Android Terminologies , Resources and Animation For BCA Semester 3 or IT Students

 Prepared By : Prof. Uday Shah (HOD-IT)

Android Terminologies

Android Terminologies

• Context

• Context is an abstract class in Android used to access application-specific resources and classes.

• It provides access to application environment data like databases, shared preferences, and system services.

• Activities, Services, and Applications are subclasses of Context.

• It is essential to start components like activities or services using startActivity() or startService().

• Context is required to access resources via getResources() or launch a Toast message.

• There are two main types: Application Context and Activity Context.

• Application Context is tied to the application lifecycle, while Activity Context is tied to the activity lifecycle.

• Misuse of context can lead to memory leaks, especially if you hold references to activity context in static objects.

• It helps in inflating views using LayoutInflater.

• Context is often passed to classes and adapters that require access to resources.

• Activity

• Activity is a single screen with a user interface in an Android application.

• It is the entry point for interacting with the user and handling UI events.

• Each activity goes through a lifecycle: onCreate(), onStart(), onResume(), onPause(), onStop(), onDestroy().

• Defined in the AndroidManifest.xml to be recognized by the system.

• An app may contain multiple activities for different screens or functions.

• Activities can launch other activities using intents.

• They manage fragments and support multitasking with the back stack.

• UI for an activity is usually defined in an XML layout file.

• The activity manages the user input and interaction logic.

• It plays a central role in UI design and navigation in Android.

• Intent

• Intent is a messaging object used to request an action from another app component.

• Intents are used to start activities, start services, and broadcast messages.

• There are two types: Explicit Intent (targets a specific component) and Implicit Intent (asks system to find component).

• Intents can carry data using extras (putExtra(), getExtra()).

• They are used to open system components (camera, browser, etc.).

• Intent Filters are declared in the manifest to handle implicit intents.

• It enables component reusability and communication between components.

• Intents are also used for navigation between screens.

• startActivityForResult() uses intent to get results back from another activity.

• Proper use of intents improves modularity and inter-app communication.

• Service

• Service is an Android component used to perform background operations.

• It does not provide a user interface.

• Useful for long-running tasks like downloading files, playing music, or network calls.

• Services can be started (startService()) or bound (bindService()).

• onStartCommand() is called when a service is started.

• Services continue to run even if the user switches activities.

• Android provides Foreground Services to indicate ongoing tasks to users.

• Must be stopped using stopSelf() or stopService() to avoid resource leakage.

• Services can run on the main thread, but for heavy operations, use IntentService or WorkManager.

• Properly managing services is essential to optimize battery and performance.

• Broadcast Receiver

• BroadcastReceiver allows apps to listen for and respond to broadcast messages from the system or other apps.

• Common system broadcasts include battery low, connectivity changes, or boot completed.

• You can define a broadcast receiver by extending BroadcastReceiver and overriding onReceive().

• Receivers can be registered statically in the manifest or dynamically in code.

• Used for receiving messages in the background without UI.

• Receivers are often used with alarms or scheduled tasks.

• They are lightweight and should do quick processing only.

• For longer tasks, use a service inside onReceive() to offload the work.

• They help apps stay reactive to system-level changes.

• Security is important; define permissions if needed to restrict broadcasts.

• Fragment

• A Fragment represents a reusable portion of the user interface inside an activity.

• It has its own lifecycle, separate from the activity, but still tied to it.

• Multiple fragments can be combined in one activity to support multi-pane UI (like in tablets).

• Defined using XML or Java/Kotlin and added via FragmentManager.

• Common lifecycle methods: onAttach(), onCreateView(), onStart(), onResume(), etc.

• Allows modular design and code reuse between activities.

• Communicates with its host activity using interfaces or ViewModel (in MVVM pattern).

• Fragments can be dynamically added, removed, or replaced during runtime.

• Supports back stack navigation.

• They are essential for building responsive UIs for various screen sizes.

• Fragments improve app flexibility and adaptability.

Resources

• Working with Different Types of Resources:

➤ String

• Defined in res/values/strings.xml.

• Used for text values like labels, messages, and UI text.

• Accessed in code using getString(R.string.name).

• Supports localization and easy maintenance of text.

• Reduces hardcoding in Java/Kotlin code.

• Enables translation of app into multiple languages.

• Placeholders (%s, %d) allow formatted strings.

• Best practice to define all UI text in strings.xml.

• Reduces redundancy and increases code clarity.

• Can be used in XML layouts using @string/name.

➤ Integer

• Stored in res/values/integers.xml.

• Used for numeric constants, dimensions, or configuration values.

• Accessed using getResources().getInteger(R.integer.value_name).

• Helps in reusing numeric values across the app.

• Useful for app settings or UI configurations.

• Integer arrays can also be defined and used in adapters.

• Avoids magic numbers in code.

• Encourages better maintainability.

• Supports device-specific tuning if placed in resource qualifiers.

• Helps separate logic from configuration.

➤ Drawable

• Used for images, shapes, vectors, and graphic content.

• Stored in the res/drawable folder.

• Can include .png, .jpg, .xml vector files or shape drawables.

• Used in backgrounds, buttons, icons, etc.

• Custom shapes can be defined using XML (rectangle, gradient).

• Used in layout via android:background="@drawable/image".

• Easily scalable across screen densities.

• Android Studio supports vector drawables for performance.

• Helps create consistent and visually rich UIs.

• Can be animated using drawable animation.

➤ Color

• Stored in res/values/colors.xml.

• Defines app color palette using HEX values.

• Used in UI elements like buttons, backgrounds, and text.

• Can be accessed in code (ContextCompat.getColor()) and XML (@color/name).

• Supports theming and material design.

• Encourages reuse and consistency of color across the app.

• Helps in applying night mode using color state lists.

• Different resources can be defined for light/dark mode.

• Used in defining themes and styles.

• Improves UI aesthetics and accessibility.

➤ Style

• Stored in res/values/styles.xml.

• Defines appearance attributes for UI elements.

• Helps in applying consistent look across multiple views.

• Used to define font size, padding, colors, etc.

• Reduces redundancy in layout files.

• Supports inheritance using parent attribute.

• Can be applied in layouts using style="@style/StyleName".

• Encouraged for scalable and maintainable UI.

• Promotes adherence to Material Design Guidelines.

• Themes can be created using styles for full-app customization.

Animation

• Tween Animation

• Tween (in-between) animation modifies an object’s properties over time.

• Includes effects like translate, rotate, scale, and fade (alpha).

• Defined in XML inside res/anim folder.

• Applies to Views and starts using startAnimation().

• Lightweight and does not affect view's actual position or state.

• Example: A button slides in from the left.

• Useful for basic visual effects in UI.

• Does not allow complex frame changes or drawable switching.

• Can be chained using animation sets.

• Commonly used in splash screens and transitions.

• Frame-by-Frame Animation

• Displays a sequence of drawable images (like a flipbook).

• Defined using AnimationDrawable in XML (res/drawable/animation_list.xml).

• Each frame has a duration, and animation loops or stops.

• Suitable for animations like loading indicators or cartoons.

• Starts using start() method in Java/Kotlin.

• Requires multiple drawable resources (images).

• Heavier on memory compared to tween.

• Can simulate realistic animations.

• Often used in games or fun visual effects.

• Should manage resource cleanup to avoid memory issues.

:: Best of Luck ::