jquery.ios-shake.js

/*
jquery.ios-shake: A jQuery plugin that detects a 'shake' event using
Safari's accelerometer support in iOS 4.2+.

Revision History:
0.1.0 - 2011-01-24 - initial release

Copyright 2011 Luke D Hagan, http://lukehagan.com

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/

(function($) {
    jQuery.shake = function(options) {
        // Merge passed options with defaults
        var opts = jQuery.extend({},
        jQuery.shake.defaults, options);

        // insert debug content
        if (opts.debug !== "") {
            var debug = $(opts.debug);
            debug.append('x: <span id="x">0</span><br>');
            debug.append('y: <span id="y">0</span><br>');
            debug.append('z: <span id="z">0</span><br><br>');

            debug.append('shake: <span id="shake">0</span><br>');
            debug.append('shakeaccum: <span id="shakeaccum"></span><br>');
            debug.append('debug: <span id="console"></span><br>');
        }

        // initialize acceleration variables
        var ax = 0;
        var ay = 0;
        var az = 0;
        var axa = 0;
        var aya = 0;
        var aza = 0;

        // initialize misc internal variables
        var shakecount = 0;
        var shakeaccum = 0;
        var curtime = new Date();
        var prevtime = new Date();
        var timeout = false;

        // http://www.mobilexweb.com/samples/ball.html
        // detect whether acceleration is supported
        if (window.DeviceMotionEvent === undefined) {
            if (opts.supported !== "") {
                $(opts.supported).html("Your browser does not support Device Orientation and Motion API. Try it on an iPhone, iPod or iPad with iOS 4.2+.");
            }
        } else {
            window.ondevicemotion = function(event) {
                // get acceleration values
                var acc = event.accelerationIncludingGravity;
                ax = acc.x;
                ay = acc.y;
                az = acc.y;

                // high pass-filter to remove gravity
                // TODO detect and use gyro (no gravity) on supported devices
                // http://iphonedevelopertips.com/user-interface/accelerometer-101.html
                axa = ax - ((ax * opts.hf) + (axa * (1.0 - opts.hf)));
                aya = ay - ((ay * opts.hf) + (aya * (1.0 - opts.hf)));
                aza = az - ((az * opts.hf) + (aza * (1.0 - opts.hf)));

                // detect single shake
                // http://discussions.apple.com/thread.jspa?messageID=8224655
                var beenhere = false;
                var shake = false;
                if (beenhere) {
                    return;
                }
                beenhere = true;
                if (Math.abs(ax - 2 * axa) > opts.violence * 1.5 || Math.abs(ay - 2 * aya) > opts.violence * 2 || Math.abs(az - 2 * aza) > opts.violence * 3 && timeout === false) {
                    shakeaccum += 1;
                }

                // detect shake event (several shakes)
                curtime = new Date();
                var timedelta = curtime.getTime() - prevtime.getTime();
                $('#console').html(timedelta);

                if (timeout) {
                    if (timedelta >= opts.debounce) {
                        timeout = false;
                    } else {
                        timeout = true;
                    }
                    shakeaccum = 0;
                }

                if (shakeaccum >= opts.shakethreshold && timeout === false) {
                    shakecount += 1;
                    $("#shake").html(shakecount);
                    prevtime = curtime;
                    timeout = true;
                    opts.callback.call();
                }
                beenhere = true;
            };
        }
        if (opts.debug !== "") {
            setInterval(function() {
                // output debug data
                $('#x').html(Math.abs(ax - 2 * axa).toFixed(1));
                $('#y').html(Math.abs(ay - 2 * aya).toFixed(1));
                $('#z').html(Math.abs(az - 2 * aza).toFixed(1));
                $('#shakeaccum').html(shakeaccum);
            },
            10);
        }
    };
})(jQuery);

// plugin default options
jQuery.shake.defaults = {
    // debug div id
    debug: "",
    
    // not supported message div
    supported: "",

    // single shake sensitivity
    violence: 3.0,

    // high-pass filter constant
    hf: 0.2,

    // number of single shakes required to fire a shake event
    shakethreshold: 5,

    // delay between shake events (in ms)
    debounce: 1000,

    // anonymous callback function
    callback: function() {}
};