Sunday, October 20, 2019

android kotlin - takeIf and takeUnless 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)

        val list = generateList()

        btn.setOnClickListener {
            textView.text = "Employees:\n"
            // Iterate through the list
            list.forEach {
                textView.append("\n${it.name} : age ${it.age} : salary $${it.salary}")
            }
        }

        btnTakeIf.setOnClickListener {
            textView.text = "Take if list is not empty:\n"
            list.takeIf {
                it.isNotEmpty() // required boolean
            }.apply {
                this?.forEach {
                    // do the task
                    textView.append("\n" + it.name)
                }
            }
        }

        btnTakeUnless.setOnClickListener {
            textView.text = "Take unless list is empty:\n"
            list.takeUnless {
                it.isEmpty()// required boolean
            }.apply {
                this?.forEach {
                    // do the task
                    textView.append("\n" + it.name)
                }
            }
        }
    }
}


// Method to generate employee list
private fun generateList():MutableList<Employee>{
    val list = mutableListOf<Employee>()
    list.add(Employee("Weston",25,6500))
    list.add(Employee("Gregg",29,5400))
    list.add(Employee("Erika",24,5200))
    list.add(Employee("Ashly",19,4900))
    list.add(Employee("Tristian",20,2600))
    list.add(Employee("Violette",23,4650))
    list.add(Employee("Viviane",37,5100))
    list.add(Employee("Kyra",48,4100))
    list.add(Employee("Uriel",19,2300))
    list.add(Employee("Isaias",16,6800))
    return list
}

// Data class for Employee
data class Employee(
    val name:String,
    val age:Int,
    val salary:Int
)
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/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Employees"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <Button
        android:id="@+id/btnTakeIf"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Take If"
        app:layout_constraintStart_toEndOf="@+id/btnTakeUnless"
        app:layout_constraintTop_toTopOf="parent" />
    <Button
        android:id="@+id/btnTakeUnless"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Take Unless"
        app:layout_constraintStart_toEndOf="@+id/btn"
        app:layout_constraintTop_toTopOf="parent" />
    <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" />
</androidx.constraintlayout.widget.ConstraintLayout>
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