JNTU MCA 2021 MOBILE APPLICATION DEVELOPMENT Previous Question Paper (February - 2021 - R17)

An Activity is a fundamental component of an Android application that provides a single screen with which users can interact. It acts as the entry point for a user's interaction with the app, managing the user interface and handling events. Every activity is implemented as a subclass of the Activity class.

The Activity Lifecycle consists of a series of callback methods that the system invokes as an activity transitions between different states. These methods allow developers to manage resources and maintain the state of the application.

• onCreate(): Called when the activity is first created. This is where you perform static setup like creating views and binding data to lists.
• onStart(): Called when the activity becomes visible to the user.
• onResume(): Called when the activity starts interacting with the user. The activity is now at the top of the activity stack.
• onPause(): Called when the system is about to start resuming a previous activity. This is 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, just prior to it being started again.
• onDestroy(): The final call received before the activity is destroyed, either because the user finished the activity or the system is temporarily destroying it to save space.

Managing these states correctly is critical for preventing memory leaks, ensuring the application remains responsive, and preserving user data during configuration changes or system-initiated interruptions.

An Android Virtual Device (AVD) is a configuration profile that defines the characteristics of an Android device, including its hardware specifications, software version, and screen resolution. It acts as an emulator instance that runs on a development machine, allowing developers to test and debug mobile applications without needing a physical device for every possible hardware configuration.

The AVD configuration specifies the system image (Android version), device hardware profile (e.g., Pixel 5, Nexus 7), internal storage capacity, and sensors like GPS or accelerometer. It creates a sandbox environment that mimics the behavior of a real device, including the ability to simulate incoming calls, SMS, and network conditions.

Steps to create an AVD in Android Studio:

1. Open Android Studio and navigate to the Device Manager tool window, usually found in the right-hand sidebar or via the Tools menu.
2. Click the Create Device button to launch the Virtual Device Configuration wizard.
3. Select a hardware profile from the list (e.g., Phone, Tablet, Wear OS) and click Next.
4. Choose a system image (Android API level) from the Recommended or x86 Images tabs. If the image is not downloaded, click the Download icon next to the version and wait for the process to complete, then select it and click Next.
5. Verify the configuration settings, such as AVD Name, startup orientation, and graphics acceleration settings. You can click Show Advanced Settings to configure camera, network, and storage parameters.
6. Click Finish to save the AVD. The new device will appear in the Device Manager list, where it can be launched by clicking the Play icon.