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.
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 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 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.
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.
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.
Difference Between List and Array in Kotlin
Learn the difference between List and Array in Kotlin, including mutability, size, APIs, performance, and when to use each one.
Fix Hilt Unsupported Metadata Version Error in Kotlin
Learn why Hilt fails with an unsupported metadata version in Kotlin and how to fix version incompatibility in Android projects.
Fix Incompatible Kotlin Metadata Version Error in Android/Gradle
Learn why the Kotlin metadata version error happens in Android builds and how to fix mismatched Kotlin and Gradle versions safely.
Fix KaptExecution Error in Android Kotlin: Data Binding and Build Generation
Learn why KaptExecution fails in Android Kotlin builds, especially with data binding and generated classes, and how to fix it step by step.
Fix Kotlin Version Mismatch Between Gradle and Android Studio Plugin
Learn why Kotlin version mismatch happens between Gradle and Android Studio, and how to fix it safely in Android projects.
Fix PendingIntent FLAG_IMMUTABLE or FLAG_MUTABLE Error in MediaSessionCompat on Android 12+
Learn why MediaSessionCompat crashes on Android 12+ with PendingIntent flags and how to fix it using updated AndroidX media libraries.
Fix compileJava and compileKotlin JVM Target Mismatch in Gradle Kotlin DSL
Learn how to set matching Java and Kotlin JVM targets in build.gradle.kts and fix compileJava 11 vs compileKotlin 1.8 errors.
Fixing "Default Interface Methods" Error in Android: Java 8, D8, and LifecycleObserver
Learn why Android shows the default interface methods error, how Java 8 affects minSdk, and how to fix it with D8 and Android lifecycle libraries.
Fixing "Inappropriate Blocking Method Call" in Kotlin Coroutines
Learn why Kotlin shows "inappropriate blocking method call" and how to correctly use blocking APIs like OkHttp and Moshi in coroutines.
Fixing "navigation destination is unknown to this NavController" in Android Navigation
Learn why Android Navigation throws "destination is unknown to this NavController" and how to fix graph, action, and Fragment issues.
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