Tile Load Events

This example uses OpenLayers v4.0.1. The latest is v.

#### Tile Load Events

Example using tile load events.

Image tile sources fire events related to tile loading. You can listen for `tileloadstart`, `tileloadend`, and `tileloaderror` type events to monitor tile loading progress. This example registers listeners for these events and renders a tile loading progress bar at the bottom of the map.

Related API documentation:

- ol.Map
,
- ol.View
,
- ol.layer.Tile
,
- ol.source.TileJSON

Copy Edit
Tile Load Events Example using tile load events. /** * Renders a progress bar. * @param {Element} el The target element. * @constructor */ function Progress(el) { this.el = el; this.loading = 0; this.loaded = 0; } /** * Increment the count of loading tiles. */ Progress.prototype.addLoading = function() { if (this.loading === 0) { this.show(); } ++this.loading; this.update(); }; /** * Increment the count of loaded tiles. */ Progress.prototype.addLoaded = function() { var this_ = this; setTimeout(function() { ++this_.loaded; this_.update(); }, 100); }; /** * Update the progress bar. */ Progress.prototype.update = function() { var width = (this.loaded / this.loading * 100).toFixed(1) + '%'; this.el.style.width = width; if (this.loading === this.loaded) { this.loading = 0; this.loaded = 0; var this_ = this; setTimeout(function() { this_.hide(); }, 500); } }; /** * Show the progress bar. */ Progress.prototype.show = function() { this.el.style.visibility = 'visible'; }; /** * Hide the progress bar. */ Progress.prototype.hide = function() { if (this.loading === this.loaded) { this.el.style.visibility = 'hidden'; this.el.style.width = 0; } }; var progress = new Progress(document.getElementById('progress')); var source = new ol.source.TileJSON({ url: 'https://api.tiles.mapbox.com/v3/mapbox.world-bright.json?secure', crossOrigin: 'anonymous' }); source.on('tileloadstart', function() { progress.addLoading(); }); source.on('tileloadend', function() { progress.addLoaded(); }); source.on('tileloaderror', function() { progress.addLoaded(); }); var map = new ol.Map({ logo: false, layers: [ new ol.layer.Tile({source: source}) ], target: 'map', view: new ol.View({ center: [0, 0], zoom: 2 }) }); .map { background: #E0ECED; } .wrapper { position: relative; } #progress { position: absolute; bottom: 0; left: 0; height: 2px; background: rgba(0, 60, 136, 0.4); width: 0; transition: width 250ms; } <div class="wrapper"> <div id="map" class="map"></div> <div id="progress"></div> </div>

    <!DOCTYPE html>
    <html>
      <head>
        <title>Tile Load Events</title>
        <link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css">
        <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
        <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
        <script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script>
        <style>
          .map {
            background: #E0ECED;
          }
          .wrapper {
            position: relative;
          }
          #progress {
            position: absolute;
            bottom: 0;
            left: 0;
            height: 2px;
            background: rgba(0, 60, 136, 0.4);
            width: 0;
            transition: width 250ms;
          }    </style>
      </head>
      <body>
        <div class="wrapper">
          <div id="map" class="map"></div>
          <div id="progress"></div>
        </div>
        <script>
          /**
           * Renders a progress bar.
           * @param {Element} el The target element.
           * @constructor
           */
          function Progress(el) {
            this.el = el;
            this.loading = 0;
            this.loaded = 0;
          }

          /**
           * Increment the count of loading tiles.
           */
          Progress.prototype.addLoading = function() {
            if (this.loading === 0) {
              this.show();
            }
            ++this.loading;
            this.update();
          };

          /**
           * Increment the count of loaded tiles.
           */
          Progress.prototype.addLoaded = function() {
            var this_ = this;
            setTimeout(function() {
              ++this_.loaded;
              this_.update();
            }, 100);
          };

          /**
           * Update the progress bar.
           */
          Progress.prototype.update = function() {
            var width = (this.loaded / this.loading * 100).toFixed(1) + '%';
            this.el.style.width = width;
            if (this.loading === this.loaded) {
              this.loading = 0;
              this.loaded = 0;
              var this_ = this;
              setTimeout(function() {
                this_.hide();
              }, 500);
            }
          };

          /**
           * Show the progress bar.
           */
          Progress.prototype.show = function() {
            this.el.style.visibility = 'visible';
          };

          /**
           * Hide the progress bar.
           */
          Progress.prototype.hide = function() {
            if (this.loading === this.loaded) {
              this.el.style.visibility = 'hidden';
              this.el.style.width = 0;
            }
          };

          var progress = new Progress(document.getElementById('progress'));

          var source = new ol.source.TileJSON({
            url: 'https://api.tiles.mapbox.com/v3/mapbox.world-bright.json?secure',
            crossOrigin: 'anonymous'
          });

          source.on('tileloadstart', function() {
            progress.addLoading();
          });

          source.on('tileloadend', function() {
            progress.addLoaded();
          });
          source.on('tileloaderror', function() {
            progress.addLoaded();
          });

          var map = new ol.Map({
            logo: false,
            layers: [
              new ol.layer.Tile({source: source})
            ],
            target: 'map',
            view: new ol.View({
              center: [0, 0],
              zoom: 2
            })
          });
        </script>
      </body>
    </html>