Event Handler for LayerList widget item toggle in 4.9

Question

I can't quite grasp how to attach an event handler to the LayerList widget so that each time a user clicks (toggles) a layer, I can run a custom function. I want to attach this to every layer, not just individual ones... I tried const layerList = new LayerList({ view: mapView, container: 'layerlist' }); layerList.viewModel.on('trigger-action', myCustomFunction);‍‍‍‍‍‍‍‍‍‍ I also tried it with just layerList.on('trigger-action', myCustomFunction)‍ Any tips here?

VladS · Answer

RobertScheitlin__GISP,
this solution works for me, tnx. But listItemCreatedFunction removes item.panel.open switcher. Is it possible to keep the item.panel.open switcher and add an observer to it?

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I've found it!

Only add to defineActions next code:

item.panel = {
 content: 'legend',
 open: true,
};
item.panel.watch('open', function (event) {
  console.info(event);
});

rscheitlin · Answer

Strange the item.parent and uniqueParentItems was working for me.

Jay_Gregory · Answer

Okay, this kind of works for my purposes.  However, I've been having a hard time with the watch handlers.  Sometimes the function (in your example it's defineActions) runs 5 times for adding a single layer - and I haven't really been able to figure out how to only set a watcher once on the top level.  The uniqueParentItems doesn't always work - plus sometimes the item.title is "Layer" until the layer is actually loaded and able to get the title (since I'm loading layers from the portal).  It's making my head spin....