JS缓冲运动与透明渐变
2017-01-04 本文已影响41人
duJing
HTML部分：
<!DOCTYPE html>
<html>
<meta charset="utf-8"/>
<head>
<link rel="stylesheet" type="text/css" href="dome.css"/>
</head>
<body>
<input type="button" value="按钮" id="btn"/>
<div id="box">box</div>
<div id="container"></div>
<script src="../base.js"></script>
<script src="../tool.js"></script>
<script src="dome.js"></script>
</body>
</html>CSS部分：
body {
margin:0px;
padding:0px;
}
#box {
position : absolute;
width : 100px;
height : 100px;
background : red;
left : 100px;
top : 100px;
}
#container {
width : 300px;
height : 500px;
background: #ccc;
}JS部分：
// 跨浏览器获取css样式
function getStyle(element, attr) {
var value = 0;
if (typeof window.getComputedStyle != 'undefined') { // W3C
value = window.getComputedStyle(element, null)[attr];
} else if (typeof element.currentStyle != 'undefined') { // IE
value = element.currentStyle[attr];
}
return value;
}
// 加载DOM
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
var timer = setInterval(function () {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
if (parseInt(getStyle(div, "left")) >= 300) clearInterval(timer);
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, 30);
});
})();这样我们，就可以简单的通过单击按钮使得DIV运动起来，实现简单的动画
接下来，我们将这个简单的动画封装一下下
Base.prototype.animate = function (attr, target, step, t) {
for (var i = 0, len = this.elements.length; i < len; i++) {
var element = this.elements[i];
var timer = setInterval(function () {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
if (parseInt(getStyle(element, attr)) >= target) clearInterval(timer);
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);
}
return this;
}前台调用部分：
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
$("#box").animate("left", 300, 10, 30);
});
})();由于animate()方法的参数计较多，容易混淆，我们该为传个对象，
并且加入增量alter
Base.prototype.animate = function (obj) {
for (var i = 0, len = this.elements.length; i < len; i++) {
var element = this.elements[i];
var attr = obj.attr !== undefined ? obj.attr : "left";
var start = obj.attr !== undefined ? obj.attr : parseInt(getStyle(element, attr));
// 当alter和target同时存在时，忽略alter
var alter = obj.alter;
var target = obj.target;
if (alter !== undefined && target === undefined) {
target = start + alter;
} else if (alter === undefined && target === undefined) {
throw new Error("增量alter或者目标量target两个值必须填一个");
}
var step = obj.step !== undefined ? obj.step : 10;
var t = obj.t !== undefined ? obj.t : 30;
var timer = setInterval(function () {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
if (parseInt(getStyle(element, attr)) >= target) clearInterval(timer);
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);
}
return this;
}前台调用：
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
$("#box").animate({
attr : "left",
start : 100,
alter : 900, // 当alter和target同时存在时，忽略alter
target : 300,
step : 10,
t : 30
});
});
})();问题：当我们将step设置为7的时候，div到达303才能停止，这显然不是我们想要的结果
因此我们在div.style.left >= target时，让其直接等于target
window.timer = setInterval(function () {
if (parseInt(getStyle(element, attr)) >= target) {
element.style[attr] = target + 'px';
clearInterval(timer);
} else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);问题：当div运动到303时，它会自动调回300，这时会有一点卡的感觉
因此我们想要div在296的时候，直接到300，这样更符合。
当div的left属性与target的绝对值小于等于step步长时，我们直接让其等于target
var t = obj.t !== undefined ? obj.t : 30;
window.timer = setInterval(function () {
if (Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
element.style[attr] = target + 'px';
clearInterval(timer);
} else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);问题：当我们不停的单击按钮时，就会不停的触发事件，导致不停的调用定时器，使得div运动的速度越来越快
因此，我们需要将timer放在全局变量中，且在定时器每次被调用时先清除一下
var timer = null; // 将定时器变量放在全局中
Base.prototype.animate = function (obj) {
for (var i = 0, len = this.elements.length; i < len; i++) {
var element = this.elements[i];
var attr = obj.attr !== undefined ? obj.attr : "left";
var start = obj.attr !== undefined ? obj.attr : parseInt(getStyle(element, attr));
// 当alter和target同时存在时，忽略alter
var alter = obj.alter;
var target = obj.target;
if (alter !== undefined && target === undefined) {
target = start + alter;
} else if (alter === undefined && target === undefined) {
