- var funParabola = function(element, target, options) {
- /*
- * 网页模拟现实需要一个比例尺
- * 如果按照1像素就是1米来算,显然不合适,因为页面动不动就几百像素
- * 页面上,我们放两个物体,200~800像素之间,我们可以映射为现实世界的2米到8米,也就是100:1
- * 不过,本方法没有对此有所体现,因此不必在意
- */
- var defaults = {
- speed: 166.67,
- // 每帧移动的像素大小,每帧(对于大部分显示屏)大约16~17毫秒
- curvature: 0.001,
- // 实际指焦点到准线的距离,你可以抽象成曲率,这里模拟扔物体的抛物线,因此是开口向下的
- progress: function() {},
- complete: function() {}
- };
- var params = {};
- options = options || {};
- for (var key in defaults) {
- params[key] = options[key] || defaults[key];
- }
- var exports = {
- mark: function() {
- return this;
- },
- position: function() {
- return this;
- },
- move: function() {
- return this;
- },
- init: function() {
- return this;
- }
- };
- /* 确定移动的方式
- * IE6-IE8 是margin位移
- * IE9+使用transform
- */
- var moveStyle = "margin",
- testDiv = document.createElement("div");
- if ("oninput" in testDiv) { ["", "ms", "webkit"].forEach(function(prefix) {
- var transform = prefix + (prefix ? "T": "t") + "ransform";
- if (transform in testDiv.style) {
- moveStyle = transform;
- }
- });
- }
- // 根据两点坐标以及曲率确定运动曲线函数(也就是确定a, b的值)
- /* 公式: y = a*x*x + b*x + c;
- */
- var a = params.curvature,
- b = 0,
- c = 0;
- // 是否执行运动的标志量
- var flagMove = true;
- if (element && target && element.nodeType == 1 && target.nodeType == 1) {
- var rectElement = {},
- rectTarget = {};
- // 移动元素的中心点位置,目标元素的中心点位置
- var centerElement = {},
- centerTarget = {};
- // 目标元素的坐标位置
- var coordElement = {},
- coordTarget = {};
- // 标注当前元素的坐标
- exports.mark = function() {
- if (flagMove == false) return this;
- if (typeof coordElement.x == "undefined") this.position();
- element.setAttribute("data-center", [coordElement.x, coordElement.y].join());
- target.setAttribute("data-center", [coordTarget.x, coordTarget.y].join());
- return this;
- }
- exports.position = function() {
- if (flagMove == false) return this;
- var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft,
- scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
- // 初始位置
- if (moveStyle == "margin") {
- element.style.marginLeft = element.style.marginTop = "0px";
- } else {
- element.style[moveStyle] = "translate(0, 0)";
- }
- // 四边缘的坐标
- rectElement = element.getBoundingClientRect();
- rectTarget = target.getBoundingClientRect();
- // 移动元素的中心点坐标
- centerElement = {
- x: rectElement.left + (rectElement.right - rectElement.left) / 2 + scrollLeft,
- y: rectElement.top + (rectElement.bottom - rectElement.top) / 2 + scrollTop
- };
- // 目标元素的中心点位置
- centerTarget = {
- x: rectTarget.left + (rectTarget.right - rectTarget.left) / 2 + scrollLeft,
- y: rectTarget.top + (rectTarget.bottom - rectTarget.top) / 2 + scrollTop
- };
- // 转换成相对坐标位置
- coordElement = {
- x: 0,
- y: 0
- };
- coordTarget = {
- x: -1 * (centerElement.x - centerTarget.x),
- y: -1 * (centerElement.y - centerTarget.y)
- };
- /*
- * 因为经过(0, 0), 因此c = 0
- * 于是:
- * y = a * x*x + b*x;
- * y1 = a * x1*x1 + b*x1;
- * y2 = a * x2*x2 + b*x2;
- * 利用第二个坐标:
- * b = (y2+ a*x2*x2) / x2
- */
- // 于是
- b = (coordTarget.y - a * coordTarget.x * coordTarget.x) / coordTarget.x;
- return this;
- };
- // 按照这个曲线运动
- exports.move = function() {
- // 如果曲线运动还没有结束,不再执行新的运动
- if (flagMove == false) return this;
- var startx = 0,
- rate = coordTarget.x > 0 ? 1 : -1;
- var step = function() {
- // 切线 y'=2ax+b
