Mobile App Architecture and Android Lifecycle
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Questions and Answers

What is the primary purpose of using fragments in Android apps?

  • To restrict navigation in the app
  • To increase the size of the application code
  • To eliminate the need for lifecycle management
  • To provide Dynamic UI Design (correct)

What does an Explicit Intent specify?

  • A specific component to launch within the app (correct)
  • A universal action to be executed by any app
  • A service to communicate with background processes
  • A category of components to perform an action

Which of the following is NOT a function of an Intent in Android?

  • Starting a new interface within an app
  • Starting background services in the application
  • Receiving data from a user in real-time (correct)
  • Broadcasting a message to other devices

Which statement accurately describes an Implicit Intent?

<p>It allows for communication between different applications. (C)</p> Signup and view all the answers

What does lifecycle awareness refer to in the context of fragments?

<p>Managing the creation and destruction of application components (C)</p> Signup and view all the answers

What is the primary purpose of Mobile App Architecture?

<p>To improve app performance, maintainability, and scalability. (D)</p> Signup and view all the answers

Which architecture pattern is commonly used for Android apps?

<p>Model-View-ViewModel (MVVM) (C)</p> Signup and view all the answers

During which stage of the Android Activity Lifecycle is the Activity first created?

<p>onCreate (D)</p> Signup and view all the answers

What happens during the onPause() method of an Android Activity?

<p>Updates, animations, or audio playback are paused. (A)</p> Signup and view all the answers

Which lifecycle method should be called to set up UI components after the Activity becomes visible?

<p>onStart (D)</p> Signup and view all the answers

What is the key role of the onResume() method in the Android Activity Lifecycle?

<p>It makes the Activity interactive and starts updates. (A)</p> Signup and view all the answers

Which stage is NOT part of the Android Activity Lifecycle?

<p>onInit (C)</p> Signup and view all the answers

What should occur during the onStart() method of an Android Activity?

<p>Set up resources that should be always re-initiated. (D)</p> Signup and view all the answers

What is the primary purpose of the onStop() method in an Android Activity?

<p>To indicate that the Activity is no longer visible. (A)</p> Signup and view all the answers

Which method should be used to reinitialize resources that were released in onStop()?

<p>onRestart() (B)</p> Signup and view all the answers

When is the onDestroy() method typically called?

<p>Just before the Activity is removed from memory. (D)</p> Signup and view all the answers

What is the purpose of the line intent.putExtra("username", "JohnDoe");?

<p>To attach additional data to an Intent. (D)</p> Signup and view all the answers

Which lifecycle method is called when an Activity is first created?

<p>onCreate() (B)</p> Signup and view all the answers

What is the function of the onPause() method in the Android Activity lifecycle?

<p>To pause ongoing tasks and prepare for the Activity to be fully obscured. (A)</p> Signup and view all the answers

In the context of starting a new activity, what does startActivity(intent); do?

<p>It launches the specified activity. (A)</p> Signup and view all the answers

In which scenario would onRestart() be called in an Android Activity?

<p>When the user returns to the Activity from another Activity. (D)</p> Signup and view all the answers

Which method is used to replace a fragment in the MainActivity?

<p>getSupportFragmentManager().beginTransaction().replace() (A)</p> Signup and view all the answers

What should be done in the onCreate() method of an Android Activity?

<p>Initialize the user interface and set up the Activity's state. (A)</p> Signup and view all the answers

What will happen if savedInstanceState is not null in MainActivity?

<p>The existing fragment will be retained. (C)</p> Signup and view all the answers

What happens when detailsButton.setOnClickListener(v -> ... is called?

<p>It sets up an OnClickListener to navigate to DetailFragment. (A)</p> Signup and view all the answers

Which of the following statements about Activities in Android is FALSE?

<p>Activities cannot interact with other components of the app. (C)</p> Signup and view all the answers

How are data extras retrieved in the Second Activity?

<p>getIntent().getStringExtra(&quot;username&quot;); (B)</p> Signup and view all the answers

What does addToBackStack(null) do in the context of fragment transactions?

<p>It allows the user to navigate back to the previous fragment. (A)</p> Signup and view all the answers

What is the correct way to inflate a fragment view inside ListFragment?