throw new Error("增量alter或者目标量target两个值必须填一个");
}
var step = obj.step !== undefined ? obj.step : 10;
var t = obj.t !== undefined ? obj.t : 30;
clearInterval(timer); // 每次才定时器干活前，先把以前的定时器清除掉，防止重复调用
timer = setInterval(function () {
if (Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
element.style[attr] = target + 'px';
clearInterval(timer);
} else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);
}
return this;
}问题：当我们想要让div向左移动时，我们需要将step设置为-7，
且当div的left属性与target的差值小于等于step步的绝对值时，我们让其直接等于target
timer = setInterval(function () {
if (step > 0 && Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
element.style[attr] = target + 'px';
clearInterval(timer);
// 向左向下移动
} else if (step < 0 && parseInt(getStyle(element, attr)) - target <= Math.abs(step)) {
element.style[attr] = target + 'px';
clearInterval(timer);
}else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
document.getElementById("container").innerHTML += getStyle(element, attr) + "<br/>";
}, t);前台调用
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
$("#box").animate({
attr : "top",
start : 100,
target : 0,
step : -7,
t : 30
});
});
})();问题：我们设置step为负时，会感觉很别扭，我们需要让其为正
因此当div的left属性大于target时，我们让step取负
if (parseInt(getStyle(element, attr)) >= target) step = - step;前台调用
$("#box").animate({
attr : "left",
start : 100,
target : 0,
step : 7, // 还是为正
t : 30
});问题：当div的目标值到达了300，我们再次单击按钮时，它就不动了
因此，我们需要设置：当div到达300了，我们让它重置为start，这样它可以重新运动
element.style[attr] = start + ‘px’;
问题：当我们前台调用attr属性为left时，这样不太清晰，我们用x表示left,
y表示top,w表示width,x表示height
var attr = obj.attr === 'x' ? 'left' : obj.attr === 'y' ? 'top' :
obj.attr === 'w' ? 'width' : obj.attr === 'h' ? 'height' : "left";前台调用
$("#box").animate({
attr : "w",
start : 100,
target : 300,
step : 7,
t : 30
});问题：我们需要缓冲运动，这样就使得运动更加的逼真
分析：缓冲运动的意思就是随着div的left属性值与target目标点的差值变小，运动的速度(speed)也逐渐变小
var timer = null;
Base.prototype.animate = function (obj) {
for (var i = 0, len = this.elements.length; i < len; i++) {
var element = this.elements[i];
var attr = obj.attr === 'x' ? 'left' : obj.attr === 'y' ? 'top' :
obj.attr === 'w' ? 'width' : obj.attr === 'h' ? 'height' : "left";
var start = obj.start !== undefined ? obj.start : parseInt(getStyle(element, attr));
// 当alter和target同时存在时，忽略alter
var alter = obj.alter;
var target = obj.target;
if (alter !== undefined && target === undefined) {
target = start + alter;
} else if (alter === undefined && target === undefined) {
throw new Error("增量alter或者目标量target两个值必须填一个");
}
var step = obj.step !== undefined ? obj.step : 10;
if (start >= target) step = - step;
var speed = obj.speed !== undefined ? obj.speed : 6;
var type = obj.type === 0 ? "contant" : obj.type === 1 ? "buffer" : "buffer";
element.style[attr] = start + 'px';
var t = obj.t !== undefined ? obj.t : 30;
clearInterval(timer);
timer = setInterval(function () {
// 缓冲运动
if (type === "buffer") {
var temp = (target - parseInt(getStyle(element, attr))) / speed;
step = step > 0 ? Math.ceil(temp) : Math.floor(temp);
}
// 因为step的范围不可能为0
if (step > 0 && Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
getTarget();
} else if (step < 0 && parseInt(getStyle(element, attr)) - target <= Math.abs(step)) {
getTarget();
}else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
document.getElementById("container").innerHTML += step + "<br/>";
}, t);
function getTarget () {
element.style[attr] = target + 'px';
clearInterval(timer);
}
}
return this;
}前台调用
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
$("#box").animate({
attr : "x",
start : 100,
target : 300,
step : 7,
speed : 5,
t : 30,
type : 1
});
});
})();我们讨论了缓冲运动之后，接下来，我们来讨论一下渐变透明。
当然，这建立在缓冲运动的基础上，我们只需找出动画与渐变透明的不同点即可
首先改变的是css部分：
body {
margin:0px;
padding:0px;
}
#box {
position : absolute;
width : 100px;
height : 100px;
background : red;
left : 100px;
top : 100px;
/*新加的透明度*/
opacity : 0.3;
filter : alpha(opacity = 30);
}
#container {
width : 300px;
height : 500px;
background: #ccc;
}接着，我们进入主题吧
第一步，我们修改attr，用o，代替opacity属性
var attr = obj.attr === 'x' ? 'left' : obj.attr === 'y' ? 'top' :
obj.attr === 'w' ? 'width' : obj.attr === 'h' ? 'height' :
obj.attr === 'o' ? 'opacity' : left;第二步，设置初始值
if (attr === 'opacity') {
