Sunday, November 3, 2019

android kotlin - removeAll and retainAll example

MainActivity.kt

package com.example.jetpack

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*

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")
            }
        }


        btnRemoveAll.setOnClickListener {
            // Create a list with values
            val list = mutableListOf("RED","GREEN","BLACK","YELLOW","WHITE","BLUE")

            // Remove elements which name stars with 'B'
            list.removeAll{ it.startsWith("B") }

            textView.text = "Remove all colors, name starts with 'B'\n"

            // Iterate through the list
            list.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
        }


        btnRetainAll.setOnClickListener {
            // Create a list with values
            val list = mutableListOf("RED","GREEN","BLACK","YELLOW","WHITE","BLUE")

            // Retain only elements with name ends with 'E'
            list.retainAll{it.endsWith("E")}

            textView.text = "Retain all colors, name ends with 'E'\n"

            // Iterate through the list
            list.forEachIndexed { index, color ->
                textView.append("\n${index+1}. $color")
            }
        }
    }
}
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/btnRetainAll"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="retainAll"
        app:layout_constraintStart_toEndOf="@+id/btnRemoveAll"
        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/btnRemoveAll"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="removeAll"
        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>