Runtime type checking contradicts compile time type declarations

Question

In trying to circumvent another problem I tried creating a FeatureLayer via its FeatureLayer(FeatureTable) constructor. FeatureCollectionTable is a subclass of FeatureTable and yet passing one as the argument to the above constructor results in an exception being thrown. Why?

"Cannot create a feature layer from a feature collection table. Add the feature collection table to a feature collection."

DaveWhitla · Answer

Thanks for the code suggestion. I already solved the issue using the code I provided above. I am not loading anything asynchronously - the table is populated locally.

Does simply adding a layer to the map's operationalLayers list trigger doneLoadingListeners if the layer is backed by a FeatureCollectionTable rather than a service call? If I had known that I might have tried it first, but honestly I think that listening for subLayerContents changes better reflects my aim as it will catch subsequent layer additions - if that is possible.

DaveWhitla · Answer

This isn’t the issue I’m afraid. The bug in your code is definitely timing sensitive as I could only reproduce it sometimes. Under no circumstances should Iterator.hasNext() return true and the next call to Iterator.next() throw an index out of bounds exception.

MarkBaird · Answer

I suspect the issue you have been seeing is that your application is trying to access resources before they are loaded.  In the Runtime SDK we encourage asynchronous development techniques to ensure that you don't write any code which potentially blocks the UI thread of your app.  I'd have a look at this page on loadable resources.

In your code above I suspect something in your app has triggered a load event because the ListChangesListener has triggered.  This may have been caused by you adding the layer to the map, or you called LoadAsync on the layer.

Anyway I've added a snipped of code to set the labelling property within a doneLoadListener.  If you call this outside of the listener it throws an error.

featureCollectionLayer.loadAsync(); // needed if you didn't add it to a map.
      featureCollectionLayer.addDoneLoadingListener(()-> {
        System.out.println("loaded");
        // if this is called without the layer loaded it will fail.
        featureCollectionLayer.getLayers().get(0).setLabelsEnabled(false);
      });

This might be same issue with your other post.

Let me know if this helps.