Android kotlin: How to implement if else statement

Android Kotlin - Understanding if else statements

This code demonstrates various ways to implement conditional logic using if statements in Kotlin for an Android application. The code utilizes buttons to trigger different functionalities related to finding the largest number among predefined variables. The TextView element displays the results.

The code explores four approaches:

1. Traditional if statement
2. if with else statement
3. if else if statement
4. if as expression

Each button click triggers a specific code block that calculates the biggest number between two variables (a and b) or three variables (a, b, and c) and displays the result on the TextView.

Summary

By understanding these different if statement implementations, developers can choose the most appropriate approach for their specific needs. For simple conditions, a single if statement might suffice. However, for more complex scenarios with multiple possibilities, if else if statements provide a structured way to handle different conditions. Additionally, Kotlin allows for concise if-else logic within a single line using an if expression. This code example provides a practical demonstration of these concepts for Android development using Kotlin.

MainActivity.kt

package com.cfsuman.kotlinexamples

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView


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.text_view)
        val button = findViewById<Button>(R.id.button);
        val button2 = findViewById<Button>(R.id.button2);
        val button3 = findViewById<Button>(R.id.button3);
        val button4 = findViewById<Button>(R.id.button4);

        // Initialize some integer type variables
        var a:Int = 5
        var b:Int = 10
        var c:Int = 8

        // Traditional if statement
        button.setOnClickListener{
            var max = a

            if(a < b) max = b
            textView.text = "From $a and $b, biggest number is $max"
        }


        // If with else statement
        button2.setOnClickListener{
            var max:Int

            if(a > b){
                max = a
                textView.text = "$max is biggest number in $a and $b"
            }else{
                max = b
                textView.text = "$max is biggest number in $a and $b"
            }
        }


        // If else if statement
        button3.setOnClickListener{
            var max:Int

            if(a > b && a > c){
                max = a
                textView.text = "$max is biggest number from $a and $b and $c"
            }else if (b > a && b > c){
                max = b
                textView.text = "$max is biggest number from $a and $b and $c"
            }else{
                max = c
                textView.text = "$max is biggest number from $a and $b and $c"
            }
        }


        // If as expression
        button4.setOnClickListener{
            // If else in one line
            var max = if(a > b) a else b
            textView.text = "$max is biggest number from $a and $b"
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    >
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="If Statement"
        />
    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="If Else Statement"
        />
    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="If Else If Statement"
        />
    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="If As Expression"
        />
    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="23sp"
        android:textStyle="bold"
        android:textColor="#ff191d"
        android:layout_marginTop="20dp"
        />
</LinearLayout>