GoogleMap onCameraIdle event not firing
<p>I'm trying to clustering the markers on google map because there's too many markers on the map (approximately 6000+ markers).</p>

<p>So I googled and found some documentations about marker clustering and I apply it to my source code, but markers are not shown in google map.</p>

<p>Partial source code of <code>FragMap</code> fragment.
</p>

<pre><code>@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    SupportMapFragment map = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.display_map);
    if (map == null) {
        Log.e(Tag, "Google Map fragment(id: display_map) is null reference!");
        return;
    }

    map.getMapAsync(this);
}

@Override
public void onMapReady(GoogleMap googleMap) {
    if (DataPackage.getEQMarkerManager() == null) {
        if (!DataPackage.initializeEQMarkerManager(getActivity(), googleMap)) {
            Log.w(Tag, "EQMarkerManager initialization failure");
        }
    }
}
</code></pre>

<p>and partial source code of <code>EQMarkerManager</code> and it's implements <code>GoogleMap.OnCameraIdleListener</code> interface.
</p>

<pre><code>public EQMarkerManager(Context ctx, GoogleMap map) {
    // ...
    clusterManager = new ClusterManager&lt;&gt;(ctx, map);
    clusterManager.setRenderer(new EQRenderer&lt;&gt;(ctx, map, clusterManager));

    map.setOnCameraIdleListener(this);

    clusterManager.addItems(markers);
}

@Override
public void onCameraIdle() {
    Log.d(Tag, "onCameraIdle");
}
</code></pre>

<p>but <code>onCameraIdle</code> callback was never called. Why OnCameraIdle event is not firing? </p>

<p>gradle:</p>

<pre><code>compile 'com.google.android.gms:play-services-maps:9.8.0'
compile 'com.google.maps.android:android-maps-utils:0.4.4+'
</code></pre>

<p>Tested on Marshmallow device (SDK version 23).</p>

<p><strong>ADDED</strong>: What is the meaning of <code>+</code> on gradle compile?</p>