topic Re: Layerlist selected item becomes visible watch in ArcGIS JavaScript Maps SDK Questions

Layerlist selected item becomes visible watch

GregoryBologna — Tue, 29 Oct 2024 18:18:26 GMT

I have visibility watches on a layerList, but I cannot get the watches to hit on the items in the layerList when an item is selected. I want to get the visible item index when the item is chosen in item.layer.layers.items.

I can output the items in a forEach inside the listItemCreatedFunction, but I need to use a watch.

layerListExpand = new Expand({ content: (layerList = new LayerList({ view: view, listItemCreatedFunction: (event) => { let item = event.item; let key = item.title.toUpperCase().replace(/ /g, ''); if (item.layer.type === 'group' || item.layer.type === 'tile') { if (key === 'AERIALS') { item.layer.layers.items?.forEach((item) => { console.log(item.title, item.visible); });

reactiveUtils.when doesn't get hit for item.layer.layers.item

reactiveUtils.when( () => item.layer.layers.items, // I was selected and visible, (visible) => { // do something here if (visible) console.log('visible'); } );

Re: Layerlist selected item becomes visible watch

Sage_Wall — Tue, 29 Oct 2024 21:24:51 GMT

Hi @GregoryBologna ,

reactiveUtils when will only check for truthy values. You would want to use a watch. items isn't part of the public API. You might run into issues. This will also create a watch and a handle for each list item maybe unnecessarily? Not sure on the use case here exactly.

What I would suggest is set up a single watch on map.allLayers something like this. You could expand the filter logic to include only certain layers or layer types if necessary.

// Watching for changes to the visible layers in the Map reactiveUtils.watch( () => view.map.allLayers.filter((layer) => layer.visible), (newVisibleLayers, oldVisibleLayers) => { const added = newVisibleLayers.filter( (layer) => !oldVisibleLayers.includes(layer) ); const removed = oldVisibleLayers.filter( (layer) => !newVisibleLayers.includes(layer) ); added.forEach((layer) => console.log(layer.title, "is visible")); removed.forEach((layer) => console.log(layer.title, "is not visible")); } );

Re: Layerlist selected item becomes visible watch

GregoryBologna — Wed, 30 Oct 2024 20:32:26 GMT

I didn't even think about using at allLayers. Thank you.

Here's how it turned out. Works just right.

// Watching for changes to the visible year layers in the Map reactiveUtils.watch( () => view.map.allLayers.filter((layer) => layer.visible), (newVisibleLayers, oldVisibleLayers) => { const added = newVisibleLayers.filter((layer) => !oldVisibleLayers.includes(layer)); const addedIndices = added.map((layer) => map.allLayers.findIndex((l) => l === layer)); // Destructure with a default value const [yearChosenIndex = null] = addedIndices; chosenPriorYearMapLayer = []; if (yearChosenIndex >= 0) chosenPriorYearMapLayer.push(yearChosenIndex); } );