• MainActivity serves as the main entry point of the application.
• It handles user authentication, navigation between different fragments, and SharedPreferences management for storing user information and authentication tokens.

• Method called when the activity is first created.
• Sets the content view to activity_main layout.
• Checks if the user is already authenticated by checking if their token exists in SharedPreferences.
  • If authenticated, replaces the container view with PostsFragment.
  • If not authenticated, replaces the container view with LoginFragment.

• Navigates to SignUpFragment by replacing the container view.

• Saves user information and authentication token to SharedPreferences after successful authentication.
• Replaces the container view with PostsFragment after authentication.

• Navigates to LoginFragment by replacing the container view.

• Deletes user information and authentication token from SharedPreferences upon logout.
• Navigates to LoginFragment after logout and adds the transaction to the back stack.
• Logs a debug message indicating SharedPreferences deletion.

• Navigates to CreatePostFragment by replacing the container view and adding the transaction to the back stack.

• Pops the back stack to return to the previous fragment (PostsFragment).

• Checks if the user is authenticated by retrieving token and user information from SharedPreferences.
• Returns true if token and user information are present, indicating the user is authenticated.

• LoginFragment handles user login functionality by sending HTTP requests to the server's /login API endpoint.
• It also includes UI elements for entering email and password, as well as buttons for logging in and creating a new account.

• Inflates the layout for this fragment using data binding.

• Sets up click listeners for the login and create new account buttons.
• Sets the title of the activity to the login label.

• Makes an asynchronous HTTP POST request to the server's /login API endpoint with the provided email and password.
• Handles the response from the server, parsing JSON data to create an AuthResponse object upon successful login.
• Shows toast messages on the UI thread to inform the user about the success or failure of the login attempt.

• Displays a toast message on the UI thread.

• Attaches the LoginListener interface to the hosting activity to communicate events back to MainActivity.

• Defines the LoginListener interface with methods for creating a new account and completing the authentication process.  

• SignUpFragment facilitates user registration by sending HTTP POST requests to the server's /signup API endpoint.
• It includes UI elements for entering user information such as name, email, and password.

• Inflates the layout for this fragment using data binding.

• Sets up click listeners for the cancel and signup buttons.
• Sets the title of the activity to the create account label.

• Makes an asynchronous HTTP POST request to the server's /signup API endpoint with the provided user information.
• Handles the response from the server, parsing JSON data to create an AuthResponse object upon successful user registration.
• Shows toast messages on the UI thread to inform the user about the success or failure of the registration attempt.

• Displays a toast message on the UI thread.

• Attaches the SignUpListener interface to the hosting activity to communicate events back to MainActivity.

• Defines the SignUpListener interface with methods for navigating to the login screen and completing the authentication process.  

• PostsFragment displays a list of posts fetched from the server's /posts API endpoint.
• It allows users to view posts, navigate between pages of posts, create new posts, and delete their own posts.

• Inflates the layout for this fragment using data binding.

• Sets up UI components, such as buttons and RecyclerView, and initializes adapter and layout manager.
• Fetches user token from SharedPreferences and updates UI with user's name.
• Sets click listeners for buttons to handle creating new posts, logging out, and navigating between pages of posts.
• Initiates the first request to fetch posts upon fragment creation.

• Makes an asynchronous HTTP GET request to the server's /posts API endpoint with the page number and user token as parameters (& header for authentication).
• Handles the response from the server, parses JSON data to create Post objects, and updates the UI with the retrieved posts.

• Calculates and sets the total number of pages of posts to be displayed based on the total post count.

• Manages the RecyclerView for displaying posts.
• Implements onCreateViewHolder(), onBindViewHolder(), and getItemCount() methods for populating and updating the UI with posts.

• Manages individual items in the RecyclerView.
• Binds post data to UI elements and sets up click listener for deleting posts.

• Makes an asynchronous HTTP POST request to the server's /posts/delete API endpoint with the post ID and user token as parameters.
• Handles the response from the server and refreshes the list of posts if the deletion is successful.

• Defines the PostsListener interface with methods for logging out and creating new posts.  

• CreatePostFragment allows users to create new posts by sending HTTP POST requests to the server's /posts/create API endpoint.
• It includes UI elements for entering the text of the post and buttons for submitting or canceling the post creation.

• Inflates the layout for this fragment using data binding.

• Sets up UI components and click listeners for the cancel and submit buttons.
• Sets the title of the activity to the create post label.

• Makes an asynchronous HTTP POST request to the server's /posts/create API endpoint with the post text and user token as parameters (& header for authentication).
• Handles the response from the server, displaying toast messages to inform the user about the success or failure of the post creation.

• Displays a toast message on the UI thread.

• Defines the CreatePostListener interface with a method for navigating back to the posts fragment after post creation.  

• The Post class represents a post object retrieved from the server's API.
• It implements the Serializable interface to allow for serialization and passing between activities/fragments.
• The class contains attributes representing various properties of a post, such as creator name, ID, text, creation timestamp, etc.

• The constructor initializes a Post object using a JSON object received from the server's API response.
• It extracts relevant data from the JSON object and assigns it to the corresponding attributes of the Post object.

• Provides getter methods for accessing the attributes of the Post object.

• Overrides the toString() method to provide a string representation of the Post object for debugging purposes.  

• The AuthResponse class represents the response received from the server upon successful authentication or login.
• It contains attributes for user ID, user full name, and authentication token.

1. Default Constructor: Initializes an empty AuthResponse object.
2. Parameterized Constructor: Initializes an AuthResponse object using a JSON object received from the server's API response.
   • Extracts user ID, user full name, and token from the JSON object and assigns them to the corresponding attributes of the AuthResponse object.

• Provides getter and setter methods for accessing and modifying the attributes of the AuthResponse object.

• Overrides the toString() method to provide a string representation of the AuthResponse object for debugging purposes.

All APIs Tested Using Postman