Some clusters do not transform into markers when clustering condition is based on map zoom level

[tomsaju]

Summary

I used this library for clustering a set of points in google map. The requirement is such that clustering is based only on zoom level. On max zoom in , all items are unclustered and markers should be shown. But in some cases, the markers are not visible even on maximum zoom in.(Please note that on max zoom out even single markers are displayed as cluster with text 1)

Expected behavior

On tapping cluster(or zooming in manually) with single item, it should zoom in and turn into marker

Observed behavior

Map zoomed in, but cluster remained same. did not showed marker

Environment details

1. Device make and model, or emulator details - Vivo 1723 (and multiple other devices)
2. Android version - 8.1.0
3. Library version and other environment information - Library version 2.0.3

Steps to reproduce

This can be reproduced using the demo app by making minor changes to CustomMarkerClusteringDemoActivity.
(I am minimizing the customization here)

1. Add a Cluster Renderer to the activity with zoom based clustering condition and also a camera listener to get map zoom level

private class ZoomBasedRenderer extends DefaultClusterRenderer<Person> implements GoogleMap.OnCameraMoveListener{
        private Float mapZoomLevel = 15f;
        public ZoomBasedRenderer(Context context, GoogleMap map, ClusterManager<Person> clusterManager) {
            super(context, map, clusterManager);
        }

        @Override
        public void onCameraMove() {
            //map zoom level gets updated here on camera change
            mapZoomLevel =  getMap().getCameraPosition().zoom;
        }

        @Override
        protected boolean shouldRenderAsCluster(@NonNull Cluster<Person> cluster) {
         //cluster when mapZoomLevel is less than 12f. Else show as marker    
         return mapZoomLevel<12f;
        }
    }

2. Initialise cluster manager by changing the startDemo(boolean isRestore)

@Override
    protected void startDemo(boolean isRestore) {
       //point camera to desired location 
       if (!isRestore) {
            getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(18.550931, 74.115642), 9.5f));
        }

        mClusterManager = new ClusterManager<>(this, getMap());
        //set max distance to form a single cluster country wise on max zoom out
        mClusterManager.getAlgorithm().setMaxDistanceBetweenClusteredItems(300);
        
        //initialise renderer
        ZoomBasedRenderer renderer = new ZoomBasedRenderer(this,getMap(),mClusterManager);
        mClusterManager.setRenderer(renderer);
        getMap().setOnCameraIdleListener(mClusterManager);
        getMap().setOnMarkerClickListener(mClusterManager);
        getMap().setOnInfoWindowClickListener(mClusterManager);
        
        //set camera listener inside renderer
        getMap().setOnCameraMoveListener(renderer);
        mClusterManager.setOnClusterClickListener(this);
        mClusterManager.setOnClusterInfoWindowClickListener(this);
        mClusterManager.setOnClusterItemClickListener(this);
        mClusterManager.setOnClusterItemInfoWindowClickListener(this);

        addItems();
        mClusterManager.cluster();
    }

3)Modify AddItems() to return only two points. (I am returning two example points that this issue occur)

     private void addItems() {
        mClusterManager.addItem(new Person(new LatLng(18.528146, 73.797726), "Loc1", R.drawable.walter));

       
        mClusterManager.addItem(new Person(new LatLng(18.545723, 73.917202), "Loc2", R.drawable.gran));

    }

[nenick]

I have the same issue. I found that the GridBasedAlgorithm and the default new ScreenBasedAlgorithmAdapter<>(new PreCachingAlgorithmDecorator<>(new NonHierarchicalDistanceBasedAlgorithm<T>())); behave differently.

With default NonHierarchicalDistanceBasedAlgorithm it stops calling shouldRenderAsCluster() after a certain zoom level (~11) when it was already called once. For zoom levels 1-11 this method is regularly called when you perform zoom actions. Above the zoom level 11 this method will be called once and then never again, until you zoom level is again below 11.
When there are two marks nearby, the behaviour does change and clustering works fine.

With the GridBasedAlgorithm the shouldRenderAsCluster() gets also called regularly when zoom level is above 11.

So the question is, how can we adjust that behaviour from the NonHierarchicalDistanceBasedAlgorithm?

Edit:
I found a dirty quick fix. Looks like the algorithm switch changed the behaviour but wasn't the root cause. The issue is an optimization in the DefaultClusterRenderer class to avoid unnecessary rendering if the clusters didn't change.

For the fix you have to reimplement (copy/paste) the DefaultClusterRenderer and disable the first lines from the run method in the inner RenderTask class.

public class DefaultClusterRenderer <T extends ClusterItem> implements ClusterRenderer<T> {
    ...
    private class RenderTask implements Runnable {private class RenderTask implements Runnable {
        ...
        public void run() {
            // as dirty quick fix disable these lines
            if (clusters.equals(DefaultClusterRenderer.this.mClusters)) {
                 mCallback.run();
                 return;
            }

[Program8]

I am also facing same issue . Library version is 2.2.0

[amatkivskiy]

Also having the same issue 😞

[barbeau]

I've confirmed that I can reproduce this issue in this branch:
https://github.com/googlemaps/android-maps-utils/tree/sean/test-774-zoom-cluster

I can also confirm that commenting out the below lines in DefaultClusterRenderer.RenderTask.run() as discussed in #774 (comment) does force correct behavior:

        @SuppressLint("NewApi")
        public void run() {
            // Commenting out these lines forces correct behavior
//            if (clusters.equals(DefaultClusterRenderer.this.mClusters)) {
//                mCallback.run();
//                return;
//            }

            final MarkerModifier markerModifier = new MarkerModifier();

[NizarETH]

Also having the same issue shouldRenderAsCluster() not working in all zoom levels.

[barbeau]

Hi all! I've opened a pull request here that should hopefully address this use case - #996.

[googlemaps-bot]

🎉 This issue has been resolved in version 2.3.0 🎉

The release is available on:

• v2.3.0
• GitHub release

Your semantic-release bot 📦🚀