JNTU B.Tech III MOBILE APPLICATION DEVELOPMENT Previous Question Paper (August/September - 2021 - R18)

An Android Virtual Device (AVD) is an emulator configuration that allows developers to model an actual Android device. It acts as a software-based representation of a specific Android phone, tablet, or wearable, enabling the testing of applications without requiring physical hardware. An AVD defines the hardware characteristics, such as screen size, resolution, memory, and sensors, as well as the system image (Android version) to be executed.

To create an AVD in Android Studio, follow these steps:

1. Open the Device Manager from the Android Studio toolbar or the Tools menu.
2. Click on the Create Device button.
3. Select a hardware profile (e.g., Pixel 7) from the list and click Next.
4. Choose a system image (e.g., Android 13.0) and download it if necessary, then click Next.
5. Verify the configuration settings, such as AVD Name, Startup orientation, and Graphics performance, then click Finish.

Android applications are broadly categorized into the following types:

• Native Applications: Developed specifically for the Android platform using Java or Kotlin with the Android SDK. They provide the best performance and full access to device hardware like the camera, GPS, and sensors.
• Web Applications: These are essentially websites optimized for mobile browsers. They are platform-independent but lack deep integration with device hardware and require an active internet connection.
• Hybrid Applications: A combination of native and web technologies. They are built using web technologies (HTML, CSS, JavaScript) and wrapped in a native container (like WebView) to access device features. Frameworks like Flutter, React Native, and Ionic are commonly used.
• Progressive Web Apps (PWAs): Web applications that provide a native-like experience, including offline capabilities via service workers and the ability to be added to the home screen, without the need for installation through an app store.

The Activity Lifecycle is a set of states an activity transitions through from its creation to its destruction. The lifecycle is managed by the Android system through a series of callback methods.

Lifecycle Diagram Description: The lifecycle begins at the Launched state, moving to Created, Started, and Resumed (running). When interrupted, it moves to Paused or Stopped, and finally to Destroyed.

Callback Methods:

• onCreate(): Called when the activity is first created. Used for static setup like binding data to lists or initializing UI components.
• onStart(): Called when the activity becomes visible to the user.
• onResume(): Called when the activity starts interacting with the user. The activity is at the top of the stack.
• onPause(): Called when the activity is partially obscured or another activity is coming to the foreground. Used to commit unsaved changes or stop animations.
• onStop(): Called when the activity is no longer visible to the user.
• onRestart(): Called after the activity has been stopped, prior to it being started again.
• onDestroy(): The final call received before the activity is destroyed.

Coding Snippet:

public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override protected void onStart() { super.onStart(); // Activity is becoming visible } @Override protected void onResume() { super.onResume(); // Activity is now interacting with user } @Override protected void onPause() { super.onPause(); // Activity is being paused } @Override protected void onStop() { super.onStop(); // Activity is no longer visible } @Override protected void onDestroy() { super.onDestroy(); // Activity is being destroyed } }