android kotlin - take, takeLast, takeWhile, takeLastWhile example

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 btnTake = findViewById<Button>(R.id.btnTake)
        val btnTakeWhile = findViewById<Button>(R.id.btnTakeWhile)
        val btnTakeLastWhile = findViewById<Button>(
            R.id.btnTakeLastWhile)


        // make textview content scrollable
        textView.movementMethod = ScrollingMovementMethod()


        val list = mutableListOf('a','a','b','b','c','d','a',
            'e','e','f','a','a','g','g','h','i')


        btnTake.setOnClickListener {
            textView.text = " List: "
            list.forEach { textView.append("$it, ") }

            val taken = list.take(5)
            textView.append("\n\n list.take(5)\n")

            taken.forEach {
                textView.append("$it, ")
            }


            val takenLast = list.takeLast(4)
            textView.append("\n\n list.takeLast(4)\n")

            takenLast.forEach {
                textView.append("$it, ")
            }
        }


        btnTakeWhile.setOnClickListener {
            textView.text = " List: "
            list.forEach { textView.append("$it, ") }

            val taken = list.takeWhile { it == 'a' }
            textView.append("\n\n list.takeWhile { it == 'a' }\n")

            taken.forEach {
                textView.append("$it, ")
            }
        }


        btnTakeLastWhile.setOnClickListener {
            textView.text = " List: "
            list.forEach { textView.append("$it, ") }

            val taken = list.takeLastWhile { it > 'e' }
            textView.append("\n\n list.takeLastWhile " +
                    "{ it > 'e' }\n")

            taken.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/btnTake"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="take"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnTakeWhile"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:text="takeWhile"
        android:textAllCaps="false"
        app:layout_constraintBottom_toBottomOf="@+id/btnTake"
        app:layout_constraintStart_toEndOf="@+id/btnTake" />

    <Button
        android:id="@+id/btnTakeLastWhile"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:text="takeLastWhile"
        android:textAllCaps="false"
        app:layout_constraintBottom_toBottomOf="@+id/btnTakeWhile"
        app:layout_constraintStart_toEndOf="@+id/btnTakeWhile" />

    <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/btnTake" />

</androidx.constraintlayout.widget.ConstraintLayout>

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