Sunday, October 27, 2019

android kotlin - maxBy and maxWith 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)

        // Create a list with values
        val list = generateList()

        btn.setOnClickListener {
            textView.text = "Employees:\n"

            // Iterate through the list
            list.forEachIndexed { index, emp ->
                textView.append("\n${index+1}. ${emp.name} : ")
                textView.append("${emp.age} : $${emp.salary}")
            }
        }


        btnMaxBy.setOnClickListener {
            // Get the oldest employee from this list
            val maxAge:Employee? = list.maxBy { it.age }

            textView.text = "Employee max by age:\n"
            maxAge?.apply {
                textView.append("\n${this.name} : ${this.age} : ${this.salary}")
            }
        }


        btnMaxWith.setOnClickListener {
            // Get the employee from this list whose name length is biggest
            val maxLengthName:Employee? = list.maxWith(
                Comparator { emp1, emp2 ->
                    emp1.name.length - emp2.name.length
                }
            )

            textView.text = "Employee max with name length:\n"
            maxLengthName?.apply {
                textView.append("\n${this.name} : ${this.age} : ${this.salary}")
            }
        }
    }
}


// Method to generate employee list
private fun generateList():MutableList<Employee>{
    val list = mutableListOf<Employee>()
    list.add(Employee("Elian",24,6500))
    list.add(Employee("Gregg",29,5400))
    list.add(Employee("Brisa",24,5200))
    list.add(Employee("Clementine",19,4900))
    list.add(Employee("Lauriane",25,2300))
    list.add(Employee("Amy",25,2000))
    list.add(Employee("Tristian",54,5100))
    list.add(Employee("Frederic",20,2600))
    list.add(Employee("Innee",25,4100))
    list.add(Employee("Sabryna",54,5100))
    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/btnMaxWith"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="maxWith"
        app:layout_constraintStart_toEndOf="@+id/btnMaxBy"
        app:layout_constraintTop_toTopOf="parent" />
    <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="List"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <Button
        android:id="@+id/btnMaxBy"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="maxBy"
        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"
        android:textStyle="bold" />
</androidx.constraintlayout.widget.ConstraintLayout>