How to create a Carousel in Android using Kotlin

Last updated on: September 7, 2022

In this tutorial, I’m going to show you how to create a carousel (+ zoom-in effect) using the newer ViewPager library the ViewPager2.

Adding library

Go to your app-level gradle.build file, and add the following dependency:

dependencies { // ... implementation 'androidx.viewpager2:viewpager2:1.0.0' // ... }
Code language: Kotlin (kotlin)

Adding Carousel in XML

In the main_activity.xml file, we add a ViewPager2 and set its parent view to have android:clipChildren="false" and android:clipToPadding="false" so that we can see the left and right carousel items outside the bounds of the viewpager.

<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" <!-- ... --> android:clipChildren="false" android:clipToPadding="false"> <!-- Toolbar...--> <androidx.viewpager2.widget.ViewPager2 android:id="@+id/view_pager" android:layout_width="280dp" android:layout_height="260dp" <!--Layout Constraints...--> /> </androidx.constraintlayout.widget.ConstraintLayout>
Code language: Swift (swift)
Adding the ViewPager2 for the carousel

Creating Carousel Item in XML

Now, it’s time to create the carousel item.

We create a new Layout Resource File by going right-click on the layout folder > New > Layout Resource File

Creating the carousel item layout

We give the name item_carousel and press OK

Naming the carousel item layout

And we add the following code inside:

<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/card_background" android:elevation="8dp"> <!-- You must give a background to this layout if you want the shadow to work --> <TextView android:id="@+id/textview" android:layout_width="match_parent" android:layout_height="0dp" android:gravity="center" android:padding="20dp" android:text="Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus sit amet lectus a mi lobortis iaculis. Mauris odio tortor, accumsan vel gravida sit amet, malesuada a tortor. Cras mattis augue eget dolor vestibulum, id euismod diam rutrum." android:textAlignment="center" android:textColor="@android:color/white" android:textSize="20sp" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>
Code language: HTML, XML (xml)

Note: We use match_parent for layout_width and layout_height because ViewPager2 doesn’t allow the viewpager items to have a certain width and height. That’s why we set a width and height to the ViewPager2 at the main_activity.xml

How the carousel item looks like at the end

Creating the Adapter

ViewPager2 is using a RecyclerView adapter, so it’s the same as when we use one in a RecyclerView.

Because of that, we’re not going to explain what we have in the adapter. We’re only going to create the file and paste the code inside.

We right-click on the project folder > New > Kotlin Class/File, we select Class and we give the name CarouselRVAdapter

Creating the RecyclerView Adapter for the Carousel
Naming the RecyclerView Adapter for the Carousel

And inside the file we paste:

class CarouselRVAdapter(private val carouselDataList: ArrayList<String>) : RecyclerView.Adapter<CarouselRVAdapter.CarouselItemViewHolder>() { class CarouselItemViewHolder(view: View) : RecyclerView.ViewHolder(view) override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CarouselItemViewHolder { val viewHolder = LayoutInflater.from(parent.context).inflate(R.layout.item_carousel, parent, false) return CarouselItemViewHolder(viewHolder) } override fun onBindViewHolder(holder: CarouselItemViewHolder, position: Int) { val textView = holder.itemView.findViewById<TextView>(R.id.textview) textView.text = carouselDataList[position] } override fun getItemCount(): Int { return carouselDataList.size } }
Code language: Kotlin (kotlin)

Creating Carousel

Now, we go to the MainActivity.kt file, and apply these steps to the viewPager:

1) Don’t clip items left and right.
2) Don’t clip the padding to allow full width.
3) Render the left and right items.
4) Remove the effect when you’re scrolling to the edge.

class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val viewPager = findViewById<ViewPager2>(R.id.view_pager) viewPager.apply { clipChildren = false // No clipping the left and right items clipToPadding = false // Show the viewpager in full width without clipping the padding offscreenPageLimit = 3 // Render the left and right items (getChildAt(0) as RecyclerView).overScrollMode = RecyclerView.OVER_SCROLL_NEVER // Remove the scroll effect } // ... } }
Code language: Kotlin (kotlin)

After that, we create and pass the data to the adapter

class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val viewPager = findViewById<ViewPager2>(R.id.view_pager) // ... val demoData = arrayListOf( "Curabitur sit amet rutrum enim, sit amet commodo urna. Nullam nec nisl eget purus vulputate ultrices nec sit amet est. Sed sodales maximus risus sit amet placerat.", "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus sit amet lectus a mi lobortis iaculis. Mauris odio tortor, accumsan vel gravida sit amet, malesuada a tortor.", "Praesent efficitur eleifend eros quis elementum. Vivamus eget nunc ante. Sed sed sodales libero. Nam ipsum lorem, consequat at ipsum sit amet, tempor vulputate nibh.", "Aliquam sodales imperdiet augue at consectetur. Suspendisse dui mauris, tincidunt non auctor quis, facilisis et tellus.", "Ut non tincidunt neque, et sodales ligula. Quisque interdum in dui sit amet sagittis. Curabitur erat magna, maximus quis libero quis, dapibus eleifend orci." ) viewPager.adapter = CarouselRVAdapter(demoData) // ... } }
Code language: Kotlin (kotlin)

Adding Spacing

We use the MarginPageTransformer() class to add some space between the carousel items.

In this example we use 40dp.

Note: Because MarginPageTransformer uses pixels as a input value, we put the value in dp and multiply it by the display’s density to convert it into pixels.

class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val viewPager = findViewById<ViewPager2>(R.id.view_pager) //... val compositePageTransformer = CompositePageTransformer() compositePageTransformer.addTransformer(MarginPageTransformer((40 * Resources.getSystem().displayMetrics.density).toInt())) viewPager.setPageTransformer(compositePageTransformer) } }
Code language: Kotlin (kotlin)

Adding Scaling (Zoom-in) Effect

If you want the carousel item that you see in the center to zoom in, or scale up, add this transformer before setting the PageTransformer:

class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val viewPager = findViewById<ViewPager2>(R.id.view_pager) // ... val compositePageTransformer = CompositePageTransformer() compositePageTransformer.addTransformer(MarginPageTransformer((40 * Resources.getSystem().displayMetrics.density).toInt())) compositePageTransformer.addTransformer { page, position -> val r = 1 - abs(position) page.scaleY = (0.80f + r * 0.20f) } viewPager.setPageTransformer(compositePageTransformer) } }
Code language: Kotlin (kotlin)
You can find the final project here

If you have any questionsplease feel free to leave a comment below

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