<p>inflater.inflate(R.layout.fragment_list, container, false); (D)</p> Signup and view all the answers

What is the primary role of an Activity in Android?

<p>To display a user interface and handle user input. (A)</p> Signup and view all the answers

Which method is called when an Activity is launched for the first time?

<p>onCreate() (B)</p> Signup and view all the answers

What does the onPause() method indicate in the Activity lifecycle?

<p>The Activity is about to lose focus but is still partially visible. (C)</p> Signup and view all the answers

What is the purpose of using Fragments in Android applications?

<p>To create reusable UI components within an Activity. (B)</p> Signup and view all the answers

What happens during the onStop() method in the Activity lifecycle?

<p>The Activity is no longer visible to the user. (A)</p> Signup and view all the answers

How are Fragments integrated within an Activity?

<p>Fragments are typically embedded within an Activity. (B)</p> Signup and view all the answers

Which of the following best describes the Home Activity in an Android app?

<p>An entry point that shows a list of news articles. (C)</p> Signup and view all the answers

Which of the following is NOT a lifecycle method of an Activity in Android?

<p>onExit() (A)</p> Signup and view all the answers

Flashcards

Fragment

A fragment is a reusable part of a user interface that can be combined with other fragments to create more complex layouts.

Intent

Intents allow Android apps to communicate with each other and perform various tasks like starting activities.

Explicit Intent

Explicit intents are used to launch specific components within the same application.

Implicit Intent

Implicit intents can launch activities in other applications based on the intent's action and data.

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onStop()

Called when the Activity is no longer visible to the user, often when another Activity is opened.

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onRestart()

Called when the Activity becomes visible again after being stopped, like returning to the Activity from the Recent Apps menu.

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What is Mobile App Architecture?

The internal structure of a mobile app, outlining how data is handled, how the user interface is presented, and how different parts of the app connect.

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onDestroy()

The final method called before the Activity is destroyed due to the user or system.

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Why is App Architecture Important?

It influences performance, how easy it is to maintain, and how well the app can handle more users and data.

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onCreate()

Called when the Activity is created and initialized, including setting the layout and logging the creation.

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What is Android Activity Lifecycle?

The Android Activity Lifecycle is responsible for managing how activities respond to user interactions and system events, like receiving phone calls.

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onStart()

Called when the Activity becomes visible and ready to interact with the user.

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What are the Android Activity Lifecycle Stages?

The stages of an Android Activity's life: onCreate, onStart, onResume, onPause, onStop, onDestroy.

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What happens in the onCreate() Method?

Called when an activity is first created. It's when you set up the UI, bind data, and initialize components.

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onResume()

Called when the Activity comes into focus and fully functional.

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onPause()

Called when the Activity is losing focus, but still partially visible (such as when a dialog box pops up).

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What happens in the onStart() Method?

Called after onCreate, making the activity visible to the user, but not in the foreground. It's a good time to register receivers or start animations.

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What is an Activity?

Represents a single screen with a user interface in an Android app, like a web page on a website.

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What happens in the onResume() Method?

Called when the activity gains focus and becomes active. It's ideal for starting updates, animations, and data refreshes.

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What happens in the onPause() Method?

Called when the activity is partially blocked, like when a dialog appears. It's a good time to pause updates, animations, and save data.

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What is an Android Activity?

The building blocks of an Android app that represent a single screen with a user interface.

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What are Activities responsible for?

Activities are responsible for handling user interactions, such as touch events, keyboard input, and system events. They also manage transitions between different screens within the app.

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What are the stages in an Activity's lifecycle?

onCreate() - Called when the Activity is first created.onStart() - The Activity becomes visible to the user, but not interactive.onResume() - The Activity is in the foreground and interactive.onPause() - The Activity is about to lose focus, but partially visible.onStop() - The Activity is no longer visible.onDestroy() - Called before the Activity is removed from memory.

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What is an Android Fragment?

A reusable portion of an app's user interface that can be embedded within an Activity.

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Why use Fragments?

Fragments allow for modular UI design, making it easier to reuse components across multiple screens and sections of an app.

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Give an example of how Fragments are used in an app.

