How to populate Longitude/Latitude form fields 'onclick' and add location marker to map?

SteveCheshire · ‎12-28-2020

Hello

I'm trying to build a wildlife recording form for a charity to collect wildlife sightings data and I would like to use ESRI maps to collect Longitude and Latitude location data. Unfortunately I'm very new to all this so learning on the job!

I have an iframe containing the file record_map.php that displays the map (see code below). When I click on the map, I want the the Longitude and Latitude of that location to populate two html form fields in the parent document i.e. <input type="number" id="Longitude" name="Longitude" value=""> and <input type="number" id="Latitude" name="Latitude" value="">.

I also need to pin a graphic or point to the selected location on the map 'onclick' and for this to move to a new location if the user clicks a different place on the map?

Any help would be very much appreciated. Huge thank you to anyone who can help.
Seasons greetings!

Steve

Here's the code for record_map.php

<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1, user-scalable=no">
<style>
html, body, #viewDiv {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
}
</style>

<link rel="stylesheet" href="https://js.arcgis.com/4.11/esri/css/main.css">
<script src="https://js.arcgis.com/4.11/"></script>

<script type="text/javascript">
//LOAD LAYERS
require([
"esri/tasks/Locator",
"esri/Map",
"esri/views/MapView",
"esri/Graphic",
"esri/layers/GraphicsLayer",
"esri/widgets/BasemapToggle",
"esri/widgets/BasemapGallery"
], function(Locator, Map, MapView, Graphic, GraphicsLayer, BasemapToggle, BasemapGallery) {

// SET LOCATOR TASK USING WORLD GEOCODING SERVICE
var locatorTask = new Locator({
url:
"https://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer"
});

//LOAD INITIAL BASE LAYER TYPE
var map = new Map({
basemap: "topo-vector"
});

//LOCATE MAP CENTER AND ZOOM LEVEL
var view = new MapView({
container: "viewDiv",
map: map,
center: [19.874268,39.576056], // longitude, latitude
zoom: 10
});

//TOGGLE BASE LAYER TYPE
var basemapToggle = new BasemapToggle({
view: view,
nextBasemap: "satellite"
});

//POSITION BASE LAYER TOGGLE
view.ui.add(basemapToggle, "bottom-left");

//POSITION BASE LAYER TOGGLE
var graphicsLayer = new GraphicsLayer();
map.add(graphicsLayer);

//FORMAT RECORD POINT STYLE
var simpleMarkerSymbol = {
type: "simple-marker",
color: [220, 53, 69, 1], // orange
outline: {
color: [255, 255, 255, 1], // white
width: 2
}
};

var pointGraphic = new Graphic({
geometry: point,
symbol: simpleMarkerSymbol
});

graphicsLayer.add(pointGraphic);

//LOAD OUTLINE POLYGON
var polygon = {
type: "polygon",
rings: [
[ 19.6549, 39.7353 ], [ 19.6549, 39.7353 ]
]
};

var simpleFillSymbol = {
type: "simple-fill",
color: [0, 190, 90, 0.025], // CBC Green, opacity 2.5%
outline: {
color: [0, 190, 90, 1],
width: 1
}
};

var polygonGraphic = new Graphic({
geometry: polygon,
symbol: simpleFillSymbol
});

graphicsLayer.add(polygonGraphic);

//LOAD AND FORMAT CO-ORDINATE WIDGET TO DISPLAY LONG/LAT, SCALE AND ZOOM LEVEL
var coordsWidget = document.createElement("div");
coordsWidget.id = "coordsWidget";
coordsWidget.className = "esri-widget esri-component";
coordsWidget.style.padding = "7px 15px 5px";

view.ui.add(coordsWidget, "bottom-right");

function showCoordinates(pt) {
var coords =
"Latitude " +
pt.latitude.toFixed(6) +
" | Longitude " +
pt.longitude.toFixed(6) +
" | Scale 1:" +
Math.round(view.scale * 1) / 1 +
" | Zoom " +
view.zoom;
coordsWidget.innerHTML = coords;
}

view.watch("stationary", function (isStationary) {
showCoordinates(view.center);
});

view.on("pointer-move", function (evt) {
showCoordinates(view.toMap({ x: evt.x, y: evt.y }));
});
});
</script>

</head>
<body>
<div id="viewDiv"></div>
</body>
</html>

BlakeTerhune · ‎12-28-2020

The hittest() method of MapView will have a mapPoint property in the HitTestResult that is returned. You can use the latitude and longitude properties of the point.

SteveCheshire · ‎12-28-2020

Thanks Blake. How would I implement that within my code? I've searched everywhere for a working example/code but to no avail.

BlakeTerhune · ‎12-28-2020

There's two examples in the hittest() documentation section as well as a link to a sample app using hittest(). In your case, sounds like you want a click event so start with that example.

// Get the screen point from the view's click event
view.on("click", function (event) {
  // Search for graphics at the clicked location. View events can be used
  // as screen locations as they expose an x,y coordinate that conforms
  // to the ScreenPoint definition.
  view.hitTest(event).then(function (response) {
    if (response.results.length) {
      var graphic = response.results.filter(function (result) {
        // check if the graphic belongs to the layer of interest
        return result.graphic.layer === myLayer;
      })[0].graphic;

      // do something with the result graphic
      console.log(graphic.attributes);
    }
  });
});

Then you can display the mapPoint from HitTestResult as a graphic.