ArcGIS Interaction

Use this skill when implementing user interactions like hit testing, feature highlighting, sketching, coordinate conversion, and event handling.

Import Patterns

Direct ESM Imports

import Draw from "@arcgis/core/views/draw/Draw.js";
import * as reactiveUtils from "@arcgis/core/core/reactiveUtils.js";

Dynamic Imports (CDN)

const Draw = await $arcgis.import("@arcgis/core/views/draw/Draw.js");
const reactiveUtils = await $arcgis.import(
  "@arcgis/core/core/reactiveUtils.js",
);

Note: The examples in this skill use Direct ESM imports. For CDN usage, replace import X from "path" with const X = await $arcgis.import("path").

Hit Testing

Basic Hit Test

view.on("click", async (event) => {
  const response = await view.hitTest(event);

  if (response.results.length > 0) {
    const graphic = response.results[0].graphic;
    console.log("Clicked feature:", graphic.attributes);
  }
});

Hit Test with Layer Filter

view.on("click", async (event) => {
  const response = await view.hitTest(event, {
    include: [featureLayer], // Only test this layer
  });

  // Or exclude layers
  const response2 = await view.hitTest(event, {
    exclude: [graphicsLayer],
  });
});

Pointer Move Hit Test

view.on("pointer-move", async (event) => {
  const response = await view.hitTest(event, {
    include: featureLayer,
  });

  if (response.results.length > 0) {
    document.body.style.cursor = "pointer";
  } else {
    document.body.style.cursor = "default";
  }
});

Hit Test Result Types

The hitTest returns ViewHitTestResult containing an array of result objects. Each result has a type:

view.on("click", async (event) => {
  const response = await view.hitTest(event);

  response.results.forEach((result) => {
    if (result.type === "graphic") {
      console.log("Layer:", result.graphic.layer.title);
      console.log("Attributes:", result.graphic.attributes);
    }
  });
});

Highlighting

Highlight Features

const layerView = await view.whenLayerView(featureLayer);

// Highlight a single feature
const highlight = layerView.highlight(graphic);

// Highlight multiple features
const highlight = layerView.highlight([graphic1, graphic2]);

// Highlight by object IDs
const highlight = layerView.highlight([1, 2, 3]);

// Remove highlight
highlight.remove();

Highlight on Click

let highlightHandle;

view.on("click", async (event) => {
  // Remove previous highlight
  if (highlightHandle) {
    highlightHandle.remove();
  }

  const response = await view.hitTest(event, { include: featureLayer });

  if (response.results.length > 0) {
    const graphic = response.results[0].graphic;
    const layerView = await view.whenLayerView(featureLayer);
    highlightHandle = layerView.highlight(graphic);
  }
});

Highlight Options

// Set highlight options on the view
view.highlightOptions = {
  color: [255, 255, 0, 1],
  haloOpacity: 0.9,
  fillOpacity: 0.2,
};

Sketching

Sketch Component (Simplest)

<arcgis-map basemap="topo-vector" center="139.5716,35.696" zoom="18">
  <arcgis-sketch slot="top-right" creation-mode="update"></arcgis-sketch>
</arcgis-map>

The arcgis-sketch component provides drawing tools for point, polyline, polygon, rectangle, and circle geometries with snapping, undo/redo, and selection support.

Key Attributes:

Key Events:

Key Methods:

Sketch Component with Events

<arcgis-map basemap="topo-vector">
  <arcgis-sketch slot="top-right" creation-mode="update"></arcgis-sketch>
</arcgis-map>

<script type="module">
  const sketch = document.querySelector("arcgis-sketch");

  sketch.addEventListener("arcgisCreate", (event) => {
    const { state, graphic } = event.detail;
    if (state === "complete") {
      console.log("Created:", graphic.geometry.type);
    }
  });

  sketch.addEventListener("arcgisUpdate", (event) => {
    const { state, graphics } = event.detail;
    if (state === "complete") {
      console.log("Updated:", graphics.length, "graphics");
    }
  });

  sketch.addEventListener("arcgisDelete", (event) => {
    console.log("Deleted:", event.detail.graphics.length, "graphics");
  });
</script>

