Understand MVC with Volly Network lib in Android

Hello devs, So in today's article, We learn how the MVC pattern is used and how we can use Volly for network calling or API calls.

Understanding MVC Architecture: MVC is a design pattern commonly used in software development, including Android app development. At its core, MVC separates an application into three interconnected components:

1. Model: This represents the data and business logic of the application. In an Android app, models typically encapsulate data structures and handle interactions with databases or network services.

2. View: The view is responsible for presenting the user interface and interacting with the user. In Android, views are typically implemented using XML layout files.

3. Controller: The controller acts as an intermediary between the model and the view. It handles user input, updates the model based on user actions, and updates the view to reflect changes in the model.

By separating concerns into these three components, MVC promotes a modular and maintainable codebase. Developers can make changes to one component without affecting the others, making it easier to update and extend the application over time.

Utilizing Volley Library for Network Operations: Volley is an Android library developed by Google that simplifies network operations, such as making HTTP requests and managing responses. It provides a set of powerful features, including:

1. Request Queues: Volley automatically manages a queue of network requests, optimizing network usage and ensuring that requests are processed efficiently.

2. Request Prioritization: Developers can prioritize network requests based on their importance, ensuring that critical requests are processed promptly, even in high-traffic scenarios.

3. Caching: Volley supports caching of network responses, reducing the need for repeated network requests and improving app performance.

4. Easy Integration: Volley seamlessly integrates with other Android components, such as activities and fragments, making it easy to incorporate network operations into your app.

How MVC and Volley Work Together: When building Android apps, MVC and Volley complement each other seamlessly. Here's how they can work together to create a robust and responsive application:

1. Model: In the MVC architecture, the model is responsible for handling data operations, including fetching data from remote servers using Volley. Models can encapsulate Volley requests and handle responses asynchronously, ensuring that the UI remains responsive during network operations.

2. View: Views in an Android app are responsible for presenting data to the user. With Volley, views can initiate network requests to fetch data from the server and update the UI once the data is available. By separating the view from the model, developers can create reusable and modular UI components.

3. Controller: Controllers act as intermediaries between the model and the view, handling user input and updating the model accordingly. With Volley, controllers can initiate network requests in response to user actions and update the model once the data is received. This allows for seamless communication between the different components of the application.

Let's consider a simple example of an Android app that displays a list of users fetched from a remote server using the MVC architecture and the Volley library.

1. Model:

    data class UserModel(
        val name: String,
        val email: String
    ) {
        companion object {
            fun fetchUsers(context: Context, listener: OnUsersLoadedListener) {
                val url = "https://api.example.com/users"
                val request = JsonArrayRequest(
                    Request.Method.GET, url, null,
                    { response ->
                        val users = mutableListOf<UserModel>()
                        for (i in 0 until response.length()) {
                            try {
                                val userJson = response.getJSONObject(i)
                                val user = UserModel(
                                    userJson.getString("name"),
                                    userJson.getString("email")
                                )
                                users.add(user)
                            } catch (e: JSONException) {
                                e.printStackTrace()
                            }
                        }
                        listener.onUsersLoaded(users)
                    },
                    { error ->
                        error.printStackTrace()
                    }
                )
                Volley.newRequestQueue(context).add(request)
            }
        }
   
        interface OnUsersLoadedListener {
            fun onUsersLoaded(users: List<UserModel>)
        }
    }
   

2. View:

    <!-- layout/user_item.xml -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
   
        <TextView
            android:id="@+id/textViewName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="18sp" />
   
        <TextView
            android:id="@+id/textViewEmail"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="16sp" />
    </LinearLayout>
   

3. Controller (Activity):

    class MainActivity : AppCompatActivity() {
        private lateinit var recyclerView: RecyclerView
        private lateinit var adapter: UserAdapter
   
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
   
            recyclerView = findViewById(R.id.recyclerView)
            recyclerView.layoutManager = LinearLayoutManager(this)
   
            // Fetch users using UserModel and Volley
            UserModel.fetchUsers(this, object : UserModel.OnUsersLoadedListener {
                override fun onUsersLoaded(users: List<UserModel>) {
                    // Update UI with fetched users
                    adapter = UserAdapter(users)
                    recyclerView.adapter = adapter
                }
            })
        }
    }
   

4. Adapter:

    class UserAdapter(private val users: List<UserModel>) :
        RecyclerView.Adapter<UserAdapter.ViewHolder>() {
   
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            val view = LayoutInflater.from(parent.context)
                .inflate(R.layout.user_item, parent, false)
            return ViewHolder(view)
        }
   
        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            val user = users[position]
            holder.textViewName.text = user.name
            holder.textViewEmail.text = user.email
        }
   
        override fun getItemCount(): Int {
            return users.size
        }
   
        class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
            val textViewName: TextView = itemView.findViewById(R.id.textViewName)
            val textViewEmail: TextView = itemView.findViewById(R.id.textViewEmail)
        }
    }
   

   In this example, the UserModel class serves as the model, responsible for fetching user data from the server using Volley. The MainActivity acts as the controller, initiating the network request and updating the view (RecyclerView) once the data is loaded. The UserAdapter class is responsible for binding user data to the RecyclerView. This example demonstrates how MVC and Volley can be used together to build a simple yet efficient Android app.

Okay devs, SO it's time to wrap up the blog. I hope you understand how the MVC Design pattern we used in our Project and How we use Volly lib for the API call. See you on the next Blog Devs.

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