The team at GoApti has prepared a list of 10 Android developer interview questions for strengthening your concepts and understanding.
The stats for the demand of Android developers are astonishingly high. The market is filled with android devices and applications. And this naturally means companies are on the constant lookout for Android experts.
1. Why do you find yourself fit for the position of an Android developer and why should we hire you?
One of the prominent Android developer interview questions you are most likely to be asked is what makes you a good Android developer. Talk about:
- The apps you have built to learn and explore Android. If possible, provide approximate statistics on how many times people have used or downloaded them.
- The latest libraries you have used.
- New features that haven’t become mainstream yet.
- Android tips and tricks you use.
When you have so much to say, the interviewer won’t doubt your technical expertise. Don’t bluff anything because you’ll get caught sooner or later.
2. What is the Google Android SDK?
The Google Android SDK is a toolset for writing apps on Android enabled devices. It contains a graphical interface that emulates an Android driven handheld environment, allowing them to test and debug their codes. YOu need an Android emulator, right?
3. Explain the Platform Architecture of Android.
Android is an open-source, LINUX based software pack. It mainly comprises of Linux Kernel, Hardware Abstraction Layer, Native libraries, Android Runtime, Java API, and System Apps. Starting from the bottom-most layer in the architecture, the Linux kernel provides drivers for connecting to the hardware. The driver’s list contains audio, binder, display, keypad, Bluetooth, camera, USB, Wi-Fi, and power management.
The Hardware Abstraction Layer (HAL) provides a standard that interacts with Kernel drivers for the users to access these hardware features. ART (Android Runtime) is there to help when multiple virtual machines (VM’s) are run on low memory devices with the execution of DEX files. C or C++ is needed to build the native code. Android provides Java APIs to use the functionalities of native libraries in the apps. Java APIs form the building blocks needed to create Android apps by providing the components and services. Android comes with a set of core apps for emails, SMS messages, calendars, internet browsing, contacts, and more.
4. Explain the Android activity lifecycle?
Android developer interview questions are incomplete with the activity lifecycle. After a user navigates within the app, the activity instances transit through different stages in their lifecycle. These activity classes provide several actions known as “callbacks” that give information on the changed states the system creates, resumes, or stops while resuming the activity. The activity life cycle has 4 states:
- Active or running – If the activity is in the foreground of the screen, it is active.
- Paused – If the activity has lost focus but is still visible (in the case of a dialog box), then it becomes paused.
- Stopped – If an activity is completely obscured by another activity, it’s in the stop state. It still retains all the states and the information of member components.
- Finish – If an activity is paused or stopped, the system can drop the activity from memory by either asking it to finish or simply killing the process.
5. What is a service in Android and what are the types of services?
A service is an application component that can perform long-running operations in the background, and it does not provide a user interface. There are 3 types of services:
- Scheduled: A service is scheduled when an API such as JobScheduler launches the service.
- Started: A service is started when an application component (activity) calls startservice(). After service starts, it can run in the background indefinitely, even if the components that started it are destroyed. It is stopped by the stopService() method. The service can stop itself by calling the stopSelf() method.
- Bound: A service is bound when an application component binds to it by calling bindservice(). Abound service offers a client-server interface that allows components to interact with the service, send requests, and receive a request. The client can unbind the service by calling the unbindservice() method. The service cannot be stopped until all the clients unbind the service.
6. What are the different ways to define the service’s IBinder interface?
The different ways to define the service’s IBinder interface and pass it to the client (just like activities) are:
- Extending the Binder class
- Using a Messenger
- Android Interface Definition Language (AIDL)
Extending the Binder class: If the services are private to the applications and run in the same process as the client, then the interface can be created by extending the Binder class and returning an instance of it from onBind(). The client receives the Binder and can use it to directly access public methods available in the Binder implementation or the service.
7. What is an intent in Android and what are the types of intent?
An intent is a messaging object. If a developer is trying to pass the data from one screen to another screen, he or she uses an intent. There are 2 types of intent:
- Implicit: Implicit intent calls the system components.
- Explicit: Explicit intent invokes the activity class.
8. Mention the Android OS versions you remember.
- Android 4.0: Android Ice Cream Sandwich
- Android 4.1 to 4.3.1: Android Jelly Bean
- Android 4.4 to 4.4.4: Android KitKat
- Android 5.0 to 5.1.1: Android Lollipop
- Android 6.0 to 6.0.1: Android Marshmallow
- Android 7.0 to 7.1: Android Nougat
- Android 8.0 to Android 8.1: Android Oreo
- Android 9.0: Android Pie
- Android 10.0: Android Q. Officially Called as Android 10
9. What components/requirements are required for Android development projects?
The components needed for successful completion of Android projects are:
- Build: Contains the build output.
- Src: Holds the code and resource file.
- Res: Holds the bitmap images, UI, and XML layouts.
- Assets: Holds the file which can be combined into a .apk file.
- Manifest: Holds the XML file.
10. What do you mean by AIDL and what data types are supported in AIDL?
AIDL stands for Android Interface Definition Language. AIDL facilitates communication between the client and the service. The data types supported in AIDL are:
- Java data types
What Android developer interview questions are you aware of? What’s your preferred Android emulator? Are there any relevant certifications one should do? We’d love to hear from you in the comments.