How to Create ViewPager Transformation in Jetpack Compose?

Getting Started with ViewPagerTransformation in Jetpack Compose

Before we dive into the implementation, make sure you have the following prerequisites:

• JDK 11 or higher
• Android Studio 4.2 or higher
• Jetpack Compose 1.0.0 or higher

Step 1: Add Jetpack Compose to Your Project

If you haven’t already, add Jetpack Compose to your project by adding the following lines to your `build.gradle` file:

dependencies {
  implementation 'androidx.compose.ui:ui-tooling:1.0.0'
  implementation 'androidx.compose.foundation:foundation:1.0.0'
  implementation 'androidx.compose.material:material:1.0.0'
}

Step 2: Create a ViewPager Composable

Create a new composable function that will serve as your ViewPager:

@Composable
fun ViewPager() {
  // We'll implement the ViewPager logic here
}

Step 3: Define Your Pages

Define the pages that will be part of your ViewPager. For this example, we’ll create two simple pages:

@Composable
fun Page1() {
  Text("Page 1")
}

@Composable
fun Page2() {
  Text("Page 2")
}

Implementing ViewPagerTransformation in Jetpack Compose

Now, let’s get to the meat of the matter. We’ll create a ViewPagerTransformation that will animate between our two pages.

@Composable
fun ViewPagerTransformation(pagerState: PagerState) {
  val pageWidth = 300.dp
  val transformer = ViewPagerTransformer(
    pageWidth = pageWidth,
    orientation = Orientation.Horizontal
  )

  LazyRow(
    modifier = Modifier
      .width(pageWidth)
      .height(200.dp),
    state = pagerState,
    transformer = transformer
  ) {
    item { Page1() }
    item { Page2() }
  }
}

Understanding the Code

Let’s break down the code:

• PagerState is a state object that keeps track of the current page and its offset.
• ViewPagerTransformer is a class that defines the transformation logic. We’ve set the page width to 300dp and the orientation to horizontal.
• LazyRow is a composable function that lays out its children in a horizontal row. We’ve set the modifier to constrain the width and height of the row.
• We’ve added two items to the row: Page1 and Page2.

Adding Animation to the ViewPagerTransformation

To add animation to our ViewPagerTransformation, we’ll use Compose’s built-in animation APIs:

@Composable
fun ViewPagerTransformation(pagerState: PagerState) {
  val pageWidth = 300.dp
  val transformer = ViewPagerTransformer(
    pageWidth = pageWidth,
    orientation = Orientation.Horizontal
  )

  val animationSpec = tween(durationMillis = 500, easing = LinearEasing)

  LazyRow(
    modifier = Modifier
      .width(pageWidth)
      .height(200.dp),
    state = pagerState,
    transformer = transformer
  ) {
    items(pagerState.pages) { page ->
      val offset = pagerState.calculatePageOffset(page)
      val animatedOffset by remember { mutableStateOf(0f) }

      LaunchedEffect(offset) {
        animatedOffset.animateTo(offset, animationSpec)
      }

      Box(
        modifier = Modifier
          .width(pageWidth)
          .height(200.dp)
          .offset(x = animatedOffset.dp)
      ) {
        when (page) {
          0 -> Page1()
          1 -> Page2()
        }
      }
    }
  }
}

Rounding Up the Edges

To complete the ViewPagerTransformation, let’s add a custom edge effect to our pager:

@Composable
fun ViewPagerTransformation(pagerState: PagerState) {
  // ...

  LazyRow(
    // ...
  ) {
    items(pagerState.pages) { page ->
      // ...

      Box(
        modifier = Modifier
          .width(pageWidth)
          .height(200.dp)
          .offset(x = animatedOffset.dp)
          .clip(RoundedCornerShape(16.dp))
      ) {
        // ...
      }
    }
  }
}

Conclusion

And that’s it! You’ve successfully created a ViewPagerTransformation in Jetpack Compose. With this comprehensive guide, you should now have a solid understanding of how to create custom transformations and animations in your Android app.

What’s Next?

Now that you’ve mastered ViewPagerTransformation, why not take it to the next level by:

• Experimenting with different animation curves and timing
• Adding more complex edge effects and clipping
• Creating a custom ViewPager indicator

The possibilities are endless, and with Jetpack Compose, the sky’s the limit!

Frequently Asked Question

Get ready to elevate your Jetpack Compose skills and learn how to create a stunning ViewPager transformation!