','a','a','b','g','h','i')
button.setOnClickListener {
textView.text = " List: "
list.forEach { textView.append("$it, ") }
// takeWhile only returns by matching condition
// and take first elements of the list
val taken = list.takeWhile { it == 'a' }
textView.append("\n\nlist.takeWhile { it == 'a' }")
taken.forEach {
textView.append("\n$it")
}
val filtered = list.filter { it == 'a' }
textView.append("\n\nlist.filter { it == 'a' }")
filtered.forEach {
textView.append("\n$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/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="takeWhile vs filter"
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="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/button" />
</androidx.constraintlayout.widget.ConstraintLayout>

- kotlin syntax - List filter with multiple conditions
- kotlin syntax - filter list by another list
- kotlin syntax - takeIf and takeUnless
- kotlin syntax - take, takeLast, takeWhile, takeLastWhile
- kotlin syntax - List groupBy
- kotlin syntax - Distinct
- kotlin syntax - distinctBy
- kotlin syntax - getOrElse and getOrNull
- kotlin syntax - removeAll and retainAll
- kotlin syntax - plusAssign and minusAssign