How to know radius while drawing a circle on Google Maps

Question

What I have :

As per Google suggestion we have used MVC object and the events DistanceWidget & RadiusWidget to display the radius while re-sizing the circle which is working fine for existing circle (circle drawn by DistanceWidget).

Fiddle Demo

What I need :

I need to show the radius of the circle while drawing a new circle. The event DistanceWidget & RadiusWidget are used only for existing circle (circle drawn by DistanceWidget) not for new circle (user drawn circle by using DrawingManager tool).

Is it possible to show DistanceWidget for creating new circle?

Fiddle

Answer 1

a nice challenge indeed. As @DaveAlperovich has commented, you can't use the DrawingManager to retrieve this piece of information; While drawing, you don't have any access to the circle; You have to wait for the DrawingManager to trigger the circlecomplete event to get a reference to this circle.

Nevertheless, if you can't have a real manager, just fake it. See the snippet and the description right below.

var FakeDrawer = function(controlDiv, map) {
  var self = this;

  /* Initialization, some styling ... */
  self._map = map;
  self.initControls(controlDiv);

  /* Setup the click event listener: drawingmode for the circle control */
  google.maps.event.addDomListener(self._controls.circle, 'click', function() {
    /* Ensure consistency */
    self.reset();

    /* Bind the drawing mode */
    self._map.setOptions({
      draggableCursor: "crosshair"
    });
    self._drawListener = self._map.addListener('mousedown', self.drawingMode(self));
  });

  /* Just reset things for the stop controls */
  google.maps.event.addDomListener(self._controls.stop, 'click', function() {
    self.reset();
  });
};

FakeDrawer.prototype.drawingMode = function(self) {
  return function(center) {
    /* Let's freeze the map during drawing */
    self._map.setOptions({
      draggable: false
    });

    /* Create a new circle which will be manually scaled */
    var circle = new google.maps.Circle({
      fillColor: '#000',
      fillOpacity: 0.3,
      strokeWeight: 2,
      clickable: false,
      editable: false,
      map: self._map,
      radius: 1,
      center: center.latLng,
      zIndex: 1
    });

    /* Update the radius on each mouse move */
    var onMouseMove = self._map.addListener('mousemove', function(border) {
      var radius = 1000 * self.distanceBetweenPoints(center.latLng, border.latLng);
      circle.setRadius(radius);

      /* Here is the feature, know the radius while drawing */
      google.maps.event.trigger(self, 'drawing_radius_changed', circle);
    });

    /* The user has finished its drawing */
    google.maps.event.addListenerOnce(self._map, 'mouseup', function() {
      /* Remove all listeners as they are no more required */
      google.maps.event.removeListener(onMouseMove);

      circle.setEditable(true);

      /* Restore some options to keep a consistent behavior */
      self.reset();

      /* Notify listener with the final circle */
      google.maps.event.trigger(self, 'circlecomplete', circle);
    });
  };
};

FakeDrawer.prototype.reset = function() {
  var self = this;

  self._map.setOptions({
    draggableCursor: "",
    draggable: "true"
  });

  /* Remove any applied listener */
  if (self._drawListener) {
    google.maps.event.removeListener(self._drawListener);
  }
};

/* Create views and associated css */
FakeDrawer.prototype.initControls = function(controlDiv) {
  var self = this;

  function createControlUI(title, image) {
    var controlUI = document.createElement('div');
    controlUI.style.backgroundColor = '#fff';
    controlUI.style.border = '1px solid rgba(0, 0, 0, .15)';
    controlUI.style.boxShadow = '1 4px -1px rgba(0, 0, 0, .3)';
    controlUI.style.marginTop = '10px';
    controlUI.style.textAlign = 'center';
    controlUI.style.width = '25px';
    controlUI.style.height = '25px';
    controlUI.style.display = 'inline-block';
    controlUI.title = title;
    if (image == "circle") {
      controlUI.style.borderLeft = "none";
    }