element.style.opacity = start / 100;
element.style.filter = "alpha(opacity=" + start + ")";
} else {
element.style[attr] = start + 'px';
}第三步，修改运动
if (attr === 'opacity') {
if (step > 0 && Math.abs(parseFloat(getStyle(element, attr)) * 100 - target) <= step) {
getOpacity();
} else if (step < 0 && parseFloat(getStyle(element, attr)) * 100 - target <= Math.abs(step)) {
getOpacity();
}else {
var temp = parseFloat(getStyle(element, attr)) * 100;
element.style.opacity = (temp + step) / 100;
element.style.filter = "alpha(opacity=" + parseInt(getStyle(element, attr)) + ")";
}
} else {
// 因为step的范围不可能为0
if (step > 0 && Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
getTarget();
} else if (step < 0 && parseInt(getStyle(element, attr)) - target <= Math.abs(step)) {
getTarget();
}else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
}
function getTarget () {
element.style[attr] = target + 'px';
clearInterval(timer);
}
function getOpacity () {
var temp = parseFloat(getStyle(element, attr)) * 100;
element.style.opacity = target / 100;
element.style.filter = "alpha(opacity=" + target + ")";
clearInterval(timer);
}第四步，设置缓冲
if (type === "buffer") {
var temp = attr === 'opacity' ? (target - parseFloat(getStyle(element, attr)) * 100) / speed :
(target - parseInt(getStyle(element, attr))) / speed;
step = step > 0 ? Math.ceil(temp) : Math.floor(temp);
}下面是完整的JS代码：
var timer = null;
Base.prototype.animate = function (obj) {
for (var i = 0, len = this.elements.length; i < len; i++) {
var element = this.elements[i];
var attr = obj.attr === 'x' ? 'left' : obj.attr === 'y' ? 'top' :
obj.attr === 'w' ? 'width' : obj.attr === 'h' ? 'height' :
obj.attr === 'o' ? 'opacity' : left;
var start = obj.start !== undefined ? obj.start :
attr === 'opacity' ? parseFloat(getStyle(element, attr)) * 100 :
parseInt(getStyle(element, attr));
// 当alter和target同时存在时，忽略alter
var alter = obj.alter;
var target = obj.target;
if (alter !== undefined && target === undefined) {
target = start + alter;
} else if (alter === undefined && target === undefined) {
throw new Error("增量alter或者目标量target两个值必须填一个");
}
var step = obj.step !== undefined ? obj.step : 10;
if (start >= target) step = - step;
var speed = obj.speed !== undefined ? obj.speed : 6;
var type = obj.type === 0 ? "contant" : obj.type === 1 ? "buffer" : "buffer";
if (attr === 'opacity') {
element.style.opacity = start / 100;
element.style.filter = "alpha(opacity=" + start + ")";
} else {
element.style[attr] = start + 'px';
}
var t = obj.t !== undefined ? obj.t : 30;
clearInterval(timer);
timer = setInterval(function () {
// 缓冲运动
if (type === "buffer") {
var temp = attr === 'opacity' ? (target - parseFloat(getStyle(element, attr)) * 100) / speed :
(target - parseInt(getStyle(element, attr))) / speed;
step = step > 0 ? Math.ceil(temp) : Math.floor(temp);
}
if (attr === 'opacity') {
if (step > 0 && Math.abs(parseFloat(getStyle(element, attr)) * 100 - target) <= step) {
getOpacity();
} else if (step < 0 && parseFloat(getStyle(element, attr)) * 100 - target <= Math.abs(step)) {
getOpacity();
}else {
var temp = parseFloat(getStyle(element, attr)) * 100;
element.style.opacity = (temp + step) / 100;
element.style.filter = "alpha(opacity=" + parseInt(getStyle(element, attr)) + ")";
}
} else {
// 因为step的范围不可能为0
if (step > 0 && Math.abs(parseInt(getStyle(element, attr)) - target) <= step) {
getTarget();
} else if (step < 0 && parseInt(getStyle(element, attr)) - target <= Math.abs(step)) {
getTarget();
}else {
element.style[attr] = parseInt(getStyle(element, attr)) + step + "px";
}
}
document.getElementById("container").innerHTML += parseFloat(getStyle(element, attr)) * 100 + "<br/>";
}, t);
function getTarget () {
element.style[attr] = target + 'px';
clearInterval(timer);
}
function getOpacity () {
var temp = parseFloat(getStyle(element, attr)) * 100;
element.style.opacity = target / 100;
element.style.filter = "alpha(opacity=" + target + ")";
clearInterval(timer);
}
}
return this;
}前台调用
(function () {
var div = document.getElementById("box");
$("#btn").click(function () {
$("#box").animate({
attr : "o",
start : 30,
target : 100,
step : 6,
speed : 7,
type : 1
});
});
})();
