Symbology visualisation based on Hit Test Arcgis Javascript API

Question

Hi. I have two feature service layers representing same data . One layer is of a simple point symbology(layer1) and another a picture marker symbology(layer2). Two layers are overlayed one over the other

I would like to view the picture marker symbolgy (Layer2) on clicking the point symbology (Layer1).

I read the "Hit Test" content in the developer resources guide. I was unable to find any examples of how to accomplish this. Can anyone offer assistance?

MANESK · Answer

Thanks Christer for your response.  I would like to show the feature from layer2 that matches with the clicked feature of layer 1. I will try with the logic mentioned and work with it.

Christer · Answer

Are you looking to show the entire layer2 when clicking any point on layer1 ? or just the feature from layer2 that matches with the clicked feature of layer1?

When loading layer2, you could pass inn a definitionexpression (filter) which will always return 0 entries in the beginning. And by clicking on a feature in layer1, you could update that filter based on fields that would match 1-to-1 with the result of the hitTest, making layer2 only show what is returned by the updated filter.

Sample:

layer2 = new FeatureLayer({...., definitionExpression: 'Id = -1'})

const eventRef = view.on('immediate-click', (event) => {
      const options = {
        include: layer1,
      };

view.hitTest(event, options).then((response) => {
        if (!response.results.length) return; // no hit
        const result = response.results[0] as __esri.GraphicHit;
        const primaryKey = result.graphic.attributes['Id'];
        layer2.definitionExpression = $`Id={primaryKey}`
      });
    });

Something in the lines of the above i think would work. A bit of pseudo code, so you need to ofcourse adapt it.