    var controlImgWrapper = document.createElement('div');
    controlImgWrapper.style.width = '16px';
    controlImgWrapper.style.height = '16px';
    controlImgWrapper.style.overflow = 'hidden';
    controlImgWrapper.style.display = 'inline-block';
    controlImgWrapper.style.marginTop = '4px';
    controlUI.appendChild(controlImgWrapper);

    var imageOffset = {
      "circle": 0,
      "openhand": -9 * 16
    }[image];

    var controlImg = document.createElement('img');
    controlImg.src = 'https://maps.gstatic.com/mapfiles/drawing.png';
    controlImg.style.marginTop = imageOffset + "px";
    controlImgWrapper.appendChild(controlImg);

    var focusBackground = function() {
      controlUI.style.backgroundColor = '#eee';
    };

    var unfocusBackground = function() {
      controlUI.style.backgroundColor = "#fff";
    };

    controlImg.addEventListener('mouseenter', focusBackground);
    controlImg.addEventListener('mouseout', unfocusBackground);
    controlUI.addEventListener('mouseenter', focusBackground);
    controlUI.addEventListener('mouseout', unfocusBackground);

    return controlUI;
  }

  self._controls = {
    circle: createControlUI("Draw a circle", "circle"),
    stop: createControlUI("Stop drawing", "openhand"),
  };

  controlDiv.appendChild(self._controls.stop);
  controlDiv.appendChild(self._controls.circle);
};

FakeDrawer.prototype.distanceBetweenPoints = function(p1, p2) {
  if (!p1 || !p2) {
    return 0;
  }
  var R = 6371;
  var dLat = (p2.lat() - p1.lat()) * Math.PI / 180;
  var dLon = (p2.lng() - p1.lng()) * Math.PI / 180;
  var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(p1.lat() * Math.PI / 180) * Math.cos(p2.lat() * Math.PI / 180) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  var d = R * c;
  return d;
};





function InitializeMap() {
  var latlng = new google.maps.LatLng(29.760193, -95.36939);
  var myOptions = {
    zoom: 12,
    center: latlng,
    zoomControl: true,
    mapTypeId: google.maps.MapTypeId.ROADMAP,
    disableDefaultUI: true
  };
  var map = new google.maps.Map(document.getElementById("map"), myOptions);

  /* Add a custom control */
  var fakeDrawerDiv = document.createElement('div');
  var fakeDrawer = new FakeDrawer(fakeDrawerDiv, map);

  fakeDrawerDiv.index = 1;
  map.controls[google.maps.ControlPosition.TOP_CENTER].push(fakeDrawerDiv);


  var updateInfo = function(circle) {
    document.getElementById("info").innerHTML = "Radius: " + circle.getRadius();
  };

  google.maps.event.addListener(fakeDrawer, 'drawing_radius_changed', updateInfo);
  google.maps.event.addListener(fakeDrawer, 'circlecomplete', function(circle) {
    google.maps.event.addListener(circle, 'radius_changed', function() {
      updateInfo(circle);
    });
  });
}


google.maps.event.addDomListener(window, 'load', InitializeMap);

html,
body {
  height: 100%;
  margin: 0px;
  padding: 0px
}
#map {
  height: 80%;
  width: 100%;
}

<script src="https://maps.googleapis.com/maps/api/js?v=3&libraries=drawing&ext=.js"></script>
<div id="map"></div>
<div id="info"></div>

Step 1: Create a custom control

Somewhere in the file or as an external library:

var FakeDrawer = function (controlDiv, map) {
    var self = this;

    /* Initialization, some styling ... */
    self._map = map;
    self.initControls(controlDiv);
};

FakeDrawer.prototype.initControls(controlDiv) {
    var self = this;

    function createControlUI (title, image) {
        var controlUI = document.createElement('div');
        /* ... See the snippet for details .. just some styling */
        return controlUI;
    }

    self._controls = {
        circle: createControlUI("Draw a circle", "circle"),
        stop: createControlUI("Stop drawing", "openhand"),
     };

     controlDiv.appendChild(self._controls.stop);
     controlDiv.appendChild(self._controls.circle);
};

