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Kotlin Articles
Page 10 of 21
What is the difference between "const" and "val" in Kotlin?
const KeywordThe const keyword is used in Kotlin whenever the variable value remains const throughout the lifecycle of an application. It means that const is applied only on immutable properties of the class. In simple words, use const to declare a read-only property of a class.There are some constraints that are applied to the const variable. They are as follows −const can only be applied to the immutable property of a class.It cannot be assigned to any function or any class constructor. It should be assigned with a primitive data type or String.The const variable will be initialized at compile-time.ExampleIn ...
Read MoreKotlin – Property initialization using "by lazy" vs. "lateinit
Kotlin library provides two different access modifiers for property declaration.In this article, we will highlight the difference between these two access modifiers and how we can use them in our application.LateinitIn order to create a "lateInit" variable, we just need to add the keyword "lateInit" as an access modifier of that variable. Following are a set of conditions that need to be followed in order to use "lateInit" in Kotlin.Use "lateInit" with a mutable variable. That means, we need to use "var" keyword with "lateInit"."lateInit" is allowed only with non-NULLable data types."lateInit" does not work with primitive data types."lateInit" can ...
Read MoreHow to check if a "lateInit" variable has been initialized in Kotlin?
Any variable which is initialized after its declaration is known as a "late initialized variable". In conventional programming languages, any non-NULL type of variable need to be initialized in the constructor. But sometimes, by mistake, developers forget to do these NULL checks which causes a programming error. In order to avoid this situation, Kotlin introduced a new modifier called as "lateInit". Along with this modifier, Kotlin provides a couple of methods to check whether this variable is initialized or not.In order to create a "lateInit" variable, we just need to add the keyword "lateInit" as an access modifier of that ...
Read MoreWhat is the equivalent of Java static methods in Kotlin?
In Java, "static" keyword is used for efficient memory management. Once a variable or method is declared as static, then the JVM will allocate memory for these variable only once. Usually static variables are used to declare common properties of a class, for example, "Name of the institution". In the following example, we will see how to use the static keyword.Example of Static in using JavaIn order to demonstrate how static works in Java, we will access our online Java compiler and we will create a Test class. Inside Test, we will try to create a static variable along with ...
Read MoreHow to iterate over a Hashmap in Kotlin?
A Map is a collection where data is stored as a key-value pair and the corresponding key has to be unique. A HashMap is a collection class based upon MutableMap interface and it does that by implementing MutableMap interface of HashTable. Kotlin provides four types of constructor to define and manipulate HashMap.HashMap() – It is the default constructor which helps us create an empty HashMap.HashMap(initialCapacity: Int, loadFactor: Float = 0f) – It helps us create a HashMap using initial capacity; if it is not provided, then it will be ignored and it will act as default HashMap().HashMap(initialCapacity: Int) – It ...
Read MoreHow to use SharedPreferences on Android to store, read and edit values using Kotlin?
This example demonstrates how to use SharedPreferences on Android to store, read and edit values using Kotlin.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.ktimport android.content.SharedPreferences import android.os.Bundle import android.view.View import android.widget.EditText import android.widget.TextView import android.widget.Toast import androidx.appcompat.app.AppCompatActivity class MainActivity : AppCompatActivity() { lateinit var editTextName: EditText private lateinit ...
Read MoreHow to pass data between Activities on an Android application using Kotlin?
This example demonstrates how to pass data between Activities on an Android application using Kotlin.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.ktimport android.content.Intent import android.os.Bundle import android.widget.Button import android.widget.TextView import androidx.appcompat.app.AppCompatActivity class MainActivity : AppCompatActivity() { private val myRequestCode = 1 override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) ...
Read MoreHow to call OnDestroy Activity in an Android App using Kotlin?
This example demonstrates how to call OnDestroy Activity in an Android App using Kotlin?Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.ktimport android.os.Bundle import android.util.Log import android.widget.Toast import androidx.appcompat.app.AppCompatActivity class MainActivity : AppCompatActivity() { private val myTag = "Destroy" override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) title = "KotlinApp" ...
Read MoreHow to get the current date and time from the internet in Android using Kotlin?
This example demonstrates how to get the current date and time from the internet in Android using Kotlin.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.ktimport android.os.Bundle import android.widget.Button import android.widget.TextView import androidx.appcompat.app.AppCompatActivity import java.text.SimpleDateFormat import java.util.* class MainActivity : AppCompatActivity() { lateinit var calendar: Calendar lateinit var simpleDateFormat: SimpleDateFormat lateinit var date: String lateinit ...
Read MoreHow to write files to the assets folder in android using Kotlin?
This example demonstrates how to write files to the assets folder in android using Kotlin.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.ktimport android.os.Bundle import android.widget.Button import android.widget.TextView import androidx.appcompat.app.AppCompatActivity import java.io.IOException import java.io.InputStream class MainActivity : AppCompatActivity() { lateinit var textView: TextView lateinit var button: Button override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) ...
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