Questions
Kotlin questions
Choose a question page, learn the concept, then test your understanding with a quiz.
Accessing Kotlin Extension Functions from Java
Learn how Kotlin extension functions are compiled and how to call them correctly from Java with clear examples and common pitfalls.
Add a Maven Repository URL in Gradle Kotlin DSL (build.gradle.kts)
Learn how to add Maven Central and a custom Maven repository URL in Gradle Kotlin DSL using build.gradle.kts syntax.
Allow HTTP and HTTPS in Android 9 Pie with Network Security Configuration
Learn how Android 9 Pie handles cleartext HTTP traffic and how to allow HTTP and HTTPS safely using network security config.
Android AlarmManager Example: Scheduling Tasks with AlarmManager
Learn how to use Android AlarmManager to schedule tasks, set alarms, and handle broadcasts with a simple beginner example.
Android Data Binding in Kotlin: Fix Unresolved Reference Errors
Learn why Android Data Binding classes can be unresolved in Kotlin and how to configure generated bindings and fragments correctly.
Android FloatingActionButton Visibility and Restricted API Warnings in Kotlin
Learn why FloatingActionButton visibility can trigger a restricted API warning in Kotlin and when to use show(), hide(), or View visibility.
Android Foreground Service Notification Channels in Kotlin
Learn why startForeground fails on Android 8.1 and how to create a valid notification channel for foreground services in Kotlin.
Android Navigation Safe Args Directions Classes in Kotlin
Learn why Android Navigation Safe Args generates Args classes but not Directions classes, and how actions create type-safe navigation calls in Kotlin.
Android Room Main Thread Error: How to Run Queries Safely in Java/Kotlin
Learn why Room blocks database access on the main thread and how to fix it using background threads, executors, and async patterns.
Android onBackPressed Deprecation: Modern Back Handling in Kotlin
Learn the alternative to deprecated onBackPressed() in Android using OnBackPressedDispatcher and OnBackPressedCallback in Kotlin.
AsyncTask Alternatives in Android: Replacing Deprecated AsyncTask with Executor and Handler
Learn how to replace deprecated AsyncTask in Android using Executor, Handler, and modern concurrency patterns for older codebases.
Backward Ranges in Kotlin: Using downTo and step
Learn how to create backward ranges in Kotlin with downTo and step, why 100..1 is empty, and how to loop safely in descending order.
Builder Pattern in Kotlin: How to Build Objects Idiomatically
Learn how to implement the Builder pattern in Kotlin, when to use it, and which Kotlin features often replace builders.
Can You Extend a Data Class in Kotlin? Inheritance, Limits, and Better Alternatives
Learn why Kotlin data classes cannot be extended, what causes the component function clash, and which alternatives to use instead.
Check Whether a String Array Contains a Value in Kotlin
Learn how to check whether a Kotlin Array<String> contains a value using in, contains(), and any(), with examples and common mistakes.
Close the Virtual Keyboard in Jetpack Compose TextField
Learn how to hide the Android virtual keyboard after a Jetpack Compose TextField IME Done action using KeyboardActions and focus control.
Convert a Kotlin Array to Java varargs: Passing Arrays to Java Methods from Kotlin
Learn how to pass a Kotlin Array or ArrayList to a Java varargs method using the spread operator and type conversion.
Create Anonymous Interface Instances in Kotlin with SAM Conversion
Learn how to implement a Java single-method interface in Kotlin using concise SAM conversion or an object expression, with examples and pitfalls.
Create Arrays by Size in Kotlin: IntArray and Array
Learn how to create Kotlin arrays with a specified size, including IntArray for primitive integers and Array for objects.
Custom Getters in Kotlin Data Classes
Learn how Kotlin property getters work in data classes, why primary constructor properties cannot use custom accessors, and safe alternatives.
Page 1 of 9 - 162 questions