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3 min read 02-10-2024
react-map-gl highlight

Highlighting Features on Your React Map: Mastering React Map GL

Want to draw attention to specific locations or features on your React Map GL map? Highlighting is a powerful technique to enhance user experience and convey important information. This article will guide you through the process of effectively highlighting features on your map using React Map GL.

The Challenge

Let's say you have a map displaying various points of interest. You want to highlight a specific point when the user hovers over it, making it visually stand out from the rest. This is where React Map GL's powerful highlighting capabilities come into play.

Original Code Example (Using a Simple Example)

import React, { useState, useEffect } from 'react';
import ReactMapGL from 'react-map-gl';

function MyMap() {
  const [viewport, setViewport] = useState({
    latitude: 37.7749,
    longitude: -122.4194,
    zoom: 10,
  });

  const [highlightedFeature, setHighlightedFeature] = useState(null);

  const handleHover = (event) => {
    const feature = event.features && event.features[0];
    setHighlightedFeature(feature);
  };

  return (
    <ReactMapGL
      {...viewport}
      onViewportChange={setViewport}
      mapboxApiAccessToken={process.env.REACT_APP_MAPBOX_TOKEN}
      onHover={handleHover}
    >
      {/* ... your map features */}
    </ReactMapGL>
  );
}

export default MyMap;

Understanding the Code

This example demonstrates a simple approach to highlighting features on hover. We use the onHover event of React Map GL, which provides information about the feature being hovered over. In the handleHover function, we capture the first feature (if any) from the event's features array and store it in the highlightedFeature state.

Implementing Effective Highlighting

Now, let's delve into the actual highlighting process. We can achieve this by using React Map GL's Layer component and customizing its paint properties based on the highlightedFeature state.

Here's how you can enhance the previous example:

// ... imports and other code ...

function MyMap() {
  // ... state variables ... 

  return (
    <ReactMapGL
      {...viewport}
      onViewportChange={setViewport}
      mapboxApiAccessToken={process.env.REACT_APP_MAPBOX_TOKEN}
      onHover={handleHover}
    >
      {/* ... your map features */}
      <Layer
        id="highlighted-feature"
        type="circle"
        paint={{
          'circle-radius': [
            'case',
            ['boolean', ['feature-state', 'hover'], false],
            8, // radius for highlighted feature
            4 // radius for other features
          ],
          'circle-color': [
            'case',
            ['boolean', ['feature-state', 'hover'], false],
            'red', // color for highlighted feature
            'blue' // color for other features
          ]
        }}
        source={{
          type: 'geojson',
          data: {
            type: 'FeatureCollection',
            features: [highlightedFeature || {}] // Use highlightedFeature
          }
        }}
      />
    </ReactMapGL>
  );
}

// ... other code ...

Explanation of Enhancements

  1. Layer Component: We introduce a new Layer component, named highlighted-feature, with the type set to circle. This will allow us to control the appearance of our highlighted feature.

  2. paint Properties: The paint object within the Layer controls visual styling. The 'circle-radius' and 'circle-color' properties use conditional statements (using case and feature-state) to dynamically adjust the radius and color based on whether the feature is hovered over or not.

  3. source Property: The source property is crucial. It's defined as a geojson source, and the data property is set to a FeatureCollection containing our highlightedFeature object. This dynamic update allows us to focus on only the highlighted feature.

Important Notes:

  • Optimization: For better performance, consider using interactive layers in your React Map GL setup. This allows for efficient hover interactions, improving the user experience.

  • Customization: Explore the vast array of styling options available in the React Map GL documentation to tailor your highlighting to your specific needs. You can adjust colors, radii, opacity, and more to achieve the desired visual effect.

Resources:

By following these steps and utilizing the power of React Map GL, you can create interactive maps that effectively highlight and draw attention to specific locations or features, enhancing the user experience and conveying important information.

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