Share
Explore

Android Kotlin RecyclerView Lab

Last edited 178 days ago by Peter Sigurdson
Understanding the Purpose and Creation of Android Kotlin RecyclerView

Introduction


Welcome to today's lecture on Android Kotlin RecyclerView. In this session, we will discuss the purpose of RecyclerView, why it is essential in Android development, and how to create one using Kotlin. RecyclerView is a powerful UI component that significantly improves the performance and efficiency of displaying large datasets in your Android applications.

I. Purpose of Android Kotlin RecyclerView


Improved performance: RecyclerView efficiently reuses and recycles view items, reducing memory consumption and improving scrolling performance.
Enhanced user experience: By providing smooth scrolling and seamless data loading, RecyclerView offers a better user experience than traditional ListView or GridView.
Customizable layout: RecyclerView supports multiple layout managers, allowing you to create linear, grid, or staggered layouts with ease.
Separation of concerns: RecyclerView follows the ViewHolder pattern, separating data and view logic and making your code more maintainable.

II. Creating an Android Kotlin RecyclerView

Add RecyclerView to your project:

Include the RecyclerView dependency in your app's build.gradle file.
dependencies { implementation 'androidx.recyclerview:recyclerview:1.2.1' }

Define the data model:

Create a Kotlin data class representing the items you want to display in the RecyclerView.

Create a ViewHolder:
Define a ViewHolder class that extends RecyclerView.ViewHolder and initializes the view components.

Implement the RecyclerView.Adapter:

Create an Adapter class that extends RecyclerView.Adapter.
Implement the required methods:
onCreateViewHolder
onBindViewHolder
getItemCount

Set up the RecyclerView:

Add a RecyclerView to your activity or fragment layout XML file.
In your activity or fragment, initialize the RecyclerView, set its layout manager, and assign the adapter.

Conclusion

In this lecture, we have explored the purpose and creation of Android Kotlin RecyclerView.
RecyclerView is an essential tool for developers looking to create efficient, high-performing Android applications. By understanding its purpose and implementation, you can harness the power of RecyclerView to create outstanding user experiences in your applications. Keep practicing, and you'll become an expert in no time!

In this lab, we will create a simple Android application using Kotlin to display a list of hard-coded data using a RecyclerView.
We will cover the following topics:
Setting up the project
Creating the data model
Designing the layout
Creating the adapter and ViewHolder
Implementing the RecyclerView

1. Setting up the project


Open Android Studio and create a new project using the "Empty Activity" template.
Choose Kotlin as the programming language.
Name the project "RecyclerViewLab" and set the minimum SDK version to API 21: Android 5.0 (Lollipop).

2. Creating the data model

In the app/src/main/java folder of your project, create a new Kotlin data class file called "Person.kt".
Define the Person data class with two properties: name and age.

data class Person(val name: String, val age: Int)

3. Designing the layout

In the app/src/main/res/layout folder, open the "activity_main.xml" file.
Replace the default "Hello World" TextView with a RecyclerView widget.

<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

Create a new layout resource file called "person_item.xml" in the same folder.
Design the layout for a single person item, including a TextView for the name and another TextView for the age.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" android:padding="16dp">
<TextView android:id="@+id/nameTextView" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:textSize="16sp" />
<TextView android:id="@+id/ageTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="16sp" /></LinearLayout>

4. Creating the adapter and ViewHolder

In the app/src/main/java folder, create a new Kotlin file called "PersonAdapter.kt".
Define the PersonAdapter class that extends RecyclerView.Adapter<PersonAdapter.ViewHolder>.
Implement the required methods:
onCreateViewHolder,
onBindViewHolder, and
getItemCount.
Define the ViewHolder class that extends RecyclerView.ViewHolder.

import android.view.LayoutInflaterimport android.view.Viewimport android.view.ViewGroupimport android.widget.TextViewimport androidx.recyclerview.widget.RecyclerView
class PersonAdapter(private val personList: List<Person>) : RecyclerView.Adapter<PersonAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { val view = LayoutInflater.from(parent.context).inflate(R.layout.person_item, parent, false) return ViewHolder(view) }
override fun onBindViewHolder(holder: ViewHolder, position: Int) { val person = personList[position] holder.nameTextView.text = person.name holder.ageTextView.text = person.age.toString() }
override fun getItemCount(): Int { return personList.size }
class ViewHolder(view: View) : RecyclerView.ViewHolder(view) { val nameTextView: TextView = view.findViewById(R.id.nameTextView) val ageTextView: TextView = view.findViewById(R.id.ageTextView) }}


5. Implementing the RecyclerView


Open the "MainActivity.kt" file and import the necessary classes.
Inside the onCreate method, create a list of Person objects.
Initialize the RecyclerView with the PersonAdapter.


import androidx.appcompat.app.AppCompatActivityimport android.os.Bundleimport androidx.recyclerview.widget.RecyclerView
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main)
val personList = listOf( Person("John Doe", 30), Person("Jane Smith", 25), Person("Alice Johnson", 23), Person("Bob Brown", 33) )
val recyclerView: RecyclerView = findViewById(R.id.recyclerView) recyclerView.adapter = PersonAdapter(personList) }}

Now, run the application, and you should see the hard-coded data displayed in a RecyclerView.
This lab should give you a basic understanding of how to display data in a RecyclerView using Kotlin, create custom adapters and ViewHolders, and work with hard-coded data.
Want to print your doc?
This is not the way.
Try clicking the ⋯ next to your doc name or using a keyboard shortcut (
CtrlP
) instead.