1 /*
  2  * jquery.fly
  3  *
  4  * 抛物线动画
  5  * @github https://github.com/amibug/fly
  6  * Copyright (c) 2014 wuyuedong
  7  * copy from tmall.com
  8  */
  9 (function ($) {
 10     $.fly = function (element, options) {
 11         // 默认值
 12         var defaults = {
 13             version: '1.0.0',
 14             autoPlay: true,
 15             vertex_Rtop: 20, // 默认顶点高度top值
 16             speed: 1.2,
 17             start: {}, // top, left, width, height
 18             end: {},
 19             onEnd: $.noop
 20         };
 21
 22         var self = this,
 23             $element = $(element);
 24
 25         /**
 26          * 初始化组件，new的时候即调用
 27          */
 28         self.init = function (options) {
 29             this.setOptions(options);
 30             !!this.settings.autoPlay && this.play();
 31         };
 32
 33         /**
 34          * 设置组件参数
 35          */
 36         self.setOptions = function (options) {
 37             this.settings = $.extend(true, {}, defaults, options);
 38             var settings = this.settings,
 39                 start = settings.start,
 40                 end = settings.end;
 41
 42             $element.css({
 43                 marginTop: '0px',
 44                 marginLeft: '0px',
 45                 position: 'fixed'
 46             }).appendTo('body');
 47             // 运动过程中有改变大小
 48             if (end.width != null && end.height != null) {
 49                 $.extend(true, start, {
 50                     width: $element.width(),
 51                     height: $element.height()
 52                 });
 53             }
 54             // 运动轨迹最高点top值
 55             var vertex_top = Math.min(start.top, end.top) - Math.abs(start.left - end.left) / 3;
 56             if (vertex_top < settings.vertex_Rtop) {
 57                 // 可能出现起点或者终点就是运动曲线顶点的情况
 58                 vertex_top = Math.min(settings.vertex_Rtop, Math.min(start.top, end.top));
 59             }
 60
 61             /**
 62              * ======================================================
 63              * 运动轨迹在页面中的top值可以抽象成函数 y = a * x*x + b;
 64              * a = curvature
 65              * b = vertex_top
 66              * ======================================================
 67              */
 68
 69             var distance = Math.sqrt(Math.pow(start.top - end.top, 2) + Math.pow(start.left - end.left, 2)),
 70                 // 元素移动次数
 71                 steps = Math.ceil(Math.min(Math.max(Math.log(distance) / 0.05 - 75, 30), 100) / settings.speed),
 72                 ratio = start.top == vertex_top ? 0 : -Math.sqrt((end.top - vertex_top) / (start.top - vertex_top)),
 73                 vertex_left = (ratio * start.left - end.left) / (ratio - 1),
 74                 // 特殊情况，出现顶点left==终点left，将曲率设置为0，做直线运动。
 75                 curvature = end.left == vertex_left ? 0 : (end.top - vertex_top) / Math.pow(end.left - vertex_left, 2);
 76
 77             $.extend(true, settings, {
 78                 count: -1, // 每次重置为-1
 79                 steps: steps,
 80                 vertex_left: vertex_left,
 81                 vertex_top: vertex_top,
 82                 curvature: curvature
 83             });
 84         };
 85
 86         /**
 87          * 开始运动，可自己调用
 88          */
 89         self.play = function () {
 90             this.move();
 91         };
 92
 93         /**
 94          * 按step运动
 95          */
 96         self.move = function () {
 97             var settings = this.settings,
 98                 start = settings.start,
 99                 count = settings.count,
100                 steps = settings.steps,
101                 end = settings.end;
102             // 计算left top值
103             var left = start.left + (end.left - start.left) * count / steps,
104                 top = settings.curvature == 0 ? start.top + (end.top - start.top) * count / steps : settings.curvature * Math.pow(left - settings.vertex_left, 2) + settings.vertex_top;
105             // 运动过程中有改变大小
106             if (end.width != null && end.height != null) {
107                 var i = steps / 2,
108                     width = end.width - (end.width - start.width) * Math.cos(count < i ? 0 : (count - i) / (steps - i) * Math.PI / 2),
109                     height = end.height - (end.height - start.height) * Math.cos(count < i ? 0 : (count - i) / (steps - i) * Math.PI / 2);
110                 $element.css({
111                     width: width + "px",
112                     height: height + "px",
113                     "font-size": Math.min(width, height) + "px"
114                 });
115             }
116             $element.css({
117                 left: left + "px",
118                 top: top + "px"
119             });
120             settings.count++;
121             // 定时任务
122             var time = window.requestAnimationFrame($.proxy(this.move, this));
123             if (count == steps) {
124                 window.cancelAnimationFrame(time);
125                 // fire callback
126                 settings.onEnd.apply(this);
127             }
128         };
129
130         /**
131          * 销毁
132          */
133         self.destory = function () {
134             $element.remove();
135         };
136
137         self.init(options);
138     };
139
140     // add the plugin to the jQuery.fn object
141     $.fn.fly = function (options) {
142         return this.each(function () {
143             if (undefined == $(this).data('fly')) {
144                 $(this).data('fly', new $.fly(this, options));
145             }
146         });
147     };
148 })(jQuery);