In a news app, a Fragment might display a list of articles, while another Fragment shows the details of a selected article. In a settings screen, each Fragment could represent a different category of settings.

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How do Fragments interact with Activities?

A Fragment occupies part or all of an Activity's screen, allowing for more complex and flexible screen layouts.

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Activity

A component in Android that represents a screen or a part of a screen, and can be reused across different parts of the application. It typically handles user interaction events and manages its own visual presentation.

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Intent Extra

A key-value pair used to pass data with an Intent. Extra data can include user-entered information, preferences, or any other data that needs to be shared.

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Activity Lifecycle

A system for managing the lifecycle of an Activity. It provides methods that are called at different points in the lifecycle, allowing you to manage resources and respond to user actions.

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Replacing a Fragment

The process of replacing an existing Fragment within a container with a new Fragment. This allows you to dynamically change the UI based on user interactions or other events.

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inflater.inflate()

A method that inflates a layout file, which describes the visual structure of a View. This method is typically used when creating a new View in a Fragment.

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getIntent()

A method used to retrieve an Intent from an Activity. This allows the Activity to access data passed through the Intent by another Activity.

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Study Notes

Mobile App Architecture

  • Mobile app architecture is the structure of an app's core components, including data, presentation, and navigation.

Why Mobile App Architecture?

  • Affects app performance, maintainability, and scalability.
  • Platform differences, such as Android (MVVM or Clean Architecture) and iOS (MVC or MVVM), exist.

Android Activity Lifecycle

  • Manages user interactions and resource handling, including pausing activities during interruptions (like phone calls).

Android Activity Lifecycle Stages and Methods

  • onCreate(Bundle savedInstanceState): Called when an Activity is first created. Initializes the activity's UI, binds data, and initializes components.
  • onStart(): Called after onCreate and displays the activity to the user, initiating actions like registering receivers and starting animations whenever the activity becomes visible.
  • onResume(): Called when the activity gains focus and becomes interactive, updating things like starting animations, refreshing UI, or updating data whenever the activity is active.
  • onPause(): Called when the activity is partially blocked, like when a dialog appears or the user navigates away. Pauses updates, animations, or audio playback, saves data, and commits changes.
  • onStop(): Called when the activity is no longer visible, often when the user opens a new activity.
  • onRestart(): Called if the activity is stopped and then restarted, such as when a user returns to it from the Recent Apps menu. Re-initializes any resources released in onStop.
  • onDestroy(): Called before the activity is fully destroyed due to user or system-initiated actions. Cleans up remaining resources, ends background tasks, and performs any final state persistence.

Components of Android Apps - Activities

  • An Activity is a single screen UI element, e.g., a news feed, editing a document, or navigating a map.

Purpose of Activities

  • Displays user interfaces for interaction.
  • Handles user input.
  • Manages transitions between screens.
  • Acts as an entry point to an app.

Activity Lifecycle (detailed steps)

  • onCreate(): Called when the Activity is first created.
  • onStart(): The Activity is visible to the user, but not yet fully in the foreground.
  • onResume(): The Activity is interactive and in the foreground.
  • onPause(): The Activity is about to lose focus.
  • onStop(): The Activity is no longer visible.
  • onDestroy(): The Activity is completely destroyed from memory.

Components of Android Apps - Fragments

  • Fragments are reusable UI elements embedded within an Activity.
  • They allow for modular design for reuse across various screens/sections of an app.

Purpose of Fragments

  • Reusability
  • Dynamic UI Design
  • Simplified Navigation
  • Lifecycle Awareness

Components of Android Apps - Intents

  • Intents are abstract descriptions of actions/operations.
    • Start new activities
    • Start services (background)
    • Send messages to other apps
    • Pass data

Types of Intents

  • Explicit Intent: Launches a specific component within the same app.
  • Implicit Intent: Allows communication between different apps.

Passing Data Using Intents

  • Use putExtra() in the intents to carry data (e.g., String data).

Implementing Activities & Fragments in Android (Coding examples)

  • Code examples demonstrate using Activities and Fragments to create Android applications, show content in layouts, etc.

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Description

This quiz explores the core components of mobile app architecture and its importance for performance and maintainability. It also covers the Android activity lifecycle stages and methods, detailing how they manage user interactions and resource handling.

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