draggable2D

Modifier in Compose Foundation

Configure touch dragging for the UI element in both orientations. The drag distance reported to [Draggable2DState], allowing users to react to the drag delta and update their state.

The common common usecase for this component is when you need to be able to drag something inside the component on the screen and represent this state via one float value

If you are implementing dragging in a single orientation, consider using [draggable].

Last updated: 2024-10-22 13:47

Installation

dependencies {
   implementation("androidx.compose.foundation:foundation:1.8.0-alpha04")
}

Overloads

@Stable
fun Modifier.draggable2D(
    state: Draggable2DState,
    enabled: Boolean = true,
    interactionSource: MutableInteractionSource? = null,
    startDragImmediately: Boolean = false,
    onDragStarted: (startedPosition: Offset) -> Unit = NoOpOnDragStart,
    onDragStopped: (velocity: Velocity) -> Unit = NoOpOnDragStop,
    reverseDirection: Boolean = false
): Modifier

Parameters

name	description
state	[Draggable2DState] state of the draggable2D. Defines how drag events will be interpreted by the user land logic.
enabled	whether or not drag is enabled
interactionSource	[MutableInteractionSource] that will be used to emit [DragInteraction.Start] when this draggable is being dragged.
startDragImmediately	when set to true, draggable2D will start dragging immediately and prevent other gesture detectors from reacting to "down" events (in order to block composed press-based gestures). This is intended to allow end users to "catch" an animating widget by pressing on it. It's useful to set it when value you're dragging is settling / animating.
onDragStarted	callback that will be invoked when drag is about to start at the starting position, allowing user to perform preparation for drag.
onDragStopped	callback that will be invoked when drag is finished, allowing the user to react on velocity and process it.
reverseDirection	reverse the direction of the dragging, so top to bottom dragging will behave like bottom to top and left to right will behave like right to left.

Code Example

Draggable2DSample

@Composable
fun Draggable2DSample() {
    // Draw a box that has a a grey background
    // with a red square that moves along 300.dp dragging in both directions
    val max = 200.dp
    val min = 0.dp
    val (minPx, maxPx) = with(LocalDensity.current) { min.toPx() to max.toPx() }
    // this is the offset we will update while dragging
    var offsetPositionX by remember { mutableStateOf(0f) }
    var offsetPositionY by remember { mutableStateOf(0f) }

    Box(
        modifier =
            Modifier.width(max)
                .height(max)
                .draggable2D(
                    state =
                        rememberDraggable2DState { delta ->
                            val newValueX = offsetPositionX + delta.x
                            val newValueY = offsetPositionY + delta.y
                            offsetPositionX = newValueX.coerceIn(minPx, maxPx)
                            offsetPositionY = newValueY.coerceIn(minPx, maxPx)
                        }
                )
                .background(Color.LightGray)
    ) {
        Box(
            Modifier.offset {
                    IntOffset(offsetPositionX.roundToInt(), offsetPositionY.roundToInt())
                }
                .size(50.dp)
                .background(Color.Red)
        )
    }
}