Cluster Renderer for Google Map

ClusterRender.kt

class ClusterRender(
    private val context: Context,
    map: GoogleMap,
    clusterManager: ClusterManager<MapClusterItem>
) : DefaultClusterRenderer<MapClusterItem>(context, map, clusterManager) {
    private val factory: IconGenerator = IconGenerator(context)
    private var selectedPinColor = -1
    private var unselectedPinColor = -1

    private var currentZoomLevel = -1f

    init {
        this.minClusterSize = MIN_CLUSTER_SIZE
        selectedPinColor = ContextCompat.getColor(context, R.color.colorSelectedPin)
        unselectedPinColor = ContextCompat.getColor(context, R.color.colorBlue)
    }

    override fun onBeforeClusterItemRendered(
        clusterItem: MapClusterItem?,
        markerOptions: MarkerOptions?
    ) {
        if (clusterItem != null && markerOptions != null) {
            markerOptions?.apply {
                icon(null)

                factory.setTextAppearance(context, R.style.TextAppearanceWhiteOnMap)
                if (clusterItem?.isSelected) {
                    factory.setColor(selectedPinColor)
                } else {
                    factory.setColor(unselectedPinColor)
                }

                anchor(factory.anchorU, factory.anchorV)
                position(clusterItem?.position)
            }
        }

        super.onBeforeClusterItemRendered(clusterItem, markerOptions)
    }

    override fun onClusterItemRendered(clusterItem: MapClusterItem?, marker: Marker?) {
        marker?.let {
            it.setIcon(null)
            // TODO: track changes, it may crash at marker.setIcon() even with null checks
            // https://github.com/googlemaps/android-maps-utils/issues/63
            // Workaround --> UPDATE: not helpful
            if (marker.tag == null) {
                marker.tag = MARKER_TAG
            }
        }

        onClusterItemChange(clusterItem, marker)

        super.onClusterItemRendered(clusterItem, marker)
    }

    override fun shouldRenderAsCluster(cluster: Cluster<MapClusterItem>?): Boolean {
       val isZoomLevelSuites = currentZoomLevel < MAX_ZOOM_LVL - POINT_ZOOM_LVL
       return super.shouldRenderAsCluster(cluster) && isZoomLevelSuites
    }

    override fun getColor(clusterSize: Int): Int {
        return ContextCompat.getColor(context, R.color.colorBlue)
    }

    fun setCurrentZoomLevel(zoomLevel: Float) {
        currentZoomLevel = zoomLevel
    }

    fun onClusterItemChange(clusterItem: MapClusterItem?, marker: Marker?) {
        if (clusterItem != null && marker != null) {
            factory.setTextAppearance(context, R.style.TextAppearanceWhiteOnMap)
            if (clusterItem?.isSelected) {
                factory.setColor(selectedPinColor)
            } else {
                factory.setColor(unselectedPinColor)
            }
			
            marker?.title = clusterItem?.title
            if (marker?.tag != null) {
                marker?.setIcon(BitmapDescriptorFactory.fromBitmap(factory.makeIcon("${marker?.title}")))
            }
        }
    }

    companion object {
        const val DOT_ZOOM_LVL = 1.5f
        const val POINT_ZOOM_LVL = 3f
        const val MIN_CLUSTER_SIZE = 4
        const val MARKER_TAG = "marker-tag"
    }
}