Android Interview Questions and Answers

1. What are the key components of Android Architecture?

Android Architecture consists of 4 key components:

·         Linux Kernel

·         Libraries

·         Android Framework

·         Android Applications

2. What are the advantages of having an emulator within the Android environment?

·         The emulator allows the developers to work around an interface which acts as if it were an actual mobile device.

·         They can write, test and debug the code.

·         They are safe for testing the code in early design phase

3. Tell us something about activityCreator?

·         An activityCreator is the initial step for creation of a new Android project.

·         It consists of a shell script that is used to create new file system structure required for writing codes in Android IDE.

4. What do you know about Intents?

·         Notification messages to the user from an Android enabled device can be displayed using Intents. The users can respond to intents.

·         There are two types of Intents - Explicit Intent, Implicit Intent.

5. What is an Explicit Intent?

·         Explicit intent specifies the particular activity that should respond to the intent.

·         They are used for application internal messages.

6. What is an Implicit Intent?

·         In case of Implicit Intent, an intent is just declared.

·         It is for the platform to find an activity that can respond to it.

·         Since the target component is not declared, it is used for activating components of other applications.

7. What do intent filters do?

·         There can be more than one intents, depending on the services and activities that are going to use them.

·         Each component needs to tell which intents they want to respond to.

·         Intent filters filter out the intents that these components are willing to respond to.

8. Where are lay out details placed? Why?

·         Layout details are placed in XML files

·         XML-based layouts provide a consistent and standard means of setting GUI definition format.

9. What do containers hold?

·         Containers hold objects and widgets in a specified arrangement.

·         They can also hold labels, fields, buttons, or child containers. .

10. What is Orientation?

·         Orientation decides if the LinearLayout should be presented in row wise or column wise fashion.

·         The values are set using setOrientation()

·         The values can be HORIZONTAL or VERTICAL

11. What is it important to set permissions in app development?

·         Certain restrictions to protect data and code can be set using permissions.

·         In absence of these permissions, codes could get compromised causing defects in functionality.

12. What is AIDL?

·         AIDL is the abbreviation for Android Interface Definition Language.

·         It handles the interface requirements between a client and a service to communicate at the same level through interprocess communication.

·         The process involves breaking down objects into primitives that are Android understandable.

13. What data types are supported by AIDL?

AIDL supports following data types:

·         string

·         List

·         Map

·         charSequence

·         all native Java data types like int,long, char and Boolean

14. Tell us something about nine-patch image.

·         The Nine-patch in the image name refers to the way the image can be resized: 4 corners that are unscaled, 4 edges that are scaled in 1 axis, and the middle one that can be scaled into both axes.

·         A Nine-patch image allows resizing that can be used as background or other image size requirements for the target device.

15. Which dialog boxes are supported by android?

Android supports 4 dialog boxes:

a.) AlertDialog: Alert dialog box supports 0 to 3 buttons and a list of selectable elements which includes check boxes and radio buttons.

b.) ProgressDialog: This dialog box is an extension of AlertDialog and supports adding buttons. It displays a progress wheel or bar.

c.) DatePickerDialog: The user can select the date using this dialog box.

d.) TimePickerDialog: The user can select the time using this dialog box.

16. What is Dalvik Virtual Machine?

·         It is Android's virtual machine.

·         It is an interpreter-only virtual machine which executes files in Dalvik Executable (.dex) format. This format is optimized for efficient storage and memory-mappable execution.