Step 2: Add some sugars

This are functions that we may use; Highly inspired from your JsFiddle :)

A reset method to recover a consistent state when needed:

FakeDrawer.prototype.reset = function () {
    var self = this;
    self._map.setOptions({
        draggableCursor: "",
        draggable: "true"
    });

    /* Remove any applied listener */
    if (self._drawListener) { google.maps.event.removeListener(self._drawListener) ; }
};

And, a distance computer:

FakeDrawer.prototype.distanceBetweenPoints = function (p1, p2) {
    if (!p1 || !p2) {
        return 0;
    }
    var R = 6371;
    var dLat = (p2.lat() - p1.lat()) * Math.PI / 180;
    var dLon = (p2.lng() - p1.lng()) * Math.PI / 180;
    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(p1.lat() * Math.PI / 180) * Math.cos(p2.lat() * Math.PI / 180) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    var d = R * c;
    return d;
};

Step 3: Create your own drawing mode

Now that we have some controls, we have to define their behavior. The stop control is straightforward; Let's have a look to the circle control.

FakeDrawer.prototype.drawingMode = function (self) {
    return function (center) {
        /* Let's freeze the map during drawing */
        self._map.setOptions({draggable: false});

        /* Create a new circle which will be manually scaled */
        var circle = new google.maps.Circle({
            fillColor: '#000',
            fillOpacity: 0.3,
            strokeWeight: 2,
            clickable: false,
            editable: false,
            map: self._map,
            radius: 1,
            center: center.latLng,
            zIndex: 1
        });

        /* Update the radius on each mouse move */
        var onMouseMove = self._map.addListener('mousemove', function (border) {
            var radius = 1000 * self.distanceBetweenPoints(center.latLng, border.latLng);
            circle.setRadius(radius);

            /* Here is the feature, know the radius while drawing */
            google.maps.event.trigger(self, 'drawing_radius_changed', circle);
        });

        /* The user has finished its drawing */
        google.maps.event.addListenerOnce(self._map, 'mouseup', function () {
            /* Remove all listeners as they are no more required */
            google.maps.event.removeListener(onMouseMove);

            circle.setEditable(true);

            /* Restore some options to keep a consistent behavior */
            self.reset();

            /* Notify listener with the final circle */
            google.maps.event.trigger(self, 'circlecomplete', circle);
        });
    };
};

Step 4: Bind controls

Now that everything is okay, let's add some listeners to the initial version of the constructor so that each control has a corresponding action when clicked.

var FakeDrawer = function (controlDiv, map) {
    var self = this;

    /* Initialization, some styling ... */
    self._map = map;
    self.initControls(controlDiv);

    /* Setup the click event listeners: drawingmode */
    google.maps.event.addDomListener(self._controls.circle, 'click', function() {
        /* Ensure consistency */
        self.reset();

        /* Only drawingmode */
        self._map.setOptions({draggableCursor: "crosshair"});
        self._drawListener = self._map.addListener('mousedown', self.drawingMode(self));
    });

    google.maps.event.addDomListener(self._controls.stop, 'click', function () {
        self.reset();
    });
};

Step 5: Use it!

Assuming that your map has been initialized correctly.

Inside your map init function:

var fakeDrawerDiv = document.createElement('div');
var fakeDrawer = new FakeDrawer(fakeDrawerDiv, map);

fakeDrawerDiv.index = 1;
map.controls[google.maps.ControlPosition.TOP_CENTER].push(fakeDrawerDiv);

var updateInfo = function (circle) {
    document.getElementById("info").innerHTML = "Radius: " + circle.getRadius();
};

google.maps.event.addListener(fakeDrawer, 'drawing_radius_changed', updateInfo);
google.maps.event.addListener(fakeDrawer, 'circlecomplete', function (circle) {
    google.maps.event.addListener(circle, 'radius_changed', function () {
        updateInfo(circle);
    });
});

Enjoy, hope it will help.