这个烟花效果，浏览器窗口切换到其他tab页，等一下，再切换回来，烟花效果不正确，怎么改正？
浏览器打开该页面，切换到其他tab页。等几秒再切换回来。烟花会出现倒退效果。怎么改正？
代码不是我写的，canvas也不熟悉，需要大神亲自指明代码。
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<style>
body,html {
overflow: hidden;
margin: 0;
padding: 0px;
}
.opaque {
margin: 0;
width: 100%;
background: #020202;
cursor: crosshair;
}
canvas {
display: block
}
h1 {
position: absolute;
top: 20%;
left: 50%;
transform: translate(-50%, -50%);
color: #fff;
font-family: "Source Sans Pro";
font-size: 5em;
font-weight: 900;
-webkit-user-select: none;
user-select: none;
}
</style>
</head>
<body>
<div class="opaque">
<canvas id="birthday"></canvas>
</div>
<script type="text/javascript">
// helper functions
const PI2 = Math.PI * 2
const random = (min, max) => Math.random() * (max - min + 1) + min | 0
const timestamp = _ => new Date().getTime()
// container
class Birthday {
constructor() {
this.resize()
// create a lovely place to store the firework
this.fireworks = []
this.counter = 0
}
resize() {
this.width = canvas.width = window.innerWidth
let center = this.width / 2 | 0
this.spawnA = center - center / 4 | 0
this.spawnB = center + center / 4 | 0
this.height = canvas.height = window.innerHeight
this.spawnC = this.height * .1
this.spawnD = this.height * .5
}
onClick(evt) {
let x = evt.clientX || evt.touches && evt.touches[0].pageX
let y = evt.clientY || evt.touches && evt.touches[0].pageY
let count = random(3, 5)
for (let i = 0; i < count; i++) this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
x,
y,
random(0, 260),
random(30, 110)))
this.counter = -1
}
update(delta) {
ctx.globalCompositeOperation = 'hard-light'
ctx.fillStyle = `rgba(20,20,20,${ 7 * delta })`
ctx.fillRect(0, 0, this.width, this.height)
ctx.globalCompositeOperation = 'lighter'
for (let firework of this.fireworks) firework.update(delta)
// if enough time passed... create new new firework
this.counter += delta * 3 // each second
if (this.counter >= 1) {
this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
random(0, this.width),
random(this.spawnC, this.spawnD),
random(0, 360),
random(30, 110)))
this.counter = 0
}
// remove the dead fireworks
if (this.fireworks.length > 1000) this.fireworks = this.fireworks.filter(firework => !firework.dead)
}
}
class Firework {
constructor(x, y, targetX, targetY, shade, offsprings) {
this.dead = false
this.offsprings = offsprings
this.x = x
this.y = y
this.targetX = targetX
this.targetY = targetY
this.shade = shade
this.history = []
}
update(delta) {
if (this.dead) return
let xDiff = this.targetX - this.x
let yDiff = this.targetY - this.y
if (Math.abs(xDiff) > 3 || Math.abs(yDiff) > 3) { // is still moving
this.x += xDiff * 2 * delta
this.y += yDiff * 2 * delta
this.history.push({
x: this.x,
y: this.y
})
if (this.history.length > 20) this.history.shift()
} else {
if (this.offsprings && !this.madeChilds) {
let babies = this.offsprings / 2
for (let i = 0; i < babies; i++) {
let targetX = this.x + this.offsprings * Math.cos(PI2 * i / babies) | 0
let targetY = this.y + this.offsprings * Math.sin(PI2 * i / babies) | 0
birthday.fireworks.push(new Firework(this.x, this.y, targetX, targetY, this.shade, 0))
}
}
this.madeChilds = true
this.history.shift()
}
if (this.history.length === 0) this.dead = true
else if (this.offsprings) {
for (let i = 0; this.history.length > i; i++) {
let point = this.history[i]
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,' + i + '%)'
ctx.arc(point.x, point.y, 1, 0, PI2, false)
ctx.fill()
}
} else {
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,50%)'
ctx.arc(this.x, this.y, 1, 0, PI2, false)
ctx.fill()
}
}
}
let canvas = document.getElementById('birthday')
let ctx = canvas.getContext('2d')
let then = timestamp()
let birthday = new Birthday
window.onresize = () => birthday.resize()
document.onclick = evt => birthday.onClick(evt)
document.ontouchstart = evt => birthday.onClick(evt)
;
(function loop() {
requestAnimationFrame(loop)
let now = timestamp()
let delta = now - then
then = now
birthday.update(delta / 1000)
})()
</script>
</body>
</html>如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（2）
定时器异常了吧。
document.hidden隐藏的时候动画就停了呗。监听visibilitychange这个事件是在前后台切换的时候会触发。
附上我以前写的,你可以参考下:
效果:
https://grewer.github.io/JsDe...
code:
https://github.com/Grewer/JsD...