Physics Layout

This library offsers a dyn4j wrapper for Jetpack Compose.

🚧 Experimental 🚧

Before reaching version 1.0, this library is considered experimental, which means that there is no guaranteed backwards compatibility between versions. Signatures, interfaces, names, etc. may and will most likely change.

Sample App

physics.mov

Download

dependencies {
    implementation 'io.github.klassenkonstantin:physics-layout:<version>'
}

How to use

To get started, create a PhysicsLayout and fill it with Composables. Every root level Composable in PhysicsLayout must use the body modifier to tell the simulation how the Composable should behave in the physics world. The body modifier can be configured with following parameters:

• id: The id the body should have in the simulation. Useful for operations that act directly on bodies (not yet supported).
• shape: Describes the outer bounds of the body. Only RoundedCornerShapes are supported.
• isStatic: Set true for unmovable bodies like walls and floors.
• initialTranslation: Where this body should be placed in the layout. An Offset of (0,0) is the center of the layout, not top left.
• initialImpulse: The impulse that should be applied to this body once it's placed into the world
• dragConfig: Set to DragConfig.Draggable to enable drag support

PhysicsLayout takes a Simulation as a parameter. Use rememberSimulation to create a Simulation. rememberSimulation is used as the default argument for simulation.

Example usage

PhysicsLayout {
    Card(
        modifier = Modifier.body(
            shape = CircleShape,
        ),
        shape = CircleShape,
    ) {
        Icon(
            modifier = Modifier
                .size(32.dp)
                .padding(4.dp),
            imageVector = Icons.Default.Star,
            contentDescription = "Star",
            tint = Color.White
        )
    }
}

This would add a ball with a star in the center of the layout, which then starts falling to the ground.

Note: The shape must be set on both the body modifier and the Card.

Change gravity

If you need to change the gravity of the simulated world, use Simulation.setGravity

Caveats, notes, missing features

• I don't think Compose was made to display hundrets of Composables at the same time. So maybe it's not a good idea to build a particle system out of this.
• In general, what is true for all of Compose is especially true for this Layout: Release builds perform way better than debug builds.
• State is not restored on config changes 😱.
• Currently there is no way to observe bodies / collosions / etc.