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MarkerState encapsulation
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import androidx.compose.runtime.* | |
import com.google.android.gms.maps.model.LatLng | |
import com.google.maps.android.compose.DragState.* | |
import com.google.maps.android.compose.GoogleMapComposable | |
import com.google.maps.android.compose.Marker | |
import com.google.maps.android.compose.MarkerState | |
import kotlinx.coroutines.flow.onCompletion | |
@Immutable | |
interface DragOps { | |
fun onMove(position: LatLng) | |
fun onCancel() | |
fun onEnd() | |
} | |
@Composable | |
@GoogleMapComposable | |
fun Marker( | |
modelPosition: LatLng, | |
draggable: Boolean, | |
/* ... */ | |
onDrag: ((LatLng) -> Unit) -> DragOps | |
) { | |
val markerState: MarkerState = remember { MarkerState() } | |
Marker( | |
markerState, | |
draggable = draggable, | |
/* ... */ | |
) | |
var dragOps: DragOps? by remember { mutableStateOf(null) } | |
// Sync marker state to model if model position changed without dragging; | |
// if model position simply aligns with markerState nothing happens | |
LaunchedEffect(modelPosition) { | |
if (dragOps == null) markerState.position = modelPosition | |
} | |
val currentOnDrag: ((LatLng) -> Unit) -> DragOps by rememberUpdatedState(onDrag) | |
// Naive dragging observer that would not work reliably currently | |
LaunchedEffect(Unit) { | |
snapshotFlow { markerState.dragState to markerState.position } | |
.onCompletion { | |
dragOps?.let { | |
dragOps = null | |
it.onCancel() | |
} | |
} | |
.collect { (dragState, position) -> | |
when (dragState) { | |
START -> { | |
dragOps = currentOnDrag { markerState.position = it } | |
dragOps!!.onMove(position) | |
} | |
DRAG -> dragOps!!.onMove(position) | |
END -> { | |
dragOps!!.let { | |
it.onMove(position) | |
dragOps = null | |
it.onEnd() | |
} | |
} | |
} | |
} | |
} | |
} |
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