[GIS] Event listeners after each plotting of a point of a Polygon Vector in OpenLayers

eventsjavascriptopenlayers-2

I am quite new to OpenLayers. I have a polygonLayer for users to draw polygon vectors. The plotting feature is working fine. 

polygonLayer = new OpenLayers.Layer.Vector("Polygon Layer");
map.addLayers([ polygonLayer ]);
var polygonControl = new OpenLayers.Control.DrawFeature(polygonLayer, OpenLayers.Handler.Polygon);
map.addControl(polygonControl);
polygonControl.activate();
var editControl = new OpenLayers.Control.ModifyFeature(polygonLayer);
map.addControl(editControl);
editControl.activate(RESIZE);

What I want to do is to have event listeners after each plotting of a point. Supposedly, I want to show popups to assist the user in between each point of plotting. How could I achieve it?

Best Answer

Here's a simple way to get the coordinates of points as you draw them:

// Pass these options to the DrawFeature constructor:
var drawOptions = {
    callbacks : {
        "done": doneHandler,
        "point": pointHandler
    },
};

drawControls = {
    point: new OpenLayers.Control.DrawFeature(pointLayer, OpenLayers.Handler.Point),
    line: new OpenLayers.Control.DrawFeature(lineLayer, OpenLayers.Handler.Path, drawOptions),
    polygon: new OpenLayers.Control.DrawFeature(polygonLayer, OpenLayers.Handler.Polygon, drawOptions)
};

// called when the feature is complete (double-clicked)
function doneHandler(lineGeom) {
    console.log("DONE:" + lineGeom.getVertices());
}


// called on each point drawn    
function pointHandler(aPoint) {
    console.log(aPoint.toString());
}
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