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
and
-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.