Sketch Widget (Core API)

import Sketch from "@arcgis/core/widgets/Sketch.js";
import GraphicsLayer from "@arcgis/core/layers/GraphicsLayer.js";

const graphicsLayer = new GraphicsLayer();
map.add(graphicsLayer);

const sketch = new Sketch({
  view: view,
  layer: graphicsLayer,
  creationMode: "update", // or "single", "continuous"
});

view.ui.add(sketch, "top-right");

// Listen for events
sketch.on("create", (event) => {
  if (event.state === "complete") {
    console.log("Created:", event.graphic);
  }
});

sketch.on("update", (event) => {
  if (event.state === "complete") {
    console.log("Updated:", event.graphics);
  }
});

sketch.on("delete", (event) => {
  console.log("Deleted:", event.graphics);
});

Draw Tool (Low-level)

import Draw from "@arcgis/core/views/draw/Draw.js";

const draw = new Draw({ view: view });

// Create a polygon
const action = draw.create("polygon");

action.on("vertex-add", (event) => {
  console.log("Vertex added:", event.vertices);
});

action.on("draw-complete", (event) => {
  const polygon = {
    type: "polygon",
    rings: event.vertices,
    spatialReference: view.spatialReference,
  };
  // Create graphic with polygon
});

Event Handling

View Events

// Click (waits for potential double-click delay)
view.on("click", (event) => {
  console.log("Map point:", event.mapPoint);
  console.log("Screen point:", event.x, event.y);
});

// Immediate-click (fires without delay, recommended for hit testing)
view.on("immediate-click", (event) => {
  console.log("Immediate click at:", event.mapPoint);
});

// Double-click
view.on("double-click", (event) => {
  event.stopPropagation(); // Prevent default zoom
});

// Immediate-double-click (cannot be prevented by immediate-click stopPropagation)
view.on("immediate-double-click", (event) => {
  console.log("Double clicked");
});

// Pointer move
view.on("pointer-move", (event) => {
  const point = view.toMap(event);
  console.log("Coordinates:", point.longitude, point.latitude);
});

// Drag
view.on("drag", (event) => {
  if (event.action === "start") {
  }
  if (event.action === "update") {
  }
  if (event.action === "end") {
  }
});

// Key events
view.on("key-down", (event) => {
  if (event.key === "Escape") {
    // Cancel operation
  }
});

Tip: Use immediate-click instead of click when responding to user clicks without delay (e.g., for hit testing). The click event waits to check for a double-click, which adds latency.

Property Watching with reactiveUtils

import * as reactiveUtils from "@arcgis/core/core/reactiveUtils.js";

// Watch for view stationary state
reactiveUtils.when(
  () => view.stationary === true,
  () => {
    console.log("Navigation complete, extent:", view.extent);
  },
);

// Watch zoom changes
reactiveUtils.watch(
  () => view.zoom,
  (zoom) => {
    console.log("Zoom changed to:", zoom);
  },
);

// Watch multiple properties
reactiveUtils.watch(
  () => [view.center, view.zoom],
  ([center, zoom]) => {
    console.log("View changed:", center, zoom);
  },
);

// One-time wait
await reactiveUtils.whenOnce(() => view.ready);
console.log("View is ready");

Layer Events

const layerView = await view.whenLayerView(featureLayer);

reactiveUtils.watch(
  () => layerView.updating,
  (updating) => {
    if (!updating) {
      console.log("Layer update complete");
    }
  },
);

Coordinate Conversion

// Screen to map coordinates
const mapPoint = view.toMap({ x: screenX, y: screenY });

// Map to screen coordinates
const screenPoint = view.toScreen(mapPoint);

Programmatic Popup Control

For detailed PopupTemplate configuration, see arcgis-popup-templates.

