android kotlin - Difference between takeWhile and filter

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>

More android examples