Android Development Interview Questions

What is an activity in Android development?

In Android development, an activity is a single, focused task that a user can perform. It represents a user interface screen in an application, typically containing widgets such as buttons, text fields, and images. Activities are an essential component of an Android application's user interaction and navigation flow.

Explain the activity lifecycle in Android.

The activity lifecycle in Android consists of states like onCreate, onStart, onResume, onPause, onStop, onRestart, and onDestroy. When the activity is launched, these methods are called in a specific order based on the activity's state changes like starting, pausing, stopping, restarting, or being destroyed.

What is a fragment in Android?

A fragment in Android is a modular section of an activity that represents a portion of a user interface or behavior. Fragments can be thought of as reusable components that can be combined together to create a multi-pane UI for tablets or responsive UIs for different screen sizes.

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What are the differences between activities and fragments?

Activities are individual screens in an Android app, each containing a UI and functionality. Fragments are reusable components within activities, allowing for more modular and flexible design. Fragments can be added, removed, and replaced within an activity, enabling better responsiveness and management of app layout.

What is an intent in Android?

In Android, an intent is a class that provides a messaging structure for communication between components such as activities, services, broadcast receivers, and content providers. It is used to request an action from another app component or to deliver response data back to the originating component.

Differentiate between explicit and implicit intents.

Explicit intents are used to start a specific component within your app, such as launching an activity or starting a service. On the other hand, implicit intents are more generic and can trigger any component that is registered to handle the specific action or data type specified in the intent.

What is a service in Android?

A service in Android is a component that runs in the background to perform long-running operations independently of an application's lifecycle. Services can continue to run even when the application is not actively in use, making them ideal for tasks such as playing music, handling network requests, or syncing data.

Explain the difference between bound and unbound services.

Bound services are components that are bound to the lifecycle of another application component and are typically used for interprocess communication. Unbound services are components that run independently of other components and are initiated by calling `startService()` which allows them to run in the background without being tied to another component.

What is a content provider in Android?

A content provider in Android is a component that manages access to a central repository of data. It allows different applications to securely access and share data, enabling inter-process communication. Content providers are often used to store and retrieve data from databases, files, or network sources.

How to efficiently perform background tasks in Android?

To efficiently perform background tasks in Android, use AsyncTask or Kotlin coroutines for short-running tasks, while for long-running tasks consider using JobScheduler, WorkManager, or Firebase JobDispatcher. Utilize IntentService for handling asynchronous tasks, and make use of Foreground Service for tasks that require the user's attention.

What is a BroadcastReceiver in Android?

A BroadcastReceiver in Android is a system component that allows the app to receive and react to broadcast messages from the system or other apps. It can be used to trigger actions based on various events like screen turning on/off, battery low, incoming calls, etc.

How to create a custom view in Android?

To create a custom view in Android, you need to create a new class that extends either View or one of its subclasses. Override the onDraw method to define the view's appearance and behavior. You can then use this custom view in your XML layouts or programmatically in your code.

Explain the use of AsyncTask in Android development.

AsyncTask in Android development is used to perform background operations and update the UI thread with the results. It allows you to run tasks such as network operations or database queries off the main UI thread to prevent blocking and freezing the app. It provides methods for pre-execution, background execution, and post-execution tasks.

What are some best practices for optimizing Android app performance?

Some best practices for optimizing Android app performance include using efficient data structures, minimizing resource-intensive processes, utilizing background tasks, implementing proper caching mechanisms, optimizing image loading, reducing network calls, and regularly profiling and testing the app for bottlenecks. Additionally, following Android's guidelines and best coding practices can also help improve performance.

What is the purpose of the AndroidManifest.xml file?

The AndroidManifest.xml file is a essential configuration file in Android development. It contains important information about the app such as permissions, components (activities, services, receivers), and other metadata. It also ensures proper functioning of the app by declaring essential configurations required by the Android OS.

How to handle orientation changes in Android applications?

To handle orientation changes in Android applications, you can use the onConfigurationChanged() method in your Activity to detect when the orientation changes. You can also use the onSaveInstanceState() method to save and restore important data during orientation changes. Another option is to use Fragments to retain UI components.

What is the difference between Serializable and Parcelable interfaces in Android?

In Android development, Serializable is a standard Java interface used for object serialization, while Parcelable is an Android-specific interface used for passing data between components within an app. Parcelable is more efficient than Serializable since it is optimized for use in Android applications.

Explain the purpose of Gradle in Android development.

Gradle is a build automation tool used in Android development to automate the process of building, testing, and deploying the app. It manages project dependencies, compiles the source code, and packages the app for distribution. Gradle streamlines the development process and ensures consistency across different development environments.

What is ProGuard and how is it used in Android development?

ProGuard is a code obfuscation tool used in Android development to help reduce the size of compiled code and make it harder for reverse engineering. It renames classes, fields, and methods with shorter, meaningless names while removing unused code to improve app performance and security.

How to implement push notifications in an Android app?

To implement push notifications in an Android app, you would need to use a cloud messaging service like Firebase Cloud Messaging (FCM) or Google Cloud Messaging (GCM). You will need to set up the necessary configurations, obtain API keys, and handle message reception in your app using a service.

What is an activity in Android development?

In Android development, an activity is a single, focused task that a user can perform. It represents a user interface screen in an application, typically containing widgets such as buttons, text fields, and images. Activities are an essential component of an Android application's user interaction and navigation flow.

In Android development, an activity is a fundamental component of an application that represents a single screen with a user interface. Each activity is usually a window that contains an application-specific user interface, which users can interact with. Activities play a crucial role in the overall user experience of an Android application as they allow users to perform different tasks and navigate between different screens.

Here is an example of defining an activity in Android development:

public class MainActivity extends AppCompatActivity {
    protected void onCreate(Bundle savedInstanceState) {
        // Additional initialization code can be added here

In this code snippet, the MainActivity class extends AppCompatActivity to inherit functionality for supporting older versions of Android. The onCreate() method is overridden to perform initialization tasks when the activity is created, such as setting the layout using setContentView().

Key Points about Activities:

  • User Interface: Activities represent screens with UI elements for user interaction.
  • Lifecycle: Activities have a lifecycle that includes methods like onCreate(), onStart(), onResume(), onPause(), onStop(), and onDestroy().
  • Navigation: Activities can be started, finished, or transitioned between using intents and the activity stack.
  • Communication: Activities can communicate with each other using intents, shared preferences, bundles, or other mechanisms.

Overall, activities are essential building blocks of Android applications that provide the main user interface and interactivity. Understanding activities and their lifecycle is crucial for developing robust and user-friendly Android apps.