// Open popup programmatically
view.openPopup({
  title: "Custom Popup",
  content: "Hello World",
  location: view.center,
});

// Close popup
view.closePopup();

Complete Example: Hit Test with Highlight

Map Components

<!DOCTYPE html>
<html>
  <head>
    <script src="https://js.arcgis.com/5.0/"></script>
    <script
      type="module"
      src="https://js.arcgis.com/5.0/map-components/"
    ></script>
    <style>
      html,
      body {
        height: 100%;
        margin: 0;
      }
    </style>
  </head>
  <body>
    <arcgis-map
      basemap="streets-navigation-vector"
      center="-118.805,34.027"
      zoom="13"
    >
      <arcgis-zoom slot="top-left"></arcgis-zoom>
    </arcgis-map>

    <script type="module">
      const [FeatureLayer] = await $arcgis.import([
        "@arcgis/core/layers/FeatureLayer.js",
      ]);

      const mapElement = document.querySelector("arcgis-map");
      const view = await mapElement.view;
      await view.when();

      const featureLayer = new FeatureLayer({
        url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0",
      });
      mapElement.map.add(featureLayer);

      let highlightHandle;

      view.on("pointer-move", async (event) => {
        const response = await view.hitTest(event, { include: featureLayer });

        if (highlightHandle) {
          highlightHandle.remove();
          highlightHandle = null;
        }

        if (response.results.length > 0) {
          const graphic = response.results[0].graphic;
          const layerView = await view.whenLayerView(featureLayer);
          highlightHandle = layerView.highlight(graphic);
          document.body.style.cursor = "pointer";
        } else {
          document.body.style.cursor = "default";
        }
      });
    </script>
  </body>
</html>

Reference Samples

• view-hittest - Hit testing to identify features at screen coordinates
• map-component-hittest - Access features with hitTest using Map Components
• sketch - Sketch component for drawing geometries
• sketch-geometries - Sketching geometries with the Sketch widget
• sketch-update-validation - Validating sketch updates
• sketch-snapping-magnifier - Snapping and magnifier with Sketch

Common Pitfalls

1. Highlight handle leak: Creating new highlights without removing previous ones causes memory leaks.

   // Anti-pattern: creating highlights without cleaning up previous ones
   view.on("pointer-move", async (event) => {
     const response = await view.hitTest(event);
     if (response.results.length > 0) {
       const feature = response.results[0].graphic;
       // New highlight created every pointer-move - old ones never removed
       layerView.highlight(feature);
     }
   });

   // Correct: store handle and remove before creating a new highlight
   let highlightHandle = null;
   
   view.on("pointer-move", async (event) => {
     const response = await view.hitTest(event);
     if (highlightHandle) {
       highlightHandle.remove();
       highlightHandle = null;
     }
     if (response.results.length > 0) {
       const feature = response.results[0].graphic;
       highlightHandle = layerView.highlight(feature);
     }
   });

   Impact: Each pointer-move adds another highlight without removing the previous one. Highlights accumulate visually and in memory, causing performance degradation.

2. Events fire multiple times: Adding event listeners repeatedly without cleanup causes handler accumulation.

   // Anti-pattern: adding listeners in a function that gets called multiple times
   function setupInteraction() {
     view.on("click", async (event) => {
       const result = await view.hitTest(event);
       console.log("Clicked:", result);
     });
   }
   setupInteraction(); // First handler
   setupInteraction(); // Second handler - now click fires twice

   // Correct: store handle and remove before re-adding, or add once
   let clickHandle = null;
   
   function setupInteraction() {
     if (clickHandle) {
       clickHandle.remove();
     }
     clickHandle = view.on("click", async (event) => {
       const result = await view.hitTest(event);
       console.log("Clicked:", result);
     });
   }

   Impact: Each call to the setup function adds another listener. Clicks fire multiple duplicate callbacks.

3. Hit test returns nothing: Check if layers are included/excluded correctly, and ensure the view is ready.
4. Using click instead of immediate-click: The click event has a built-in delay to check for double-clicks. Use immediate-click for responsive hit testing.
5. Popup not showing: Ensure layer has popupEnabled: true (default) and a popupTemplate set.

Related Skills

• See arcgis-popup-templates for detailed PopupTemplate configuration.
• See arcgis-editing for feature editing workflows.
• See arcgis-core-maps for view initialization and navigation.