Exploring Motion Layout in Jetpack Compose: Creating Smooth Animations with Ease

Part of the series "Android Development Series by Mircea Ioan Soit"

Animations play a crucial role in enhancing the user experience by providing visual feedback and creating engaging transitions. Jetpack Compose offers a variety of ways to animate components, but the real power comes with Motion Layout. Originating from XML-based Android development, Motion Layout has now entered the world of Compose through an experimental API, giving developers granular control over animations and transitions.

In this article, we'll dive into how to work with Motion Layout in Jetpack Compose and create smooth, responsive animations that take your app’s UX to the next level.

1. Introduction to Motion Layout

Motion Layout is part of the ConstraintLayout family and is primarily designed for creating complex animations between different states of UI components. Unlike simpler animation APIs, Motion Layout allows you to control the motion of multiple elements simultaneously, orchestrating transitions based on user input or programmatic triggers.

Motion Layout in Jetpack Compose is experimental but evolving rapidly. It gives developers access to sophisticated animation systems while maintaining the declarative style of Compose.

2. Setting Up Motion Layout in Jetpack Compose

Before diving into the code, it’s important to understand the basics of Motion Layout in Compose. As of now, you can use ConstraintLayout and MotionScene composables to define layouts and animations.

Here’s a simple example to get started:

import androidx.constraintlayout.compose.MotionLayout
import androidx.constraintlayout.compose.MotionScene
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.size
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

@Composable
fun SimpleMotionLayout() {
    MotionLayout(
        motionScene = MotionScene(
            """
                {
                  ConstraintSets: {
                    start: {
                      box: {
                        width: 100, height: 100,
                        start: ['parent', 'start', 16],
                        top: ['parent', 'top', 16]
                      }
                    },
                    end: {
                      box: {
                        width: 100, height: 100,
                        end: ['parent', 'end', 16],
                        bottom: ['parent', 'bottom', 16]
                      }
                    }
                  },
                  Transitions: {
                    default: {
                      from: 'start',
                      to: 'end',
                      pathMotionArc: 'startVertical'
                    }
                  }
                }
            """
        ),
        progress = 0.5f,  // Halfway through the animation
        modifier = Modifier.size(300.dp)
    ) {
        Box(
            modifier = Modifier
                .layoutId("box")
                .background(Color.Red)
        )
    }
}        

3. Understanding MotionScene in Compose

In the above example, the MotionScene composable defines the animation states and transitions between them. It uses two core concepts:

• ConstraintSets: These define the layout constraints of UI elements at the start and end states of the animation.
• Transitions: These describe how the UI elements move between the start and end states.

The progress property in MotionLayout controls the animation, with 0.0 representing the start state and 1.0 the end state. A value of 0.5, as used in the example, places the layout exactly halfway through the transition.

4. Creating More Complex Animations

Motion Layout’s power becomes apparent when you create more complex animations that involve multiple UI elements moving in different ways. Let’s look at how to animate two boxes along different paths simultaneously.

@Composable
fun ComplexMotionLayout() {
    MotionLayout(
        motionScene = MotionScene(
            """
                {
                  ConstraintSets: {
                    start: {
                      box1: {
                        width: 100, height: 100,
                        start: ['parent', 'start', 16],
                        top: ['parent', 'top', 16]
                      },
                      box2: {
                        width: 100, height: 100,
                        start: ['parent', 'end', 16],
                        top: ['parent', 'bottom', 16]
                      }
                    },
                    end: {
                      box1: {
                        width: 100, height: 100,
                        end: ['parent', 'end', 16],
                        bottom: ['parent', 'bottom', 16]
                      },
                      box2: {
                        width: 100, height: 100,
                        start: ['parent', 'start', 16],
                        bottom: ['parent', 'top', 16]
                      }
                    }
                  },
                  Transitions: {
                    default: {
                      from: 'start',
                      to: 'end',
                      pathMotionArc: 'startVertical'
                    }
                  }
                }
            """
        ),
        progress = 0.75f,  // Three quarters through the animation
        modifier = Modifier.size(400.dp)
    ) {
        Box(
            modifier = Modifier
                .layoutId("box1")
                .background(Color.Blue)
        )
        Box(
            modifier = Modifier
                .layoutId("box2")
                .background(Color.Green)
        )
    }
}        

In this example, two boxes (box1 and box2) follow separate paths as they transition from the start to the end states. The result is a coordinated, multi-element animation, with the progress controlled by the progress property.

5. Animating Based on User Input

A key feature of Motion Layout is its ability to respond to user interactions, such as dragging or swiping. You can control animations dynamically based on touch events, making your app feel more responsive and interactive.

Let’s add a slider to control the progress of our animation:

import androidx.compose.foundation.layout.Column
import androidx.compose.material.Slider
import androidx.compose.runtime.*
import androidx.compose.ui.tooling.preview.Preview

@Composable
fun MotionWithSlider() {
    var progress by remember { mutableStateOf(0f) }

    Column {
        SimpleMotionLayout(progress = progress)
        Slider(
            value = progress,
            onValueChange = { progress = it }
        )
    }
}        

The Slider in this example allows the user to control the animation progress manually, adding an interactive element to the UI.

6. Best Practices for Working with Motion Layout

• Optimize Performance: Use motion layouts only for complex animations. For simpler transitions, prefer lighter animation tools such as animateDpAsState or animateFloatAsState.
• Test Across Devices: Ensure that your motion-based animations look and behave as expected across different screen sizes and orientations.
• Smooth Transitions: Adjust the duration of transitions and use easing curves (easing: "easeInOut") for smoother animations that feel natural.

7. Use Cases for Motion Layout

Motion Layout is perfect for creating complex, high-quality animations in apps that require fine control over UI transitions. Some common use cases include:

• Animated onboarding flows, where multiple elements move in synchronization.
• Responsive swipe gestures, such as swiping between pages or dismissing elements.
• Menu expansions and collapses, where components rearrange dynamically.
• Complex loading indicators, involving multiple moving parts.

8. Conclusion: Unlocking the Power of Motion Layout

Motion Layout in Jetpack Compose offers Android developers a powerful tool to create intricate animations and transitions. While still in its experimental stage, it provides extensive capabilities for animating multiple elements and creating responsive UI interactions. As Jetpack Compose continues to evolve, Motion Layout will likely become a staple for developers who want complete control over UI animations.