- var tangent = 2 * a * startx + b; // = y / x
- // y*y + x*x = speed
- // (tangent * x)^2 + x*x = speed
- // x = Math.sqr(speed / (tangent * tangent + 1));
- startx = startx + rate * Math.sqrt(params.speed / (tangent * tangent + 1));
- // 防止过界
- if ((rate == 1 && startx > coordTarget.x) || (rate == -1 && startx < coordTarget.x)) {
- startx = coordTarget.x;
- }
- var x = startx,
- y = a * x * x + b * x;
- // 标记当前位置,这里有测试使用的嫌疑,实际使用可以将这一行注释
- element.setAttribute("data-center", [Math.round(x), Math.round(y)].join());
- // x, y目前是坐标,需要转换成定位的像素值
- if (moveStyle == "margin") {
- element.style.marginLeft = x + "px";
- element.style.marginTop = y + "px";
- } else {
- element.style[moveStyle] = "translate(" + [x + "px", y + "px"].join() + ")";
- }
- if (startx !== coordTarget.x) {
- params.progress(x, y);
- window.requestAnimationFrame(step);
- } else {
- // 运动结束,回调执行
- params.complete();
- flagMove = true;
- }
- };
- window.requestAnimationFrame(step);
- flagMove = false;
- return this;
- };
- // 初始化方法
- exports.init = function() {
- this.position().mark().move();
- };
- }
- return exports;
- };
- // 这是很简单的拖拽方法,与本demo主旨无关,方便演示使用
- var funDrag = function(element, callback) {
- callback = callback ||
- function() {};
- var params = {
- left: 0,
- top: 0,
- currentX: 0,
- currentY: 0,
- flag: false
- };
- //获取相关CSS属性
- var getCss = function(o, key) {
- return o.currentStyle ? o.currentStyle[key] : document.defaultView.getComputedStyle(o, false)[key];
- };
- //拖拽的实现
- if (getCss(element, "left") !== "auto") {
- params.left = getCss(element, "left");
- }
- if (getCss(element, "top") !== "auto") {
- params.top = getCss(element, "top");
- }
- //o是移动对象
- element.onmousedown = function(event) {
- params.flag = true;
- event = event || window.event;
- params.currentX = event.clientX;
- params.currentY = event.clientY;
- };
- document.onmouseup = function() {
- params.flag = false;
- if (getCss(element, "left") !== "auto") {
- params.left = getCss(element, "left");
- }
- if (getCss(element, "top") !== "auto") {
- params.top = getCss(element, "top");
- }
- callback();
- };
- document.onmousemove = function(event) {
- event = event || window.event;
- if (params.flag) {
- var nowX = event.clientX,
- nowY = event.clientY;
- var disX = nowX - params.currentX,
- disY = nowY - params.currentY;
- element.style.left = parseInt(params.left) + disX + "px";
- element.style.top = parseInt(params.top) + disY + "px";
- }
- }
- }; (function() {
- var lastTime = 0;
- var vendors = ['webkit', 'moz'];
- for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
- window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
- window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] || // name has changed in Webkit
- window[vendors[x] + 'CancelRequestAnimationFrame'];
- }
- if (!window.requestAnimationFrame) {
- window.requestAnimationFrame = function(callback, element) {
- var currTime = new Date().getTime();
- var timeToCall = Math.max(0, 16.7 - (currTime - lastTime));
- var id = window.setTimeout(function() {
- callback(currTime + timeToCall);
- },
- timeToCall);
- lastTime = currTime + timeToCall;
- return id;
- };
- }
- if (!window.cancelAnimationFrame) {
- window.cancelAnimationFrame = function(id) {
- clearTimeout(id);
- };
- }
- } ());
来源: http://www.bubuko.com/infodetail-1946403.html