rainviewer-api-example/rainviewer-google-maps-example.html at master · dewit/rainviewer-api-example · GitHub

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<!DOCTYPE html>
<html>
<head>
    <title>RainViewer API Example for Google Maps</title>

    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <style type="text/css">
        li {
            list-style: none;
            display: inline-block;
        }
    </style>
</head>
<body>

<ul style="text-align:center; position: absolute;top: 0; left: 0; right: 0; height: 50px;">
    <li><input type="button" onclick="stop(); showFrame(animationPosition - 1); return;" value="&lt;" /></li>
    <li><input type="button" onclick="playStop();" value="Play / Stop" /></li>
    <li><input type="button" onclick="stop(); showFrame(animationPosition + 1); return;" value="&gt;" /></li>
</ul>

<div id="timestamp" style="text-align:center; position: absolute;top: 50px; left: 0; right: 0; height: 80px;">FRAME TIME</div>

<div id="mapid" style="position: absolute; top: 80px; left: 0; bottom: 0; right: 0;"></div>

<script>
    var map;
    function initMap() {
        map = new google.maps.Map(document.getElementById('mapid'), {
          center: {lat: 40.633333, lng: -73.716667},
          zoom: 7
        });

        /**
         * Load actual radar animation frames timestamps from RainViewer API
         */
        var apiRequest = new XMLHttpRequest();
        apiRequest.open("GET", "https://api.rainviewer.com/public/maps.json", true);
        apiRequest.onload = function(e) {

            // save available timestamps and show the latest frame: "-1" means "timestamp.lenght - 1"
            timestamps = JSON.parse(apiRequest.response);
            showFrame(-1);
        };
        apiRequest.send();
    }

    /**
     * RainViewer radar animation part
     * @type {number[]}
     */
    var timestamps = [];
    var radarLayers = [];

    var animationPosition = 0;
    var animationTimer = false;

    /**
     * Animation functions
     * @param ts
     */
    function addLayer(ts) {
        if (!radarLayers[ts]) {
            radarLayers[ts] = new google.maps.ImageMapType({
              getTileUrl: function(coord, zoom) {
                return ['https://tilecache.rainviewer.com/v2/radar/' + ts + '/256/',
                    zoom, '/', coord.x, '/', coord.y, '/2/1_1.png'].join('');
              },
              tileSize: new google.maps.Size(256, 256),
              opacity: 0.001
            });
            map.overlayMapTypes.push(radarLayers[ts]);
        }
    }

    /**
     * Display particular frame of animation for the @position
     * If preloadOnly parameter is set to true, the frame layer only adds for the tiles preloading purpose
     * @param position
     * @param preloadOnly
     */
    function changeRadarPosition(position, preloadOnly) {
        while (position >= timestamps.length) {
            position -= timestamps.length;
        }
        while (position < 0) {
            position += timestamps.length;
        }

        var currentTimestamp = timestamps[animationPosition];
        var nextTimestamp = timestamps[position];

        addLayer(nextTimestamp);

        if (preloadOnly) {
            return;
        }

        animationPosition = position;

        if (radarLayers[currentTimestamp]) {
            radarLayers[currentTimestamp].setOpacity(0);
        }
        radarLayers[nextTimestamp].setOpacity(100);

        document.getElementById("timestamp").innerHTML = (new Date(nextTimestamp * 1000)).toString();
    }

    /**
     * Check avialability and show particular frame position from the timestamps list
     */
    function showFrame(nextPosition) {
        var preloadingDirection = nextPosition - animationPosition > 0 ? 1 : -1;

        changeRadarPosition(nextPosition);

        // preload next next frame (typically, +1 frame)
        // if don't do that, the animation will be blinking at the first loop
        changeRadarPosition(nextPosition + preloadingDirection, true);
    }

    /**
     * Stop the animation
     * Check if the animation timeout is set and clear it.
     */
    function stop() {
        if (animationTimer) {
            clearTimeout(animationTimer);
            animationTimer = false;
            return true;
        }
        return false;
    }

    function play() {
        showFrame(animationPosition + 1);

        // Main animation driver. Run this function every 500 ms
        animationTimer = setTimeout(play, 500);
    }

    function playStop() {
        if (!stop()) {
            play();
        }
    }
</script>

<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY_HERE&callback=initMap" async defer></script>

</body>
</html>