我有定时器功能，有进度条。它工作得很好，但我想制作一个平滑的进度条动画，帧速率为 60 FPS
function started(duration) {
var TotalSeconds = 40;
var documentWidth = $(document).width();
var start = Date.now();
var intervalSetted = null;
function timer() {
var diff = duration - (((Date.now() - start) / 1000) | 0);
var seconds = (diff % 60) | 0;
seconds = seconds < 10 ? "0" + seconds : seconds;
$('#timer').html("00:" + seconds);
var progresBarWidth = (seconds * documentWidth / TotalSeconds);
$('#progress').css({
width: progresBarWidth + 'px'
});
if (diff <= 0) {
clearInterval(intervalSetted);
}
}
timer();
intervalSetted = setInterval(timer, 1000);
}
started(40);
如何实现 60FPS 动画？
这是我的代码的演示：JSFiddle!
您可以使用 CSS3 动画。
我编写了一些示例代码，其中显示了一个进度条，该进度条使用您可以选择的持续时间进行倒计时。您还可以在动画完成时进行回调。
CSS3 动画是硬件加速的，因此您在使用它时将获得最流畅的体验。
/*
* Creates a progressbar.
* @param id the id of the div we want to transform in a progressbar
* @param duration the duration of the timer example: '10s'
* @param callback, optional function which is called when the progressbar reaches 0.
*/
function createProgressbar(id, duration, callback) {
// We select the div that we want to turn into a progressbar
var progressbar = document.getElementById(id);
progressbar.className = 'progressbar';
// We create the div that changes width to show progress
var progressbarinner = document.createElement('div');
progressbarinner.className = 'inner';
// Now we set the animation parameters
progressbarinner.style.animationDuration = duration;
// Eventually couple a callback
if (typeof(callback) === 'function') {
progressbarinner.addEventListener('animationend', callback);
}
// Append the progressbar to the main progressbardiv
progressbar.appendChild(progressbarinner);
// When everything is set up we start the animation
progressbarinner.style.animationPlayState = 'running';
}
addEventListener('load', function() {
createProgressbar('progressbar1', '40s');
createProgressbar('progressbar2', '30s');
createProgressbar('progressbar3', '20s', function() {
alert('20s progressbar is finished!');
});
createProgressbar('progressbar4', '10s', function() {
alert('10s progressbar is finished!');
});
});
.progressbar {
width: 80%;
margin: 25px auto;
border: solid 1px #000;
}
.progressbar .inner {
height: 15px;
animation: progressbar-countdown;
/* Placeholder, this will be updated using javascript */
animation-duration: 40s;
/* We stop in the end */
animation-iteration-count: 1;
/* Stay on pause when the animation is finished finished */
animation-fill-mode: forwards;
/* We start paused, we start the animation using javascript */
animation-play-state: paused;
/* We want a linear animation, ease-out is standard */
animation-timing-function: linear;
}
@keyframes progressbar-countdown {
0% {
width: 100%;
background: #0F0;
}
100% {
width: 0%;
background: #F00;
}
}
<div id='progressbar1'></div>
<div id='progressbar2'></div>
<div id='progressbar3'></div>
<div id='progressbar4'></div>
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